Our Glossary is a hybrid of terms and descriptions from a variety of disciplines and sources in acoustics, audio/video (A/V), physics, electrical, psychoacoustics, film & entertainment, and other assorted fields of endeavor.
Absorption – Indicates the sound absorbing characteristics of a material. It is the portion of energy absorbed when a sound wave strikes a material. Measured in Sabine units, an absorption co-efficient of 1.0 = total absorption, and 0.0 = total reflection. Each and every room has its own unique acoustic character. Left acoustically untreated, rooms will create unwanted sound effects that can distract or remove the prospects of ever reproducing the experience that a film director, the music conductor, and games developer intended. An acoustic specialist knows how to identify the sound waves to encourage, those you want less of, and those that you want to remove altogether. A variety of absorption techniques are considered and applied as needed to create the overall sensation of sonic clarity necessary to an Immersive RealismTM experience.
Acoustics – is how sound acts in a given space, such as within a room. The way that sound waves are reflected and absorbed by a room gives the room a unique sound characteristic or coloration. A room’s acoustics contribute to its ambiance. Acoustics is also the science or study of sound and sound behavior.
Acoustic environment – The sum total of all objects and their respective physical properties forming the sound field that surrounds the listener. The room and its dimensions is the primary component in the influence of the sound field determining the qualities of a listener’s experience. Loudspeakers are sources for the transmission of sound waves inside the acoustic environment (e.g. – room dimensions + objects + physical properties of those objects + A/V loudspeaker design properties). 2) A listener receives sound waves from loudspeakers via a multiplicity of directions. Acouticians describe this effect by the number of reflections to reaching the listener (i.e. a single bounce off an environment object is a “first-order” reflection, two bounces a “second-order” reflection,” and so on). 3) Each time a sound wave reflects off an object the energy of that waveform is changed. This “change” happens as a result of coming in contact with any and all objects in the environment while the sound wave expends its energy. The term “Absorption Coefficient” is used to describe the myriad of material surfaces (i.e. – floor, seating, wall, ceiling, and furnishings) and the amount of energy these surfaces absorb and how much is reflected back into the environment. 4) One final consideration, the geometry or shape of materials (e.g. – edges, concave, convex, openings, etc.) provide their own complex influence and effect of sound waves. To review an illustration of reflection, absorption, and diffusive treatment used in taming sonic gremlins [click here].
Aesthetics – 1) the engaging of the mind and emotions to elicit a connection to and involvement with that which people find beautiful and attracted to. 2) A goal or outcome from collaboration between architects, interior designers and A/V lifestyle specialists marked by thoughtful, balanced attention to each discipline to deliver compelling, immersive experiences for clients where audio, video, and acoustical technologies are showcased.
Ambiance – how a room sounds or feels. It is 1) the unique acoustical characteristics of a room. These characteristics are determined by the room’s particular acoustic properties, such as reverberation and reflections. A concert hall or a cathedral has a different ambiance than a gymnasium. Terms such as lively, dead, warm, cold, or brilliant are often used to describe a room’s ambiance, 2) The subtle, low-level natural sounds such as wind, rustling leaves that characterize a particular place, and 3) ambience can also include non-audio aspects of a place, such as smells and visual images.
Ambience – The residual “room sound” of a listening environment. In classical music, for example, the term ambience is used interchangeably with the word reverberation, to refer to the persistence of decaying sounds in the listening room. Not to be confused with ambient noise, which refers to background noise. The subjective determination by an individual of how pleasant a listening space is perceived to be.
Ambient Light – All light in a viewing room produced by sources other than the screen.
Anamorphic – Films have never fit the television screen easily and it’s always been that way. To fit the film onto a viewing screen, without the dimensions of a theater screen, this process horizontally condenses (squeezes) the cinema image into other screen sizes. For a 4:3 TV screen this squeezing preserves 25% more vertical resolution than the technique called “letter-boxing.” For the video signal to have the correct geometry the display must either vertically squish or horizontally expand the film image. Anamorphic is often used with DVDs. Other non-anamorphic methods for film content to TV screens and other aspect ratios involves modifying the image to fit the aspect ratio (like letter boxing) which removes content from the film to fit the aspect ratio for presentation. Anamorphic lenses procedures preserve most of the director’s content.
Artifacts, Picture – One of the 6 key elements supporting peak performance in video displays, an artifact is a defect or distortion of the image, introduced along the sequence from origination and image capture to final display. In video, it is a distortion of any part of the image rendered on your display. 2) Artifacts are more easily recognized by the names we give them – motion artifacts, cross color, color blemishes, and jaggies are a few of them. 3) An artifact may occur naturally in the post-production process of viewing content but must be eliminated to produce a high-quality picture. Artifacts are also produced by a change in the video signal path as it moves from the video source (i.e. a satellite, cable, your DVD) over the interconnect into your video display where it is finally rendered on the screen. Things can happen anywhere along the path. Where an calibration specialist can find the cause it can be removed or minimized. 4) Don’t confuse this term with not having the video display properly calibrated. This is a distortion of a related-kind. 5) Video processing – a.k.a. up-converting images – from one aspect ratio (say, NTSC TV 4:3) to another higher resolution (say, 16:9 widescreen) format can produce artifacts, too.
Aspect Ratio – the relationship of the horizontal dimension to the vertical dimension of a rectangle. In viewing screens, standard TV is 4:3, or 1.33:1; HDTV is 16:9, or 1.78:1. Sometimes the “:1” is implicit making TV = 1.33 and HDTV = 1.78. Movies studios have over the years created wider aspect ratios for film to differentiate their films from, initially, those that would be shown on TV (i.e. get you into the movie theater, again) and to compete against other studios in producing more life-like, immersive film experiences. For HDTV to show any film the film has to be adapted to fit the 16:9 (1.78:1) viewing screen by the movie studio owning the film. Here are the most prevalent aspect ratios of movie studios:
- Cinerama® (2.65:1 – 3.00:1)
- CinemaScope® (2.35:1)
- 70mm (2.05:1)®
- VistaVision® (1.85:1)
- Panavision® (1.85:1) – the most common
Automatic Convergence – The automatic alignment of the red, green and blue color images.
AVG– Short for Audio/Video/Gaming. Used to describe the electronic equipment installed for experiences in home theater, music listening, or playing interactive games.
A/V Receiver (Surround Receiver) – the main component in a home theatre system. The A/V receiver performs several critical functions: 1) accepts the signals from various sources (DVD, VCR, satellite receiver etc.), 2) selects the desired signal, 3) provides surround sound decoding, 4) provides volume control, 5) provides power amplification to drive the speakers.
A/V System – A term to describe a collection of electronic components connected together by audio and video interconnect cabling for playback of source materials such as DVD movies. The minimum configuration for an A/V system capable of playback of DVD movies according to Dolby® Digital 5.1 standards is comprised of 1) an A/V receiver with Dolby® Digital 5.1 circuitry, 2) five (5) loudspeakers including 3 matching loudspeakers providing F (Front) channel, C (Center) channel, and R (Right) channel sound, and 2 matching loudspeakers providing surround sound, and 3) a subwoofer providing lower Hz bass sounds. By connecting a high-definition video display you now have an A/V system capable of playing widescreen movies from DVD.
Balance – is described as 1) how closely the volume levels (sound pressure levels) produced by two or more sound sources (such as speakers) match when each is driven with the same signal. The two speakers in a stereo system must be able to produce the same volume levels with identical inputs for a system to produce good stereo separation, 2) the term that describes the overall process of setting or calibrating the levels in a sound system, and 3) a control that is used to adjust the signal level between two channels.
Bass – the lowest frequencies of the audio spectrum below approximately 500 Hz. Bass frequencies have the longest wavelengths and are typically reproduced with large drivers called woofers. The bass band is sometimes subdivided into low bass (below approximately 80 Hz), mid bass (approximately 80 Hz to 200 Hz) and high bass (approximately 200 to 500 Hz). Subwoofers are used reproduce frequencies below about 100 Hz.
Black Level (Video) – Light level of the darker portions of a video image. A black level control sets the light level of the darkest portion of the video signal to match that of the display’s black level capability. Black is, of course, the absence of light. Many displays, however, have as much difficulty shutting off the light in the black portions of an image as they do creating light in the brighter portions. CRT-based displays usually have better black levels than DLP, plasma, and LCD, which rank, generally, in that order.
Brightness – For video, the overall light level of the entire image. Brightness is a term best used to define the black level of the video display’s image processing (see Black Level). For audio, something referred to as bright has too much treble or high-frequency sound.
