Why is it so hard to pinpoint exactly where some electronic beeping sounds are coming from?
In: Physics
Hearing scientist here, with a PhD in sound localisation.
Electronic beeps are usually very clean sine waves, like the stereotypical wave. They are often high pitched.
One of the ways we would out where a round comes from is by the difference in arrival time between the two ears. The sound arrives sooner at the nearer ear. But this only really works for complicated sounds with lots of different frequencies (pitches) or lower sounds. Why? Well for higher sounds, the wavelength is close to the size of the head. If you miss the start of the sound, it’s impossible to tell which ear is ahead and which is behind because each copy of the wave looks the same. With lower sounds, it’s easier because the size of the head sets a limit on how ahead or behind a wave could be. With more complicated sounds, you can compare the whole complicated signal to work out which ear got the earlier ‘copy’.
The other main way we work out locations is using the level difference between the two ears. This works best for higher sounds because lower sounds can bend around the head better and so the levels are more similar.
If the sound happens to be in the middle of these two ranges, you can’t really use either method to work out where it is. Even if you *can* use level differences, the head is pretty symmetric. We can tell left from right, but it’s hard to work out front from back or top from bottom. The way round this is by moving your head. But if the sounds are short beeps, you’ve barely got any chance to figure it out before the beep ends. It makes it tricky for your brain to combine the info from successive beeps.
This is the reason that Tesco vans in the UK now use a burst of noise (like static on a radio) instead of a beep when they reverse.
Edit: thanks, kind strangers 🙂 happy to be of help. I guess I’ll take this opportunity to tell you to not use cotton buds (Q-tips) unless you want a perforated eardrum, and remember to wear protection. Ear protection, that is. Gigs are loud! Get some decent earplugs. Noise-induced hearing loss isn’t fun, and there’s nothing we can do to cure it (…yet)
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