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db48x • today at 7:37 AM • 3 replies • view on HN

It’s because it doesn’t have enough overtones, or a notable attack. You might have noticed that some trucks these days make a weird noise when they back up instead of a beep. They’re using white noise because it’s easier to locate; it has many overtones that allow your brain to pick the sound out of the background more easily, and thus more easily correlate the signals from both ears. You get a much more accurate location just from hearing that sound than you ever could with a pure tone.


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HPsquared • today at 9:30 AM

Consider a pure sine wave, it's harder (in theory anyway) to match the signals from the left and right ears, and identify the time delay between the two signals: each cycle of the wave is just like the others, so there's no distinct signature to match and say "the sound reached the left ear 0.5 ms before it reached the right ear". This is especially the case for higher frequencies where there can be something like aliasing.

Animal species sometimes use this in different sounds they make. An alarm call has that kind of "smooth tone" characteristic, so a predator can't locate the source of the sound but it still works to raise the alarm. Meanwhile more social sounds are more "chirpy" and sharp, so they can locate each other.

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thenthenthen • today at 7:56 AM

Interesting! I also feel the pulse is just to short… starting to question yourself if you actually heard something or that you are imagining it. Here the cars and trucks play musicals tunes or a crappy voice recording hahah

tourmalinetaco • today at 8:22 AM

That makes sense; we were searching for a family member’s blood sugar monitor just today and it barely seemed to come from any single direction. Ultimately it wasn’t the sound itself but the loudness of it that let us find it, because a blanket got shoved over it mid-search that we could deduce from there.