Brightness, Excessive (Video) – is evident in most, if not all, CRTs, LCDs, Plasma, and Projection Display technologies through no fault of the consumer but the manufacturers of these devices. Of greater concern to them is attracting customers. To do that on the retail showroom floor they make factory adjustments and add circuitry to increase the appeal of their displays. What looks good in the showroom is usually very different at home watching your favorite films. Displays need to be ISF-calibrated “out-of-the-box” and at intervals through its use to produce the best images that display can produce. Curious to some, to adjust brightness of a video display is to adjust the black levels. The disadvantages of excessive brightness go far beyond what can be perceived by the human eye, namely:
- Increases the sensitivity of the display to field flicker, an annoying and eye fatiguing effect.
- Defocuses the video display leading to degrading imaging performance.
- Specifically on CRTs and Plasmas – excessive brightness increases wear and burn-in.
- Pushes digital imaging displsys into white compression – a loss of overall image quality.
- Shortens the video display’s life.
Clarity – is one of the five (5) sonic goals of any theater system as described by HAA (Home Acoustics Association). Clarity is the prime acoustic goal because its perfection depends on the successful attainment of all other goals. Of paramount importance is dialogue intelligibility in movies, but one must be able to understand musical lyrics, detect quiet background details, and sense realism for acoustic sounds. Elements that affect this goal are varied including equipment quality, room reverberation, ambient noise levels, and listener position, among others.
Color Accuracy (Video) – One of the 6 key elements supporting peak performance in video displays has a lot to do with the ability of the display to render black & white. Experts in color will tell you that we humans are black and white beings capable of seeing things in color. In video, the black and white portion of the video signal contains the majority of the picture information. Your programming content’s color is much like painting on a canvas of black & white. Peak performing video displays have the ability to render images as though you were looking outside through a window at beautifully landscaped gardens noting the nuances of color in the proper perspectives. A video display with difficulty rendering colors is often prompted by a less-than peak performing black & white video electronics. If this were not enough, certain display technologies have a more inherently difficult time producing color accuracy because of the way their “light” engines render black & white colors. Yes, sometimes we forget that black and white are colors, too. In fact they and their gradients/shades truly are arguably the most important “colors.”
Coloration – any audible change in the character of sound. Coloration often refers to changes that make a sound more pleasing, but any coloration alters the sound from its original form. Room interaction and speaker distortion are common sources of sound coloration.
Component Video – 1) Our color television system starts with three channels of information, Red, Green, & Blue (RGB). In the process of translating these channels to a single composite video signal they are often first converted to Y, R-Y, and B-Y. Both 3-channel systems, RGB and Y, R – Y, B – Y are component video signals. They are the components that eventually make up the composite video signal. Much higher program production quality is possible if the elements are assembled in the component domain. 2) Component video is a newer format of video signal that takes the advancement from composite (1-signal) to S-Video (2-signals) one step further. It has separated luma (brightness) and chroma (color), but the chroma is also separated into two signals, red and blue. 3) The result is a triple-headed cable of three RCA connectors and an image cleaner than composite with less color bleeding that S-Video. Although common on newer DVD players and high-end HDTV’s, component video is very rare on standard TV sets and VCR’s.
Component Video – the most common type of jack for hooking up high-definition TVs to set-top tuners or cable and satellite receivers, component-video connections have three (3) RCA-type connectors color-coded red, green, and blue. Component-video signals can also be routed using BNC and VGA connections, but these configurations tend to be rare.
Component Video Format – widely used in professional video prodcution before it trickled down to consumer gear when the DVD scene. The term “component video” itself actually encompasses a number of things. When a video camera records an image, it consists of three (3) channels of color information, again – red, green, and blue. These “components” are compressed into a single channel to form a “composite” video signal for analog TV broadcasting. 2) For digital TV broadcasting, digital satellite transmission, and DVD mastering, however, those three color components are translated into a full-bandwidth brightness channel and two color-difference channels. The reason for this is simple. Keeping color and brightness signals separate prevents cross-color artifacts (the rainbow patterns you sometimes see in a news anchor’s striped tie or tweed jacket) and delivers a dramatic boost in quality over composite video, especially in the color portions of images, which look more solid and detailed. It also saves greatly on channel capacity, since the color-difference signals don’t carry anywhere near the amount of detail that the brightness signal does.
Compression – process of limiting the dynamic range of an audio signal. Compression condenses information so that it can fit into less space. Most audio compression includes reducing the loudest peaks and increasing the softest levels during the record process. The compressed information is decompressed to its original form during playback. Compression is called lossy if some of the original information is lost and the decompressed information does not match the original audio. The compression techniques used in Dolby Digital and DTS are lossy, as these formats discard audio information that can not be heard.
Connectivity – TV has entered the digital era with literally hundreds of channels providing programming content along with HDTV broadcasts running alongside analog ones in most cities. Older analog forms of cabling – namely component video and RGB – were unacceptable to Hollywood studios who bristled at the idea of transmitting theater-quality versions of their movies over unprotected analog connections.which a technically adept “pirate” could tap to make copies for mass distribution. This is a major reason for digital interfaces such as DVI, HDMI, and Firewire 1394. 2) It’s important that any digital TV and HD display come with a full array of connections – component, DVI, HDMI, and Firewire to be adapted to current and future copy-protection schemes. To not have this connectivity will obsolete your TV/display to fewer choices of HD programming content.
Convergence – is the beam-position accuracy of the red, green, and blue beams of a color monitor or projector. Color systems require exact accuracy of beams, both for position and speed, to properly produce the desired colors from their phosphors. 2) A cross-color defect characteristic of NTSC composite video manifests itself as spurious rainbow patterns on highly textured objects like the one found on a striped shirt or tweed jacket. Cross-color defect is attributed to the make-up of the signal which mixes the high luminance and chrominance information in the same composite base band spectrum. Johnny Carson purposely selected ties with designs specifically designed to create this effect. 3) For years the phrase “digital convergence” was a bit hollow. Today it is showing up all over the business landscape. The market for personal digital assistants, so hot in the late ’90s, is vanishing as customers get the same functions in a cell phone — often with a camera to boot. The latest televisions from Royal Philips Electronics and Sony Corp. have enough computing firepower to grab streaming video off the Net. “Convergence is finally really happening,” says Gottfried Dutiné, an executive vice-president at Philips. “Digitalization is creating products that can’t be categorized as tech or consumer electronics. The walls are coming down.” – Business Week, June 21, 2004.
Critical Band – a narrow band of audio frequencies that are summed together by our ears. When several tones within a critical band are played simultaneously, the auditory system does not hear them completely independently. The designated tone may be masked by the other tones, or a beat may be heard. Noise that is within a critical band can mask a tone within the same band even if the noise level is below the level of the tone. When presented with two tones close in frequency and having similar SPL levels, our ears hear them as a beat rather than as two separate tones. As the tones are separated in frequency, the perceived loudness suddenly increases and two separate tones can be heard. The range of frequencies where the perceived loudness remained the same and a beat was heard is the ear’s critical bandwidth. The ear’s critical bandwidth changes with frequency. It is about 90-100 Hz wide for frequencies below 500 Hz, and about 1/6 octave wide at higher frequencies. Sounds that fall within the same critical band excite the same group of nerves in the ear.
Decibel – A unit of the intensity of sound. The decibel (abbreviated dB) is a relational measure, expressing the relative intensity of the described sound to a reference sound. The decibel is a logarithmic measure, specifically 10 times the logarithm of the ratio of two voltages, currents or sound pressures. A difference of 20 dB between two sounds means that the more intense one has 10 times the amplitude (100 times the power) of the softer. A single decibel is commonly thought to be the smallest change in sound pressure level that the trained human ear can detect.
Definition – a subjective term that describes a characteristic of sound and room ambience. Definition refers to how well the individual notes in a musical presentation can be differentiated from each other. Reverberation time and intensity affect definition. Definition is similar to clarity. In concert hall acoustics, definition, like clarity, refers to the degree to which individual strands in a musical presentation can be differentiated from each other. There are two kinds of definition: horizontal, which applies to tones played in succession; and vertical, in which tones are played simultaneously.
Delay – 1) The result of sound waves needing to travel some distance before reaching your ear. Delay gives the perception of spaciousness and is the result of the time difference between direct and reflected sounds. 2) An electronic technique that is used to change how long it takes for a sound to reach your ears. Delay is added to signals so that the sounds arriving from one speaker match the sounds arriving from another speaker that is further away. To work properly and not sound like an echo, the delay must be short enough (<= 30 milliseconds) so that your ear cannot distinguish between the two. Delay is used to recreate the ambience of a specific environment, and can be set on surround sound processors to create the desired effect. 3) The time difference between when a front speaker plays a sound and a rear or surround speaker plays a corresponding sound. Most surround sound processors provide adjustable delay.
Depth – the characteristic of a sound that relates to the sense of spaciousness. Depth makes a sound seem more life-like. Sounds that have depth seem to come from in front of and behind the physical speakers, giving the listener the sense that musicians are sitting at differing distances from him. Depth is affected by the sound system and room acoustics.
