I have started writing a new series on the science behind music in “Saamagaana – The First Melody“, a monthly magazine on Indian Classical Music. The intent is to help readers understand a bit more about the science behind music and musical instruments and to enhance their appreciation of the same.
The article written for the April 2015 issue of the magazine is reproduced below. Please contact the magazine for subscriptions.
What is music, what is noise
What is music? How is bird song different from the mellifluous flow of the Mohana raga, the pentatonic scale common to so many cultures around the world? Why is one man’s beat another man’s poison? We begin a new series on the physics of sound and how our brain perceives music, voices and musical instruments, with R RAMKUMAR
Let us start with the basics. What is sound? How did you know that your wife just started singing in the kitchen?
When we throw a stone into a pool of water, it creates ripples that travel away from the place where the stone hits the water surface. In the same manner, when your wife makes a sound by singing, it creates ripples in the air that move away from her. This creates changes in the pressure of air which pushes your eardrums in and out when it reaches your ears. Your brain analyzes this and realizes your wife just started crooning.
How do you know what is music and what is noise? What is the difference between a musical note and noise?
When ripple patterns created by any sound reaches your ear, your brain can identify whether it is made up of repeating or non-repeating patterns.
Any musical sound or note, like the one’s made by your neighbor when she starts singing, is made up of a ripple pattern that repeats itself again and again. Any noise, like the one created when your neighbor slams her window shut to prevent you from hearing her practice, produces complex ripple patterns that don’t repeat. You come to know that it is noise because there is no regularity from which you can identify a musical tone.
A musical note consists of pitch, loudness, duration and timbre. We will try to understand each of these as we go along.
Why does a violin sound different from a flute?
The distinctive sound that each instrument produces is called its timbre. The same is true of human voice as well.
Violins have strings. When the violinist tries to play a note, the string starts to vibrate in many ways at the same time in a sort of a complex dance. The number of times anything vibrates per second is called its frequency. Since the string vibrates in many ways, it produces leads to multiple frequencies getting produced (called overtones) but the whole pattern of dance usually repeats at the same rate as the lowest frequency called the fundamental frequency. All other frequencies join to support this fundamental and produce a richer sound. Thus the quality of sound produced depends on the combination of different frequencies that go into its production.
When a flautist tries to play the same note, a different proportion of the various frequencies add to produce the note, creating a distinctive sound for the note that comes from the flute.
Thus, the same musical note sounds different when played on a violin and when played on a flute.
Why is, say, Sanjay Subrahmanyan’s voice different from Sudha Raghunathan’s?
As we saw in the answer to the previous question, the number of times anything vibrates per second is called its frequency. A close proxy of frequency is pitch. The more rapid the vibrations, the higher the pitch.
Human voice is produced due to vibrations of the vocal folds (vocal cords) created by air moving out from the lungs, upwards into the throat. An adult male usually has thicker/longer vocal folds than an adult woman which means that his vocal folds will vibrate lesser number of times per second. Hence his pitch will usually be lower. He usually has a larger vocal tract as well and his voice is lower and deeper. This is one of the primary differences between a male and a female voice and helps you decipher whether it is a male or a female singing.
Other factors include how sounds get habitually formed and articulated in an individual, which part of the body is being used to resonate the sound etc.
Piece all this together and you know whether it is Sanjay or Sudha.