What is the sound of two hands clapping?

Ever notice how men clap differently from women? If you have, you've probably imagined it. Bruno Repp, who has spent years studying the brief, percussive consonants p, t, and k in human speech, took time out to investigate the percussive sound of clapping. He found that sex and the size of one's hands have very little to do with the timbre of one's applause.

Repp, a psychologist and speech scientist at Haskins Laboratories in New Haven, Conn., asked a group of twenty people who knew one another to identify their acquaintances by the sound of their applause. All performed abysmally. On average, they could correctly identify only eleven per cent of the claps they heard. In fact, they couldn't even guess the sex of the clapper.

That doesn't mean, though, that applauders don't have a signature clap. Repp had the clappers give ten samples each of their applause for a computer program to sort according to amplitude and frequency. Unlike the human listeners, the computer correctly identified clappers ninety per cent of the time. Repp says this indicates that there are things people don't pay attention to that make each person's applause distinctive. Perhaps because people don't often listen to each other clapping, says Repp, they're ignorant of these factors.

Humans are alert, however, to the position of the hands that make the sound. Bright timbres are made by hitting the fingers of one hand against the palm of the other, whereas dark timbres are made by slapping the two palms together, and everyone realizes this. When Repp asked his listeners to guess how various applauders held their hands, they rarely mistook a finger clap for a palm clap.

This didn't surprise Repp. ''The very brief consonant sounds you make when you open your lips and put your tongue to the roof of your mouth give information about the shape of your vocal tract and the position of the jaw and tongue,'' he says. ''And the same logic applies to non-speech sounds. Sounds reflect the configuration of parts of the instrument.''

Speech and clapping have something else in common. The average duration of a syllable in normal speech is just about the same as the average rate of claps -- four per second. ''Maybe it's a general function of what's comfortable,'' says Repp, ''but I prefer to think it's just a coincidence.''

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