Diffusion – is the acoustic technique of scattering sound waves to reduce a sense of sound positioning. Each and every room has its own unique acoustic character. Left acoustically untreated, rooms will create unwanted sound effects that can distract or remove the prospects of ever reproducing the experience that a film director, the music conductor, and games developer intended. An acoutician knows how to identify the sound waves to encourage, those you want less of, and those that you want to remove altogether. Diffusion technologies are used to take certain hot spots (a.k.a. concentrated, out-of-balance sounds) found in a room and scatter (rather than reflect or absorb) the sound. 2) A diffusor is an acoustical treatment that preserves hot-spot sound energy by reflecting it evenly in multiple directions, as opposed to a flat surface, which reflects the majority of the sound energy in one direction.
Digital Audio – audio information that has been encoded into digital bits of information. Digital audio signals are almost immune from distortion and noise (distortion and noise can be a problem when they are converted back to analog for playback however) and are easy to store without signal degradation. Digital audio can be compressed to save space and is easy to manipulate with digital processing. An analog-to-digital converter is used to digitize analog signals. To digitize an audio signal the waveform is sampled in many small pieces. The more samples that are taken, the higher the resolution of the reconstructed signal. The amplitude of each sample is represented by a certain number of data bits. The number of data bits affects how well the reconstructed waveform matches the original. CDs use a sampling rate of 44.1 kHz and 16 data bits (16 bits allows 65,536 amplitude steps). Digital audio signals are decoded by a digital-to-analog converter that recreates the analog audio signal for playback.
Dipole Speaker – type of loudspeaker that radiates sound equally in two directions using drivers mounted opposite each other and operating out of phase (one driver moves in and the other moves out). This creates a broad, spread-out, “figure 8” shaped sound field that seems to come from all directions, making the speakers hard to localize. Dipolar speakers are often used as surround channel speakers and are the only speaker type certified for use as THX surround channel speakers. Dipole speakers are similar to bipole speakers, except bipole speakers operate in phase.
Directivity – how well a sound source can be localized. Directivity is the perception of where a sound is coming from. A directive speaker radiates sound in a straight path to the listener, while speakers having little directivity create a diffuse, all around sound that is not hard to localize.
Distortion – any difference between the applied signal and the reproduced signal. Distortion is a deviation from what is desired and occurs anytime the output does not follow the input. Amplifiers and speakers can produce audible amounts of distortion. Common types of distortion are harmonic distortion, phase distortion and intermodulation distortion.
DLP (Digital Light Processing) – is 1) a technology used in projectors and projection televisions. DLP was originally developed by Texas Instruments who remain the sole manufacturer of such technology though many licensees market products based on their chipsets. In DLP projectors, the image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one pixel in the projected image. The number of mirrors corresponds to the resolution of the projected image: 800×600, 1024×768, and 1280×720 matrices are some common DMD sizes. 2) Earlier projectors used single chips with colors produced by placing a color wheel between the lamp and the DMD chip where it is reflected out through the optics. This approach was prone to producing video artifacts and gray-level viewing variability. 3) Current three-chip projection gives each primary color its own DMD chip then the colors are recombined and routed through the lens avoiding the “rainbow-effect” of one chip systems. DLP technology is growing rapidly in the business presentations, home theater, and rear-projection TV markets. See DMD.
DLP (Rainbow Effect) – Did you hear the story of how baseball’s Babe Ruth could read the print label atop the 78 vinyl record while it was spinning? A subset of the video viewing population has the visual acuity to discern how 1-chip DLP projectors render color through the color wheel of that projector. The effect can be annoying from fatiguing these viewer’s eyes and not knowing why to being unable to watch a video projected from the projector for but a short period of time. This “flashing of color spectrum” should be your clue to consider a 3-chip DLP projector, LCD or other display technology for your viewing needs.
DMD (Digital Micromirror Device) – In 1977, it was originally called “Deformable Mirror Device”. Texas Instruments developed DMD microchips used in DLP (Digital Light ProcessingTM) projectors. With broad support of manufacturers and evolving 3-chip advancements, that all but remove the rainbow effect, DMD/DLP chipsets have become the most prevalent display technology for higher-end projection systems today (2005). DMD chips use an array of mirrors and memory cells. A digital image is stored in the memory, and then projected when light is reflected onto the mirrors.
Dolby Digital® – most widely used digital surround sound format that uses Dolby AC-3 compression. Dolby Digital provides six channels of digital audio information: left front, center front, right front, left surround, right surround, and a Low Frequency Effects (LFE) channel. All of the channels, except the LFE channel have a full audio bandwidth of 20 Hz to 20 kHz. For this reason the Dolby Digital format is sometimes called a 5.1 digital audio format.
Dolby Digital AC-3® – original name for the current Dolby Digital surround sound format that uses the Dolby AC-3 compression scheme. This digital compression scheme, developed by Dolby Laboratories, compresses multiple channels of information into the space normally required for one channel. Dolby Digital has a bitstream of 384 kB/sec for 6 channels of audio information, compared to 1.4 mB/sec for a conventional stereo audio CD. To achieve this compression the audio content of each channel is carefully analyzed and sounds that cannot be perceived by the ear (such as a bird chirping during an explosion) are discarded. This is called perceptual encoding. Dolby Digital achieves a compression ratio of about 10:1 without a perceivable change in sound quality. Dolby AC-3 is now called Dolby Digital.
DVD (Digital Versatile Disc) – previously called Digital VideoDisc. A DVD is a digital storage median that is very similar in appearance to a compact disc. Like a CD, DVDs store information as optical data. However DVDs are capable of storing 25 times more data, and are used for holding both digital video and audio information. Information can be stored on just one side of the disc, on two layers on one side of the disc, on two sides of the disc, or on two layers on both sides of the disc.
DVI (Digital Visual Interface) – is a one-way jack that’s used to route digital bitstreams from a set-top box to a video display. Physically, it looks like a bigger version of VGA, with a D-shaped connector housing a formation of 18 pins. 2) DVI connections transmit signals in uncompressed form. Since no consumer video decks are capable of recording uncompressed high-definitions programs, this means no copying. The Hollywood studios like this idea even if it is not consumer friendly. That said, DVI can offer potential impage quality benefits since they eliminate unnecessary digital-to-analog conversion steps for signals being sent to video displays. See HDCP (High-Bandwidth Digital Content Protection).
Dynamics – is one of the five (5) sonic goals of any theater system as described by HAA (Home Acoustics Association). Dynamics is simply described as the difference between the softest and the loudest sounds reproducible by a sound system. While much emphasis is placed on the loudness side, the audibility of the softest sounds is an equal measure of system performance. Among the acoustic requirements for proper envelopment, focus, and clarity is the necessity of hearing the sonic cues relating these qualities. If they are overwhelmed by excessive ambient noise or reverberation in a room, they’re not properly audible. At a minimum, a system must be capable of reproducing loud passages with ease and without excess while soft sounds remain easily audible.
Dynamic Range – a range that is expressed in decibels; 1) the range between the loudest and softest sounds in an audio program. 2) the range between the highest or loudest levels and the lowest or softest levels that a sound system or component can reproduce. Exceeding the highest level creates distortion. The lowest reproducible level is limited by the noise floor. 3) is the difference between loud and soft, and the difference between bright and dark.
Dynamic Range (video) – describes well-behaved, consistent adherence to the 6 key elements in peak performing video displays and the pictures they render, namely – 1) picture resolution, 2) picture contrast, 3) color accuracyc 4) picture uniformity, 5) picture geometry, and 6) no artifacts. It is also another way to describe the difference between the minimum and maximum signal range that a video display can reproduce. A video display performing inside the dynamic range contributes to a peak experience in the “Magic Quadrant” of Hi-Definition Living’s immersive realism©. Most, if not all, video displays will require periodic adjustments to perform inside the dynamic range – clear, crisp and accurate grayscale with life-like, accurate colors in sharp, detailed picture resolution.
Early reflections – reflected sound waves that arrive at the listener less than 5 milliseconds after the direct sound. Early reflections are caused by sound waves bouncing off of a surface that is within about 5 feet of the loudspeaker. Early reflections that are too loud compared to the direct sound at the listener’s ear can confuse the listener’s ability to localize the sound source. This results in false stereo imaging, poor sound clarity, and a very narrow soundstage. See late reflections.
Envelopment – is one of the five (5) sonic goals of any theater system as described by HAA (Home Acoustics Association). An audio system should reproduce virtual images of each recorded sound, presenting the listener with its apparent source location in a three-dimensional space. Each sonic image relates a part of the recorded event; together, these sounds compose a wraparound soundstage that envelops the listener. Proper envelopment requires that the soundstage be seamless for 360-degrees without interruption by holes or hot spots caused by speaker-level imbalance or poor placement. While envelopment requires three-dimensional imaging of all sonic cues, of pivotal importance is the realistic re-creation of the recorded venue’s ambient soundfield. Focused sounds become more realistic as they move side-to-side and front-to-back with the backdrop of the intended venue’s ambient sounds.
