<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>jerf</author><text>It&amp;#x27;s actually off-the-shelf tech now. I&amp;#x27;ve been in a number of supermarkets where they use this to beam ads at you while standing in line for the checkout. (All of which have since stopped doing it, for what it&amp;#x27;s worth. YMMV.)&lt;p&gt;There was some hope for a while that this might turn out to be a way to hack sound so that you could produce a flat speaker full of those tiny ultrasonic speakers, and then use non-linear interference to produce deep, booming bass sounds, without having to have the much-larger speakers you need today for that to work correctly. Unfortunately, either nobody could crack the technique, or it&amp;#x27;s simply impossible, because the real speakers that emerged are quite tinny. Here&amp;#x27;s a commercial offering, where they&amp;#x27;re only willing to promise down to 150Hz in the text: &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;ultrasonic-audio.com&amp;#x2F;acouspade-technical-specification&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;ultrasonic-audio.com&amp;#x2F;acouspade-technical-specificatio...&lt;/a&gt; &amp;quot;The sound is of high-quality, with low noise and great frequency response, which includes authentic reproduction of bass notes and frequencies as low as 150 Hz.&amp;quot; Which, if accurate, is better than the speakers I&amp;#x27;ve heard, but still a long ways from &amp;quot;thumping bass&amp;quot; coming out of a square that could be hung on the wall as casually as a picture frame.</text><parent_chain><item><author>weinzierl</author><text>&amp;gt; Yan was even able to embed an ultrasonic version of the Rick Astley song “Never Gonna Give You Up,” which became audible at the point where the two signals crossed.&lt;p&gt;At 33C3 I rode an escalator when I suddenly heard &amp;quot;Never Gonna Give You Up&amp;quot; but apparently no one else did. It was over after a few seconds. At the top of escalator there was a guy pointing a directional speaker at random people.&lt;p&gt;Only reference I could find is in German, but it has a picture [1].
The story says the guy on the picture is not the inventor of the device.&lt;p&gt;EDIT: The thing is a parametric ultrasonic speaker and the design files and software are on GitHub [2].&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;motherboard.vice.com&amp;#x2F;de&amp;#x2F;article&amp;#x2F;784z74&amp;#x2F;33c3--hacker-zeigen-ihre-gadgets&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;motherboard.vice.com&amp;#x2F;de&amp;#x2F;article&amp;#x2F;784z74&amp;#x2F;33c3--hacker-...&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;niklasfauth&amp;#x2F;parametricspeaker&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;niklasfauth&amp;#x2F;parametricspeaker&lt;/a&gt;</text></item></parent_chain></comment><story><title>&quot;Sonic attack&quot; may have been two ultrasonic signals accidentally interfering</title><url>https://spectrum.ieee.org/semiconductors/devices/finally-a-likely-explanation-for-the-sonic-weapon-used-at-the-us-embassy-in-cuba</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>ashleyn</author><text>I remember reading about this in &lt;i&gt;Popular Science&lt;/i&gt; when I was eleven years old. They compared it to the difference between laser light and conventional light.</text><parent_chain><item><author>weinzierl</author><text>&amp;gt; Yan was even able to embed an ultrasonic version of the Rick Astley song “Never Gonna Give You Up,” which became audible at the point where the two signals crossed.&lt;p&gt;At 33C3 I rode an escalator when I suddenly heard &amp;quot;Never Gonna Give You Up&amp;quot; but apparently no one else did. It was over after a few seconds. At the top of escalator there was a guy pointing a directional speaker at random people.&lt;p&gt;Only reference I could find is in German, but it has a picture [1].
The story says the guy on the picture is not the inventor of the device.&lt;p&gt;EDIT: The thing is a parametric ultrasonic speaker and the design files and software are on GitHub [2].&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;motherboard.vice.com&amp;#x2F;de&amp;#x2F;article&amp;#x2F;784z74&amp;#x2F;33c3--hacker-zeigen-ihre-gadgets&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;motherboard.vice.com&amp;#x2F;de&amp;#x2F;article&amp;#x2F;784z74&amp;#x2F;33c3--hacker-...&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;niklasfauth&amp;#x2F;parametricspeaker&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;niklasfauth&amp;#x2F;parametricspeaker&lt;/a&gt;</text></item></parent_chain></comment><story><title>&quot;Sonic attack&quot; may have been two ultrasonic signals accidentally interfering</title><url>https://spectrum.ieee.org/semiconductors/devices/finally-a-likely-explanation-for-the-sonic-weapon-used-at-the-us-embassy-in-cuba</url></story>