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41 lines
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HTML
41 lines
1.8 KiB
HTML
<html><head><link rel="stylesheet" href="style.css"></head><body><div class="page">
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<h1>20070709 - 3D Audio and KEMAR Data</h1>
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<br>
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3D audio is a weird science.
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Basically the body (and shape of the ear) itself filters the sound which reaches each ear differently based on the direction of the incoming sound.
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This is how we can tell what direction a sound is coming from.
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And of course, all of our bodies are different, so we each hear differently, and thus there is no perfect solution to 3D audio.
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While elevation cues are greatly effected by ear shape, azimuth (left to right) and distance cues are similar between most people.
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<br>
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<br>
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Ultimately writing a system for 3D Audio requires data of exactly how the left and right ears filter sound based on direction.<br>
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<br>
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<a href="http://sound.media.mit.edu/KEMAR.html">Luckily Bill Gardner and Keith Martin from MIT have publicly provided such data using a KEMAR dummy head</a>.
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<br>
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<br>
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<b>Interpreting the KEMAR Data</b>
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<br>
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Their Compact HRTF measurements tarball provides the data in a ready to use format,
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368 directional stereo recordings (each 128 samples in length) of the corrected impulse response captured from mics in the KEMAR ears.
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Simply run your FFT on the impulse samples and you have the frequency response (or filtering each ear does) based on the 368 directions sampled in the data.
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<br>
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<br>
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<center><img src="20070709.jpg"></center>
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<br>
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This is a screen shot of a simple program I wrote to checkout the data, which enables the user to select a azimuth and elevation,
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and then filters input from the audio in jack and plays out the directional audio.
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The impulse sample (time domain) for the left and right ears (green and blue) is shown on the lower left.
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While the FFT results (frequency domain) is shown on the right.
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</div></body></html>
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