Equalization – is the process of adjusting the frequency response of an audio signal to achieve a desired (usually flat) response. Equalization is often used to correct for room interactions, but it should not be used as a substitute for proper room and system setup.
FireWire 1394 – are two-way connections (unlike DVI) that can be used to route both audio and video. The connections are relatively small, compared to other formats (like DVI) and come in both 4- and 6-pin connections. FireWire connections on digital TVs and set-top boxes support a copy-protection scheme called DTCP (Digital Transmission Content Protection) that’s considerably more flexible than the HDCP scheme used for DVI. With DTCP, for example, a movie transmitted in high-def over satellite or cable could be embedded with speciific instructions that allow a digital VCR to make one, several, or unlimited copies of the program. But for premiium content like pay-per-view movies where greateer security is desired, similar codes could be used to block recording altogether.
5.1 (Five point one) – the name sometimes given to the DTS and Dolby Digital surround sound audio formats. These formats provide 6 channels of sound information – left front, front center, right front, right surround, left rear surround, and Low Frequency Effects (LFE). All channels except the LFE channel have a 20 Hz – 20 kHz frequency response. The LFE channel only handles bass frequencies from 3 Hz to120 Hz for reproducing low bass effects. Since this frequency range is approximately one-tenth the bandwidth of the other channels, it is known as the “point one” channel and these formats are called 5.1.
Flat Response – all frequencies having the same level across the audio frequency spectrum. The energy-frequency graph of flat response is a flat line with less than ±1 dB variation. While a flat response is ideal for an audio system, it is impossible to obtain due to the limited frequency response of speakers and the effects of room interaction. A frequency response is considered flat if it deviates within a small, specified amount over a specified frequency range.
Focus – is one of the five (5) sonic goals of any theater system as described by HAA (Home Acoustics Association). Acoustic focus is the ability to precisely locate each reproduced sonic cue or image in a three-dimensional space. Recordings contain many such images superimposed side-to-side and front-to-back in every direction for 360 degrees around the listener. A system is said to have pinpoint focus if, from the listener’s perspective, each of these images is properly sized, precisely located, and not wandering. Good focus also means that individual images are easily distinguishable from amongst others within the limits of the recording’s quality.
Foley – is 1) the art of recreating incidental sound effects, such as footsteps or rustling clothes, in sync with the picture. Foley artists are unsung geniuses who create the larger-than-life sound effects breathing additional life into a film. To produce the sound of a face punch the Foley artist might hit a piece of raw meat with his fist, maybe wearing a tight leather glove for enhanced “smackiness.” Rib cuts are particularly good because they have bones to give a crunching effect. If you get the feeling that there are no rules – you’re right. If it works on-screen it works, period. 2) Foley art is necessary because you need ambient sounds (more than the actor’s dialogue) to make the movie scene seem real. Also, miking the entire sound stage or location for the shoot just isn’t practical. Real sounds often don’t pack the punch the big screen demands. In addition, dubbing for foreign markets frequently require that a sound track be recreated from scratch.
Foot Lambert – The luminance (brightness) resulting from a surface emitting a luminance flux of one lumen per square foot. The luminance of a perfectly reflecting surface receiving an illumination of one foot-candle.
4:3 (Four Three) – 1) The 50+ year old NTSC video standard used in the original analog TV sets. This aspect ratio is being slowly phased out in favor of the wider, more panoramic and movie-like 16:9 aspect ratio. Video displays using a 4-by-3 ratio display images 4 units wide (horizontal) by 3 units tall (vertical). 2) The 4:3 aspect ratio is fine for content created for TV but cinema, the movies developed to be viewed at theaters, and the need to bring more a more life-like, immersive viewing experience is driving the transition. The digital age is the railroad track for this transition. Movies are created with a wider, more rectangular aspect ratio (16:9 or wider) in order to create a larger viewing surface and bring the viewer more into the film. On a traditional 4-by-3 aspect ratio display, these movies must be letterboxed (where the entire image is shown with black bars above and below it) or cut down in size (pan and scan where portions of the image are cut out and not displayed resulting in an image which fills the 4:3 screen but does not contain the entire movie image as seen in the theater).
Frequency – how many times each second a sound wave repeats. Audio frequencies are measured in Hertz (Hz) 1 cycle per second, or kiloHertz (kHz) 1000 cycles per second. The human ear can hear frequencies from approximately 20 Hz to 20,000 Hz (20 kHz).
Frequency response – the range in frequencies over which an audio component or system can produce a useable, fairly flat, undistorted output. Frequency response is usually specified as a frequency range with a +/- level deviation expressed in dB, such as 20 to 20,000 Hz ±3 dB. The speakers greatly limit the frequency response of most audio systems.
Front Projection / Front Throw Projector – Conventional projection technique of displaying an image on a white surface. The viewer and the projector are on the same side of the screen. The alternative is to rear project an image on a translucent screen where the viewer is on the opposite side of the screen from the projector.
Fullness – a subjective term used to describe sound. The fullness of a sound relates to the amplitude of the reverberant sound relative to the direct sound. Fullness corresponds to longer reverberation times, while clarity corresponds to shorter reverberation time. Fuller sounds are generally associated with romantic music or performances by larger groups, while clarity is desirable for speech.
Genius Loci – 1) An architectural vernacular described by Matthew Frederick in his book, “101 Things I Learned in Architectural School”, Genius Loci literally means genius of place. It is used to describe places that are deeply memorable for their architectural and experiential qualities. The Vietnam Veterans War Memorial in Washington, DC is such a place. 2) Answers.com – Latin term meaning ‘the genius of the place’, referring to the presiding deity or spirit. Every place has its own unique qualities, not only in terms of its physical makeup, but of how it is perceived, so it ought to be (but far too often is not) the responsibilities of the architect or landscape-designer to be sensitive to those unique qualities, to enhance them rather than to destroy them.
Grayscale (video) – is the range of gray at different intensities along a continuum with black on one end and white on the other end. Every color in-between is part of the grayscale. Interestingly, digital displays the grayscale as combinations of three (3) primary colors – red, green, and blue. In a nutshell, calibrating a video display for accurate grayscale helps ensure that black images are as close to black as possible and white images are as close to white as possible without the intrusion of unwanted colors. Our eyes are most sensitive to changes in the grayscale spectrum so slight differences in the grayscle rendering of a picture image will produce very noticeable, unwanted effects. When a ISF-certified calibrator adjusts the grayscale they target setting the entire range to the CIE standard of 6500K and a x/y coordinate of .313/.329. It is impossible for any video display to have its grayscale adjusted via the user controls or, for that matter, without expensive calibration equipment the ISF-certified calibrator has for this purpose. All displays benefit from grayscale adjustments and it is part of a suite of tests and adjustments performed by an ISF-certified technician. Most, if not all, video displays will require periodic adjustments to perform inside the dynamic range – clear, crisp and accurate grayscale with life-like, accurate colors in sharp, detailed resolution.
Ground Loop – 1) A state where too many electrical grounds are connected at different points. The earth potential path becomes unstable with varying potentials between different pieces of equipment. As the potential varies new circuit path loops are created. This usually causes an audible frequency (60Hz in the U.S.; plus harmonics) hum from the electronics to the speakers. 2) A potential system grounding problem that may produce symptoms that appear as sync noise and causes a horizontal bar to “roll” vertically on the video image. A ground loop occurs when some devices in a system are not connected to the same electrical ground. This can create a voltage potential between “ground” on the different pieces of equipment.
Haas Effect – the ability of the human auditory system to integrate late reflections that occur within about 5 to 50 milliseconds after the direct sound with the direct sound, and correctly localize the sound source. In most cases these reflections help to reinforce the direct sound and enhance the audible character of the sound. This effect is also referred to as the Precedence effect.
HDCP (High-Bandwidth Digital Content Protection).– Content owners in Hollywood stand behind this copy protection scheme to frustrate would-be pirates. Developed by chip-maker Intel, HDCP uses an authentication protocol to protect programs from being copied. The device on the transmitting end – an HDTV satellite receiver, for example – must first verify that the device on the receiving end is licensed to accept the copy-protected content. If it is, a “hardware handshake” occurs so the program can be tramsmitted.
