Time intensity trading

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Move the mouse cursor over the grid below to hear a harmonics complex tone with ILDs and ITDs as indicated.

You should listen to these sounds over headphones, and this demo may not work for you if you have a significant hearing loss in one ear, or if the sound card on your computer is of poor quality and does not separate the two stereo channels well.

Positive ILDs and ITDs should make the sound appear to come from the right. Hence, the sounds toward the top right should sound the furthest right, the ones in the bottom left the furthest left. (Make sure you have your headphones on the right way around.)

The curious thing to observe here is that, if you start from the middle, you can move the sound right either by moving the mouse cursor up, or by moving it right. You change the sounds in two very different ways (in one case you change the timing between the ears, in the other you change the relative sound intensity) but although the manipulations are very different in nature, they produce the same effect: the sound appears to come from the right. Can you tell by listening carefully whether the sound percept moves because of timing or intensity cues?

Another thing to try is this: start from the middle, move the sound right by moving the cursor right, then move the cursor down. As you move the cursor down the sound should appear to move back toward the middle, because the timing and intensity cues now point in opposite directions, and your brain perceives the sound at a compromise position somewhere in between.

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