Where’s That Sound Coming From?

Long ago, researchers concluded that a diver could pinpoint the source of a sound underwater within 10 degrees, which should make locating the sound source easy. However, any diver who has had to locate a sound source knows it's tough.

If your buddy hits his knife against his tank when you're on the surface, you can turn to him because you can sense exactly where the sound comes from. Not so underwater, where you might sense that it's coming from behind you, but you have to look around for a visual clue to locate it. Indeed, sound localization underwater is difficult, and 10 degrees seems far too narrow.

So researchers at the Naval Submarine Medical Research Lab in Groton, CT, set out to see just how accurate 10 degrees was. They arranged sound projectors on a steel circle three meters in radius, with subjects sitting in the center, and found that at best, divers were able to pinpoint sounds at approximately 20 to 30 degrees, between 500 and 4000 hertz, significantly poorer than previous findings. (The human hearing range is between 12 and 20,000 Hz.)

How can you use that research? Well, for example, if you hear a boat engine but can't see the boat, face toward where you think the sound emanates, and the boat should be somewhere within a 30-degree arc ahead of you. Keep in mind, if you swim to where you think the sound comes from, you can still miss the boat.

- - Ben Davison