HDMI (High-Definition Multimedia Interface) – is an evolved HDTV connection format using a DVI interface that transfers uncompressed digital video with HDCP copy protection and multichannel audio. In the quickening evolution of digital content protection (DCP) that Hollywood studios are looking for, electronic manufacturers will support, and friendly-enough for consumers – HDMI is a step in the right direction. 2) The www.hdmi.org website says HDMI is the first and only industry-supported, uncompressed, all-digital audio/video interface. Their claims that HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable have been substantiated. 3) HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel digital audio, with bandwidth to spare to accommodate future enhancements and requirements. 4) HDMI founding members include Sony, Philips, Hitachi, and Panasonic. It has the support of major motion picture studios including Fox, Universal, Warner Bros., and Disney. Intel is providing the High-bandwidth Digital Content Protection (HDCP) for HDMI.
Per www.hdmi.org – the 5 reasons to consider HDMI for home theater are:
- All-digital gives the highest quality available.
- A single cable connection means no more confusion, no more tangled cable mess.
- Integrated remote option provides simple setup and control of a HDMI-linked system.
- Automatic format adjustment of viewed content.
- Backward compatible to support DVI-equipped products.
HDTV (High Definition Television) – High definition TV is a television standard with higher resolution The 1,125-, 1,080- and 1,035-line and 720, and 1,080-line progressive formats in a 16:9 aspect ratio. Officially a format is high definition if it has at least twice the horizontal and vertical resolution of the standard signal being used. There is a debate as to whether 480-line progressive is also high definition. Most experts hold it is not more than a juiced-up NTSC (standard TV resolution) format but grudgingly give it an “enhanced definition format” distinction. The ATSC, the definitions body for high definition formats, has established 18 different formats that can be considered high definition. These formats each bring a different resolution for the consumer. The difference between a display with EDTV 480p60 resolution and HDTV’s 1080p resolution is striking. In this example the pixel real estate of EDTV is 307,200 and 1080p is 2,073,600 giving the 1080p display more than 600% the resolution of EDTV. The clarity of the 1080p HDTV picture would be analogous to viewing the same picture in HDTV from 10-feet and an EDTV display from 50-feet!
HDTV (True HD) – the majority of major studios and video industry players consider 1920 x 1080p as the de facto resolution for HD video disc content. In fact, these same studios are betting that consumer interest in displays for 1080p, and superior film viewing at home over other HD content delivery (ex. – pay TV and the Internet) represents an enormous market opportunity. Most major studios have the capabilities to master the HD content right now (2005). Many have already mastered their last 10 years’ libraries in HD.
Headroom – the ability of an amplifier to momentary produce more than its rated continuous average or RMS output power without distorting. Headroom (also called dynamic headroom) allows an amplifier to reproduce loud sounds like explosions. Headroom is expressed in dBs.
Helmholtz Resonators – are widely used to achieve adequate absorption at lower audio frequencies; a reactive, tuneable sound absorber. Boomy atmospheres in rooms (or the lack of them – i.e. room modes) significantly distract and subtract from a viewer’s viewing and listening experience 2) There is nothing particularly mysterious about such resonators. Blowing across the mouth of any bottle or jug produces a tone at its natural frequency of resonance. The air in the cavity is springy, and the mass of the air in the neck of the jug reacts with this springiness to form a resonating system, much as a weight on a spring vibrating at its natural period. Change the volume of the air cavity, or the length or diameter of the neck, and you change the frequency of resonance. The sound impinging on a Helmholtz resonator that is not absorbed is re-radiated. As the sound is re-radiated from the resonator opening, it tends to be radiated in a hemisphere. This means that unabsorbed energy is diffused, and diffusion of sound is a very desirable thing in a listening room. 3) Acoustical artifacts applied these Helmholtz principals. Resonators in the form of large pots were used in ancient times by the Greeks and Romans in their open-air theaters, apparently, to provide some reverberation in the non-reverberant outdoor setting. 4) The use of Helmholtz’s theories on sound wave energy is fundamental to the design and construction of “well-behaved” rooms and spaces for viewing films, listening to music, and playing interactive games. 
Hertz (Hz) – a measure of frequency in cycles per second. The frequency of waveform in Hz is equal to the reciprocal of the time for one cycle (f=1/T). One hertz equals one cycle per second. Human hearing ranges from approximately 20 Hz to 20,000 Hz (20 kilohertz).
Holodeck – In the Star Trek fictional universe, the holodeck is a virtual reality facility, generally on starships and star bases. Theorized by Janet Murray as a potential immersive environment in which cyber dramas are enacted. Integral to this procedural, participatory, immersive, and encyclopedic environment is the computer.
Home Acoustics Alliance (HAA) – is an alliance of independent audio/video professionals dedicated to the pursuit of sonic greatness in the home entertainment experience. The HAA has been working over the years to create a worldwide network of expert audio calibration practitioners. Their mandate is divided equally between creating superb home audio and educating the consumer. The HAA believes consumer awareness drives the evolution of excellence. An HAA professional stands out by defining excellence by releasing the calibration of sound system performance from the realm of uncertainty to become a disciplined art and science Understandably, it is easy to see that most consumers depend too much on the quality of their audio equipment to provide high end results without regard for the proper set-up and calibration. The Home Acoustics Alliance has a mission; it is to make every audio buyer aware that proper setup and calibration of audio equipment is essential for good results. This is true despite the perception enabled by many factions in our A/V industry that says the best way to solve a sound problem is to buy more expensive equipment. The HAA alliance of Dealers, Manufacturers, and Consumers teach the science of good sound and to bring it home to their clients. The Home Acoustics Alliance website is located at http://www.homeacoustics.net.
Home Theater – is a term to describe a complete audio/video system consisting of a video display, at least one video source, and a full surround sound system (Dolby Pro Logic, Dolby Digital, or DTS). A home theater allows you to experience movies in your home with the same or greater feeling of involvement and action than you do at a commercial movie theatre. 2) also described as “a space dedicated to the faithful reproduction of film.”
Hum – continuous, undesired low frequency audio noise. Hum is usually caused by 60Hz electrical interference. Hum may also occur at the 2nd harmonic, or 120 Hz. Hum is the result of a poor or broken audio cable, a loose or dirty connection, or a power supply problem in an active audio component. In audio, a “hum” can be heard; in video, waves in the picture.
Imaging – is the ability to reproduce localized sounds that appear to come from different, specific locations. An audio system that has good imaging creates a three-dimensional sound environment that seems to have depth, width and height. Good imaging allows listeners to determine where an instrument, voice or other sound source is located on the live performance stage, as if they were actually there.
Immersive – one way of describing immersive is the feeling you have participating in an experience that allows you to freely release yourself to become part of that experience. It comes, in part, because of your willingness to focus your thoughts and open up your senses to “take in” the experience. Deeper philosophical discussions surround the question “what is real?” To have a “real” experience is to allow your attention -a combination of your mind, senses, and spiritual self to receive cues for your manifesting a physical reality in present time. 2) Wikipedia.org describes immersive digital environments as synonymous with virtual reality, but without the implication that actual “reality” is being simulated. 3) We believe what you experience “is” your reality. It’s you, the participant, becoming part of the experience with your perception shaping your perspective. If this experience is real enough for you there is a suspension of disbelief for an undetermined period of time. 4) There are many factors shaping immersive experiences. Our efforts as architects of Immersive RealismTM experiences is all about attaining a level of command over these factors to shape peak experiences involving what you see, hear, feel, and interact with while watching movies, listening to music, and playing interactive games.
Immersive RealismTM is the peak experience gained by the viewer, listener, or interactive gamer from a room environment designed, built, and tuned to envelop you in that experience – where “perception is your reality.” Immersive Realism is created by effectively harnessing and tuning the convergence of these elements – 1) acoustics, 2) picture acuity, and 3) architectural design and aesthetic presentation in the room/spaces selected for A/V/G (i.e. – Audio, Video, and Gaming) entertainment. To experience Immersive Realism is not an all-or-nothing reality. Rather, it is the cumulative, balanced coming together of sensory cues conducive to creating the depth and breath of immersive experience. Thus, the more attention given in planning, building, and convergence tuning of these elements the more unified, cooperating these elements become to support peak experiences. Immersive Realism is then appropriately described as a dimensional range of possibilities that can be harnessed for the viewer in the environment they wish to be participants in. Immersive Realism is often expressed by those experiencing it as being transported or placed in the experience. That experience finds itself inside “The Magic Quadrant” of possibilities. The Holy Grail, the ultimate peak experience, has yet to be achieved. It would be reminiscent of the totally immersive, interactive virtual reality experience found in the holodeck of Star Trek’s fictional universe.
Interconnects – Any cable or wire running between two pieces of A/V equipment. For example, a fiber-optic cable connects digital optical audio sources to a A/V receiver, and RCA terminated cables connecting pre/pros and amps.
