20070709 - 3D Audio and KEMAR Data
++ + + +3D audio is a weird science. +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. +This is how we can tell what direction a sound is coming from. +And of course, all of our bodies are different, so we each hear differently, and thus there is no perfect solution to 3D audio. +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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+Ultimately writing a system for 3D Audio requires data of exactly how the left and right ears filter sound based on direction.
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+Luckily Bill Gardner and Keith Martin from MIT have publicly provided such data using a KEMAR dummy head. +
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+ +Interpreting the KEMAR Data +
+Their Compact HRTF measurements tarball provides the data in a ready to use format, +368 directional stereo recordings (each 128 samples in length) of the corrected impulse response captured from mics in the KEMAR ears. +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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+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, +and then filters input from the audio in jack and plays out the directional audio. +The impulse sample (time domain) for the left and right ears (green and blue) is shown on the lower left. +While the FFT results (frequency domain) is shown on the right. + + + + +