Why is it so hard to pinpoint exactly where some electronic beeping sounds are coming from?


Why is it so hard to pinpoint exactly where some electronic beeping sounds are coming from?

In: Physics

There is two reasons. Firstly we are unable to determine the exact direction of a sound from our two ears. This is why you move your head around to try to determine where a sound comes from. But with a short beep you do not have enough time to move your head to get the source of the sound. And secondly a single frequency will very easily create interferance patterns as there are multiple paths from the source to your ears with different lengths. So the sound becomes stronger and weaker depending on where in the room you are without it having anything to do with where the sound comes from. A high pitch beeping is one of the worst sounds to locate for this exact reason.

When something makes a noise it projects loose sound waves all around it. Sound waves is essentially the physical particles in the air vibrating which gradually get wider and wider, making it difficult to pinpoint the location. The closer you get the sharper the noise. The vibrations can break up a lot when they hit physical barriers like a wall or even clothing.

You have two ears, because your ears are in different places and sound isn’t instant there will be a slight delay between what you hear in either ear. If the sound is coming from the left your left ear will hear it slightly before your right ear.

This is what your brain uses to figure out where a sound is coming from. Electronic beeping usually have a lot of patterns to the soundwaves and you brain is unable to tell if the left ear is ahead or behind of the right ear since everything repeats so often.

Ya. Too bad. I have a battery powered smoke detector enclosed in my drywalled ceiling. Thx contractor. Thx Duracell. Fukien thing has been chirping for about 4 months.

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)