ISF (Imaging Science Foundation) – is an organization of video professionals founded in 1994 by Joel Silver and Joe Kane dedicated to increasing the quality of video displays in the home and how images are presented on them. The ISF works with consumer electronics manufacturers in product development, and trains and certifies dealers to deliver superior film and entertainment display images that are not possible straight out of retail store and the manufacturer’s shipping box. They bring out the real picture inside a client’s display. With the growth of high definition TV and home theater the need for calibrating the video display is even greater to get consumers to the next level of image quality. The vast majority of ISF dealers are electronics specialists who feature video calibration, audio calibration and system automation with their installations. The ISF website is at http://www.imagingscience.com.
Late Reflections – is reflected sound that arrives at the listener more than 50 milliseconds after the direct signal. If they are not too late or too strong, late reflections add fullness to sounds. Late reflections create an effect called reverberation. See early reflections.
LCD (Liquid Crystal Display) – is a device that displays text and graphics on a flat screen that uses no projected light or illumination. As a display device it is particularly suited for laptops, and computer displays reach 21-inches in diameter and more. Unlike plasma displays that can draw 700 watts and more for 50-inch displays a LCD draws very small amounts of power making it suitable for battery powered devices. The drawbacks of LCDs are difficulties with multiple video resolutions, external light or ambient light in the viewing area, and a reduced viewing angle. Sony has invested in LCD technology for home theater and has made progress in increasing the viewing angle (i.e. to the left and right of center screen viewing) of their displays and in brightness control. Today (2005) a LCD display can be as large as 80-inches diagonally.
LCD PANEL – is a device used to project video images through a Liquid Crystal Display and an overhead projector onto a large screen.
Letterbox – is a way to display widescreen material on a non-widescreen display retaining the full width of the film’s original aspect ratio with placing black bars above and below the image to fill the unused screen space. An advantage of the letterbox is maintaining the film’s original cinema aspect ratio to see everything the director intended you to see. Some disadvantages of the letterbox are the shrinking of the viewing area of the TV screen and the loss of some horizontal resolution. Keep in mind that the letterbox is used with TV displays not capable of presenting widescreen material.
LFE (Low Frequency Effects) – an audio channel on Dolby Digital and DTS 5.1 audio surround sound formats that contain low bass frequencies from 3 Hz – 120 Hz. Because the frequency range of the LFE channel is approximately one-tenth the bandwidth of the other channels, it is known as the “.1” channel. The LFE channel is an optional channel that is used in some movie soundtracks to provide extra bass punch for explosions, rumbles, etc. so the listener can feel the sound.
Localization – is the ability to determine the location of a sound source. We localize sound based on two primary cues: 1) the ear that is closer to the sound source hears a slightly louder sound (more of a clue for higher frequency sounds) and, 2) sound reaches the ear that is closer to the source slightly before it reaches the other ear (more of a clue for low-frequency sounds). Another, lesser clue is how frequencies are accentuated or attenuated by minute time delays caused by the folds and depressions in the listener’s ear. Localization is most precise for sound sources that are located in front of the listener and at ear level. Localization involves the whole brain and is not just a function of the ears.
Loudspeaker – another term for speaker. A speaker refers to the whole package of drivers, enclosure crossover network and connectors, although it is sometime used in place of speaker driver to mean a component that converts electrical energy into sound.
Luminance – 1) Brightness; the black and white component of a video signal. The amount of luminance is directly related to light intensity or brightness. 2) The black and white (Y) portion of a composite, Y/C, or Y/Pb/Pr video signal. The luminance channel carries the detail of a video signal. The color channel is laid on top of the luminance signal when creating a picture. Having a separate luminance channel ensures compatibility with black-and-white televisions.
LUX – Refers to the amount of light per square meter incident on a surface. 1) lux = 1 lumen/square meter = 0.093 foot-candles. 2)a metric unit of measurement of the quantity of light output hitting a surface. Is calculated by measuring the measuring the candela and multiplying by the area of the projection screen. 3) a Ten lux equals approximately one foot-candle. See ANSI and Brightness (peak).
Magic Layout – refers to an optimum location of A/V system loudspeakers, subwoofers and video display relative to the placement of the primary seats which the unique sonic characteristics of the room environment affords. The choice of optimum and alternate layouts for a room providing theater, listening and/or interactive gaming experiences is the result of disciplined and creative data gathering, analysis, testing, and tuning by an A/V convergence tuning specialist. These specialists, such as the sight & sound lifestyle architects of Hi-Definition Living, know the procedures, the best practices, and the secrets to delivering Immersive RealismTM peak experiences for their clients.
Motion Artifacts – in all temporally-sampled systems (i.e., both photographic and electronic), realistic motion reproduction is achieved only with sampling below the Nyquist limit. The subjective response to motion artifacts is complex, influenced by the various degrees of smoothing and strobing affecting temporal and spatial resolution – integration and tag in the sensing, recording, and display elements; sampling geometry and scanning pattern; shutter transmission ratio; perceptual tolerances, etc. (Motion appears “normal” only when significant frame-to-frame displacement occurs at less than half the frame rate; i.e., “significant motion” distributed over at least two frames.) Motion artifacts most frequently observed have their origins in the following: (1) image components with velocity functions extending beyond the Nyquist limit (such as rotating, spoked wheels), (2) motion samples with such short exposures there is noticeable frame-to-frame separation of sharply defined images (such as synchronized flash illumination). (3) asynchronous sampling of intermittent motion (such as frame-rate conversions). A considerable number of motion artifacts appear so frequently as to be accepted by most viewers..
Noise – is any unwanted sound or interference, including sounds like hiss, hum, whine, static, or buzzing. Noise may be caused by electronic components, or it may be caused by interference from outside signals. Noise that is a random waveform containing all audible frequencies is called white noise. Noise that contains all frequencies with equal energy per octave is called pink noise. Pink noise and white noise are commonly used to make sound measurements. A noise signal that is filtered to remove the higher and lower frequencies is called narrow-band noise. Filtering out the high frequencies produces low-pass noise.
Noise Criteria (NC) – is the number rating of the background noise level in a room. The NC number corresponds to energy level-versus-frequency curves called Noise Criterion curves. It is important to have very low background noise (ideally less than NC20) in a Home Theater since the background noise directly affects the dynamic range of the audio. If the noise level is too high you will need to turn up the system to hear the quietest passages; however this makes the loudest passages even louder. To determine the NC rating of a room, octave-band frequency noise levels are measured and plotted against the series of Noise criteria (NC) curves.
Noise Criteria Curves (NC) – is a set of standardized, subjective equal loudness curves used to rate the background noise of indoor environments. The Noise Criteria curves specify the maximum allowable level of noise in 8 octave bands over the entire audio spectrum. These curves take into account the predominant frequencies and sound pressure levels where the ear is most sensitive. The lower the NC rating, the less background noise. Peak performing home theaters should have an NC rating below NC20.
Parametric Equalizer – is a type of equalizer that allows the gain, center frequency and bandwidth to be adjusted for a desired band of frequencies. Unlike a graphic equalizer that only provides adjustable gain for preset frequencies, parametric equalizers provide adjustments for only a few frequencies, but these adjustments can be made at any desired frequency and bandwidth. Parametric equalizers that use rotary controls are called quasiparametric. Parametric equalizers that use slide controls are called paragraphic.
Phase – 1) specific point in a cycle referenced to the starting point or zero point reference, or 2) the time relationship between two signals. Phase is commonly expressed as an angle of a sine wave, with one complete cycle representing 360 degrees. A 180-degree phase shift corresponds to inverting a waveform, regardless of its shape. Two identical signals that are shifted 180 degrees are called out of phase, and the signals totally cancel. Phase is also identified in terms of time. Two identical waveforms are in phase if a corresponding point (such as the positive peak) on both arrives at the same time. If they are not in phase the time difference between the two points is the phase difference in seconds. Speaker drivers are in phase when the diaphragms are moving in and out at the same time. When speaker drivers are in phase they provide better bass response and proper stereo imaging.
Picture Contrast (Video) – One of the 6 key elements supporting peak performance in video displays is the difference between the peak white and maximum black a video display can produce. 2) The human eye perceives a higher contrast ratio as a brighter, not necessarily better, picture. Our eyes are most sensitive to changes in black levels (the gray balance). Black levels have more affect on contrast than white levels. A less-than peak performing video display will have problems producing black in night scenes and in scenes where anything less than a daytime, outside scene is viewed. A scene of your favorite actor or actress inside a less-than-bright room with their hair appearing more helmet-like than showing strands of hair is having problems with gray balance and contrast. These so-called problems could also be related to the ambient light existing in the room where viewing takes place. As a result, peak performing video displays must take into account the characteristics of the room whether during the day or the night.
Picture Geometry – One of the 6 key elements supporting peak performance in video displays, picture geometry are shape distortions typical of out-of-balance alignment, accuracy and focus with a display’s rendering mechanics. Causes of geometry issues include a lack of picture centering, size, convergence, and linearity. Their effects include shape distortions, visual angles (i.e. image size and proportions), and color spotting. 2) As the popularity of rear projection systems grow so, too, do the issues with picture geometry. They are most prevalent on these systems. It’s not a defect, it is a feature of a technology where the video picture is projected onto another surface. All display technologies can illustrate picture geometry distortions. 3) Convergence is precisely overlaying red, green, and blue images at all points on the video display.
