Normally, if you hear a sound, you have some idea of where the sound came from. But when a scuba diver hears a sound underwater, it is virtually impossible to tell where it came from.

1. Why?

2. Can you suggest some form of underwater hearing aid type device that would allow more accurate underwater sound localization?

Answering Sam and Jonathan; The amplitude of a sound wave is inversly proportional to the square of the distance it has traveled.

It doesn't matter how slow or fast a wave moves. Even the light (the fastest possible wave) follows this law.

To see why, think of the energy the wave is carrying. As the wave expands spherically it's fixed energy is spread out over a larger surface. The surface goes like 4*pi*r^2, and so the energy per unit area (what we actually hear)  decreases with the square of the distance.

I'm also confused about the time difference. How could you know where a constant humming noise is comming from?. As I see it, the time difference can only be used when you FIRST hear a sound, or when you STOP hearing it. How could you know where a constant sound is?. Also, even for an air wave moving a 300 m/s, we would only have about 5 microseconds to register a sound difference. The eyes (which are much better than our ears) can only percive 20 microsecond time lapses (this from knowing that after 50 frames per second the percived quality of a movie is constant).

Edit; The units I used for my times are wrong. I meant to say that the difference of sound in air is 0.5 miliseconds  and the time lapses the eye can percive are have lower limit of about 20 miliseconds.

Edited on April 14, 2005, 1:51 pm

Posted by ajosin on 2005-04-14 13:42:15