<story><title>The human ear detects half a millisecond delay in sound</title><url>https://www.aalto.fi/en/news/the-human-ear-detects-half-a-millisecond-delay-in-sound</url></story><parent_chain><item><author>function_seven</author><text>My dad bought an Isuzu Impulse in 1985. It had a fancy OEM stereo system with Technics branding, and a button for the driver to toggle the imaging. The button was on the 7-band graphic EQ that game with the car. (I don&amp;#x27;t think I&amp;#x27;ve ever seen another factory stereo with physical EQ sliders like that.)&lt;p&gt;It was magic, if you were sitting in the driver&amp;#x27;s seat. Toggling that button made the sound switch from &amp;quot;okay&amp;quot; to &amp;quot;magically spatial.&amp;quot;&lt;p&gt;I&amp;#x27;m pretty sure that lead to a conversation about how we locate sounds. Also wonder how it was implemented in 1985. I doubt there were DSP chips in there. What&amp;#x27;s the &amp;quot;simple&amp;quot; way of adding delay to some speakers?</text></item><item><author>bob1029</author><text>Its amazing how much difference .5ms can make in stereo imaging. Any decent home audio receiver has the ability to set the distance of each speaker individually so that you can compensate for physical placement constraints.&lt;p&gt;If you get a stereo pair perfectly locked in on delay to eardrums, you can produce an extremely compelling listening experience for those in a very specific region of the room.&lt;p&gt;Finding out about all this can be revolutionary for some music enthusiasts. Once you get a good listening setup (or headphones), you start going through old things to see how the &amp;quot;stage presence&amp;quot; sounds, or if you are now able to physically place each instrument in the virtual space.</text></item></parent_chain><comment><author>jasonwatkinspdx</author><text>&amp;gt; I&amp;#x27;m pretty sure that lead to a conversation about how we locate sounds.&lt;p&gt;So, psychoacoustics is incredibly complicated. There&amp;#x27;s something like 13 different mechanisms that co-operate in sound localization.&lt;p&gt;However, the bulk of it was known quite a bit before 1985, and had nothing to do with the &amp;quot;spatialize me&amp;quot; button on a specific car stereo.&lt;p&gt;There&amp;#x27;s no simple way to add a delay to some speakers unless you&amp;#x27;re working in the digital domain. In analog you have two basic choices. With passive components, you build a ladder filter, which is as the name suggests, just a long chain of low pass or all pass filters. Each &amp;quot;rung&amp;quot; only adds group delay on the scale of a couple usec, so these get very big and expensive fast. They also suffer from accumulated imprecision issues. With active components you can create a feedback loop through an op amp. This is how guitar delay pedals work, but the more delay you have the more distortion you introduce.&lt;p&gt;Technically there&amp;#x27;s a 3rd way: extremely long wires, but that&amp;#x27;s basically never practical.&lt;p&gt;Thankfully these days everything starts out in the digital domain, so you just need a controllable fifo before the DAC. Entry level home theater receivers have had this since circa 2000.</text></comment>
<story><title>The human ear detects half a millisecond delay in sound</title><url>https://www.aalto.fi/en/news/the-human-ear-detects-half-a-millisecond-delay-in-sound</url></story><parent_chain><item><author>function_seven</author><text>My dad bought an Isuzu Impulse in 1985. It had a fancy OEM stereo system with Technics branding, and a button for the driver to toggle the imaging. The button was on the 7-band graphic EQ that game with the car. (I don&amp;#x27;t think I&amp;#x27;ve ever seen another factory stereo with physical EQ sliders like that.)&lt;p&gt;It was magic, if you were sitting in the driver&amp;#x27;s seat. Toggling that button made the sound switch from &amp;quot;okay&amp;quot; to &amp;quot;magically spatial.&amp;quot;&lt;p&gt;I&amp;#x27;m pretty sure that lead to a conversation about how we locate sounds. Also wonder how it was implemented in 1985. I doubt there were DSP chips in there. What&amp;#x27;s the &amp;quot;simple&amp;quot; way of adding delay to some speakers?</text></item><item><author>bob1029</author><text>Its amazing how much difference .5ms can make in stereo imaging. Any decent home audio receiver has the ability to set the distance of each speaker individually so that you can compensate for physical placement constraints.&lt;p&gt;If you get a stereo pair perfectly locked in on delay to eardrums, you can produce an extremely compelling listening experience for those in a very specific region of the room.&lt;p&gt;Finding out about all this can be revolutionary for some music enthusiasts. Once you get a good listening setup (or headphones), you start going through old things to see how the &amp;quot;stage presence&amp;quot; sounds, or if you are now able to physically place each instrument in the virtual space.</text></item></parent_chain><comment><author>wgj</author><text>At that time, the most common way to do stereo enhancement was to decrease the L + R component of the stereo signal. [0] L+R&amp;#x2F;L-R was (and still is) a common way to encode stereo signals, including for FM radio. [1]&lt;p&gt;The impact on the stereo field by just changing the mix of these two components is profound. No signal delay needed.&lt;p&gt;For signals that are simple L and R, sum them to get L+R and difference to get L-R. So you can use this technique on any stereo source.&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.sweetwater.com&amp;#x2F;insync&amp;#x2F;stereo-enhancement-work-more-better&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.sweetwater.com&amp;#x2F;insync&amp;#x2F;stereo-enhancement-work-mo...&lt;/a&gt;
[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;FM_broadcasting#Stereo_FM&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;FM_broadcasting#Stereo_FM&lt;/a&gt;</text></comment>