Picture Uniformity – One of the 6 key elements supporting peak performance in video displays relates to its ability to reproduce the chromaticity (color hues and saturation) and luminance (black and white) of the video signal. 2) The light output is often not consistent across across a video display screen. This is a lack of uniformity. Many displays and the technologies (CRT, Plasma, LCD, DLP, …) driving the displays may produce light fall-off of as much as 50% from the center to the edge of the picture, and not be noticed by the human eye. Generally, the less the light output level the better. 3) As light output from a video display changes over the luminance (light) range, the color of the gray background should, ideally, remain perfectly constant, at the desired white reference (ISF calibrators call this “white balance”). A color variance of 20 delta E or less from the desired white reference color yields visually acceptable results. An ISF-certified calibrator will work to bring a delta E measurment as close to 1 as possible given the electronics of the client’s video display. The lower the delta E the better.
Pink Noise – is random noise signal that has equal energy per octave bandwidth (each octave band has the same average power). Pink noise is a common test tone that is used to adjust equalizers and audio systems for a flat frequency response. Pink noise does not sound a bright as White noise because the intensity of the spectrum does not increase at higher frequencies. White noise has equal energy for all frequencies, and is another common test signal. Pink noise is created by passing white noise through a filter having a 3 dB/octave roll-off rate.
Pitch – is the frequency of a tone. Two aspects of the notion of pitch can be distinguished in music: one related to the frequency (or fundamental frequency) of a sound (measured in Hz) which is called pitch height, and the other related to its place in a musical scale which is called pitch chroma. Pitch height varies directly with frequency over the range of audible frequencies. This “dimension” of pitch corresponds to the sensation of “high” and “low.” Pitch chroma, on the other hand, embodies the perceptual phenomenon of octave equivalence, by which two sounds separated by an octave (and thus relatively distant in terms of pitch height) are nonetheless perceived as being somehow equivalent. This equivalence is demonstrated by the fact that almost all scale systems in the world in which the notes are named assign the same names to notes that are roughly separated by an octave, i.e., the labeling system cycles at every octave. Thus pitch chroma is organized in a circular fashion, with octave-equivalent pitches considered to have the same chroma. Chroma perception is limited to the frequency range of musical pitch (50-4000Hz).
Pixel – 1) Originally an acronym for picture element. Now increasingly restricted to defining the digitized sampling of images. 2) a pixel is the digital representation of the smallest area of a television picture capable of being delineated by the bit stream; i.e., the digital value or set of values that defines the characteristics of a picture element. A pixel of a full color image is represented by a minimum of three components, reflecting the trichromatic nature of human vision. A pixel of a monochrome image may be represented by a single component. 3) pixels may carry additional information such as transparency, etc. 4) the total number of picture elements in a complete picture is of interest since this number provides a convenient way of comparing systems.”
Picture Element – a pixel is the smallest display element on a video display screen. A screen is broken into thousands of tiny dots, and a pixel is one or more dots that are treated as a unit. A pixel can be one dot on a monochrome screen, three dots (red, green and blue) on color screens, or clusters of these dots.
Picture Resolution (Video) – One of the 6 key elements supporting peak performance in video displays. Ultimately, a video display’s ability to produce high quality images is related to 1) the pixel count of a display device or a source ( i.e the lowest common denominator) and 2) the calibration of black level, white balance, and user controls by an ISF-certified calibrator to the client’s viewing environment at home. 2) A video display’s native resolution is referenced by the number of horizontal lines multiplied by the number of vertical lines that it is designed electronically to reproduce. Every high-definition video display has a maximum resolution (number of pixels = V-lines x H-lines). A 1080i HD display is capable of producing an image with 1080 vertical lines and 1920 horizontal lines. The total pixel count of this particular display is 2,073,600 – the highest available to consumers today. 3) Whether or not any display will reproduce quality images depends on the source of the image, the quality of electronics reproducing the image, and whether the image and electronics have been optimized by an ISF-certified calibrator for the client’s environment and intended uses. 4) The quality of resolution that a client perceives depends on the video display’s abilities over 3 dimensions – depth, textures, and realism. The more you can harness the better the viewing experience.
Plasma Display – a plasma display is an emissive flat panel display where light is created by phosphors excited by a plasma discharge between two flat panels of glass. The gas discharge contains no mercury (contrary to the backlights of an AMLCD); a mixture of noble gases (neon and xenon) is used instead. This gas mixture is inert and entirely non-harmful. 2) The Plasma display panel was invented at the University of Illinois by Donald L. Bitzer and H. Gene Slottow in 1964 for the PLATO Computer System. Enjoying commercial popularity in the 1970s as a B/W display until advances in semiconductors made CRT displays a incredibly cheaper alternative. Blitzer and Slottow invented the Color Plasma display in 1995 with brightness and viewing angle advantages over other display technologies. 3) These displays are dependable with upwards of 60,000 hours operation and half-life (i.e. half of its original brightness and intensity) when displaying video. A downside of a plasma display is susceptibility to burn-in where a video image remains imprinted on the display screen (See Plasma Display “Burn-in”). 4) Today’s (2005) plasma displays can be as large as 62-inches diagonally and growing. The depth (i.e. side view) of 62-inch display can be 6-inches or less unlike LCD technology that, while getting more narrow generation-to-generation, is in the range of 20-inches in depth.
Plasma Display (Burn-in) – for your typical TV content this will probably never be an issue. However, if you watch particular content where a video image stays locked on the display screen for hours at a time, say on a news, investment (e.g. – Bloomberg) or sports channel, or if you play video games a lot – it’s safer to avoid plasma. The ticker tape or game controls remaining stationary on the screen can permanently “burn-in” to the plasma screen’s phosphor coating leaving a faint image. So, the two primary ways to avoid burn-in are to avoid fixed images (ex. Photos, gaming, new and sports services…) and having the display calibrated to balanced black and white levels by an ISF-certified professional. An ISF calibration will increase the “wow” viewability of any display and help extend the useful life of your plasma display.
Proscenium – an architectural feature common to theaters. A proscenium is that part of the stage between the curtain and the orchestra pit. The architectural arch which encloses the curtain is called the proscenium arch. Proscenium is also used in a more general sense in the meaning of a stage constructed with a curtain as opposed to a thrust stage where the stage is out in the open without a formal enclosure.
Psychoacoustics – the study of the complex reactions of the listener to surrounding sounds.
Rear-Projection Displays (a.k.a. RPTV) – are displays where the picture is projected onto the rear of a translucent screen via a series of mirrors toward the audience. The mirrors are used to direct and correct the picture image. This display technology has been around for years known as CRT-based (tube-based) RPTVs. A new generation of RPTVs are available – microdisplays. They essentially consist of a lamp that bounces light off of or through a tiny pixel-filled microchip and onto a big screen. The three (3) most prevalent microdisplay technologies today are built on DLP, LCD, and LCoS and its variants. The more noteable characteristics of microdisplay RPTVs are:
- Unlike rear-projection CRT sets, all microdisplays are bright light engines. DLP and LCD produce very good black
levels so they’re more watchable in brightly lit rooms.
- The TVs are generally lighter and slimmer than CRTs, and generally are placed on a stand to be at eye level.
- The lamps inside these sets, which cost $200 and up, must be replaced every 3,000 to 10,000 hours, depending
on the technology and conditions of use. Most lamp assemblies are user-replaceable.
Reflection – is a sound wave that changes direction. When a sound wave strikes an object that has larger dimensions than the sound’s wavelength, the object reflects the sound much like a mirror reflects light. All reflected sounds either help to reinforce the direct (or non reflected sound) or they cancel and distort the direct sound. 2) Each and every room has its own unique acoustic character. Left acoustically untreated, rooms will create unwanted sound effects that can distract or remove the prospects of ever reproducing the experience that a film director, the music conductor, and games developer intended. An acoustic specialist knows how to identify the sound waves to encourage, those you want less of, and those that you want to remove altogether. Strong, early reflections can distort the intended sound source (bad) and destabilize the realism of a three-dimensional sound stage. Reflections that repeat many times between parallel surfaces (i.e. slap echoes) are undesirable, too. Acoustic specialists identifies the good and bad reflections created by the room’s design and surface materials, and introduces the needed corrections to bring sonic balance back into the room.
Resolution – 1) a measure of the finest detail that can be seen, or resolved, in a reproduced image. While influenced by the number of pixels in an image (for high definition the resolution of 1, 920 x 1,080 is currently available through consumer electronics channels (2005). The most prevalent standard still is NTSC which is found in today’s basic television set (TV) which has a broadcast resolution not exceeding 720 x 487 pixels, and commonly 520 x 480. Pixel numbers do not define the ultimate resolution but merely the resolution of that part of the equipment. 2) the quality of lenses, display tubes, film process and film scanners, etc. Used to produce the image on the screen must all be taken into account. This is why a live broadcast of the Super Bowl presented in HD format looks better than the same broadcast recorded and played from VCR, Tivo, or even a DVR. Why? Because these recording devices have a lower resolution for recording and so you get that resolution on playback.
Response – is one of the five (5) sonic goals of any theater system as described by HAA (Home Acoustics Association). Response is a system’s frequency response is a measurement of the relative levels of all the reproduced audio frequencies. The response’s smoothness can be observed in a variety of ways – as improper tonal balance, including boomy bass, excessive treble, improper musical timbre, or a general lack of realism. Factors of importance include selection of high-quality components and proper system setup, including (in a small room) proper listening and speaker positions and correct use of equalization. At a minimum, the system must be non-fatiquing at all sound levels, articulate, and faithful to the original signal.
Reverberation – the sound that momentarily persists in a room after the initial sound is removed. The length of time it takes for this sound to decay to an inaudible level is called reverberation time. Reverberation is caused by multiple reflections of sound waves bouncing off the room’s walls, ceiling and floor, as well as other objects within the room. Reverberation is increased by hard surfaces, such as wood floors and paneled walls, and is decreased by absorbing materials such as rugs, carpet and drapes.
Room Interaction – how a room affects the quality of reproduced sound. Room interaction creates the characteristic acoustics of a room. The walls, floors and ceilings create reflections that either reinforce or cancel each other. Room interaction colors or distorts the sound. Hard surfaces increase reflections and make a room “live” while absorbing surfaces make a room sound dead. Low bass frequencies are especially prone to room interaction because of their long wavelengths. Low frequency room resonance causes loud and boomy sounds at the frequencies where the standing waves reinforce.
Room modes – are the areas of high and low sound pressure inside a room that are caused by the reinforcing and canceling of multiple sound waves at room resonance. Room modes are often called standing waves, and occur at the resonant frequencies of the room. The strength of a room mode changes with location within the room. A room mode that results from two reflective surfaces is called an axial mode.
Saturation – the intensity of the color is called saturation. For example, a lightly saturated red looks pink. Fully saturated red is like the red of a crayon. On a display device, it can be adjusted with the Color control. Not to be confused with the brightness, saturation is the amount of pigment in a color, and not the intensity. Low saturation is like adding white to the color.
16:9 (Sixteen Nine) – the widescreen aspect ratio used for displaying video. The displayed image is 16 units wide (horizontal measure) by 9 units tall (vertical measure) creating a rectangular effect similar to the screen at a movie theater. It is a compromise aspect ratio situated between the nearly square 4-by-3 ratio of most current television sets and the often wider ratio used for many movies. The 16-by-9 ratio was determined to provide the best compromise eliminating the black bars for letterbox format movies (or decreasing them to thin lines for movies filmed in a wider aspect ratio) while minimizing the bars required for traditional television material recorded in the 4-by-3 ratio. 2 The 16:9 aspect ratio is the new ATSC standard to be used for digital television broadcasts. As we transition from the NTSC analog standard to the digital age the 16:9 aspect ratio will become standard. TV displays are becoming wider and narrower to show movies and more movie-like content.
Sound Pressure Level (SPL) – the ratio of the pressure, or force, created by a sound wave compared to the threshold of hearing pressure (20 uPa). Sound pressure level is expressed in dB SPL, but the SPL is usually assumed. SPL corresponds to the perceived loudness or volume of a sound. Higher sound pressure levels produce louder sounds since they create more pressure in the ear. A 10db increase in SPL is perceived as an approximate doubling in volume. The smallest change in sound pressure level that the ear can detect is 1dB. Sounds become quieter as we move farther from the source. Each doubling in distance from a sound source results in -6 dB change in sound pressure. Sound pressure level is measured with an SPL meter. Some examples of sound pressure levels are: whisper – 20 dB; normal speech – 70 dB; passing subway train – 100 dB; large jet plane – 120 dB. Live orchestral music reaches brief peaks in the 105db range and live rock easily goes over 120db. 140 dB SPL can cause irreparable hearing damage, 150 dB SPL can cause instant deafness, anything greater than about 192 dB SPL can kill you.
Sound Stage – 1) a room or studio that is usually soundproof, used for the production of movies. 2) the psycho acoustic phenomena where a two-dimensional image (left-to-right and front-to-back) is created in the mind suggesting the physical relationship of the listener to the individual performers. A well designed listening space will create the impression of a much larger sound stage than the physical placement of the speakers or the size of the room could allow. 3) a reproduced soundstage should ideally duplicate the original performance and have proportional width, depth and height, making it sound as if you were at an actual performance.
Sound Wave – an audio frequency waveform that travels though air by creating areas of lower and higher air pressure. Sound waves have wavelengths that vary greatly, ranging in length from approximately 56 feet at 20 Hz to just 2/3 of an inch at 20 kHz. Louder sounds create larger pressure differences, and higher frequencies create pressure changes that occur more rapidly. High-volume, low frequency sounds create massive sound waves that can be heard and physically felt.
Subwoofer – speaker that reproduces only the very low bass frequencies below about 80 Hz. True subwoofers can reproduce frequencies of 20Hz or even lower. A subwoofer is used along with a woofer to reproduce the whole range of bass frequencies below about 500 Hz. If just one speaker is used to reproduce the bass frequencies, the speaker is called a woofer. The low-frequency effects (LFE) channel is designed specifically for subwoofers. Subwoofers can be powered or non-powered. Powered subwoofers have a built-in amplifier, while non-powered subwoofers require an external amplifier. Powered subwoofers are the most common.
Sweet Spot – the prime, or best listening position. An audio system set up to produce optimal sound in the sweet spot. Ideally, the sweet spot should be large enough to include every listener, but this is often not possible. The sweet spot is usually located at a point that is about halfway between the front speakers and back about the same distance.
Symmetrical Room Design – a basic acoustical design to create a desirable listening environment. Draw a line through the center of the room, the left side should be a mirror image of the right. Should the boundaries of a room be asymmetrical, sounds heard by one ear will receive one combination of direct and reflected sound, while the other ear will hear a different balance.
THX (THX Ltd.) – provides technologies and services for optimizing the production and playback of entertainment content in the professional and consumer markets. The company’s certification programs and technologies deliver the ultimate entertainment experience, providing superior playback of movies, music and games, and improving the interoperability of entertainment products and applications. Today, thousands of commercial cinemas, post-production studios, home entertainment products, DVDs and games have been designed and certified by THX. THX-certified theatres use professional Dolby cinema processors for playing Dolby soundtracks (which is why both logos can appear on the same theatre marquees). For home theaters THX has a network of trained technicians who design, install, and calibrate to specifications delivering cinema experiences that film directors intended for their audiences. THX, founded in 1983 by film director and industry thought leader George Lucas, is headquartered in San Rafael, California. THX today remains a pioneer in entertainment technology by delivering unparalleled innovation and quality from the post-production, distribution and playback environments. The THX website is at www.thx.com and LucasFilm is at www.lucasfilm.com.
Timbre – quality of a sound that allows you to distinguish it from other sounds that have the same volume and frequency. The difference in sound between a trumpet and a saxophone playing the same note is timbre. Speakers have different timbres, so speakers that are used together such as the front left, right and center speakers should all have similar timbre.
Wavelength – the length of a sound wave in air. Wavelength (l) is equal to the speed of sound in air (1130 feet/second @ 20°C) divided by the frequency of the sound (l= 1130/f). The wavelengths of audio waveforms range from about 56.5 feet at 20 Hz, to 0.057 feet (0.68 inch) at 20 kHz. This is one reason why subwoofers are so large and tweeters are so small, and why low audio frequencies cause room mode problems.
Weber’s law – discovered by Ernest Heinrich Weber in 1834. Weber’s Law states that the smallest detectable change in intensity is a constant fraction of the level of stimulation. Georg Fechner turned Weber’s law into a psychophysical logarithm of the magnitude of stimulation (I), or S = k log I. A great deal of psychophysical research has attempted to establish the Weber-Fechner law for sensory dimensions other than intensity, e.g., frequency and duration in audition. While the empirical data conform fairly well to the law over a certain range of values for each dimension, they can differ substantially at extremes of the range of perceptible values.
Widescreen – is a term given to picture displays that have a wider aspect ratio than standard NTSC TV’s 4:3 aspect ratio. Widescreen typically identifies the 16:9 aspect ratio of HDTV but is also referenced to other formats indicated by the ATSC as “HDTV” or “HDTV-Ready”.