Helping the Deaf Hear Music

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CAMP sidesteps differences in taste by stripping down music to three basic components--pitch, timbre, and melody--and systematically assessing how well users perceive each.

Pitchperception is measured when the program plays two tones a short interval apart and asks the user to decide which is higher pitched. When the user is correct, the program gives her tones that are closer together. When she isn't correct, it gives her tones that are farther apart. Over a number of trials, the program works out the closest interval that she can reliably differentiate. It's a relatively easy test because all the listener has to do is determine which of two tones is the higher one.

Timbre perception is measured by playing the same note on eight different instruments. The user is asked to identify which instrument she hears. For example, the subject might be asked whether a particular note was played on a piano, a flute, or a saxophone. Timbre is perhaps the hardest aspect of music to define, but it provides a sensitive measure of a user's ability to hear distinct but subtle differences.

Melody perception is measured in a highly unusual way. The test uses familiar tunes such as "Frère Jacques" and "Three Blind Mice." But anyone would recognize "Frère Jacques" from the lyrics, so the lyrics are taken out. So is the rhythm--that is, the timing and duration of the notes. What is left is a string of equally spaced notes of equal duration: the melody and nothing but the melody.

I was one of the test subjects in early trials of CAMP. The first time I took the test I used my old software, Hi-Res. The pitch testing was fairly easy: I identified most of the frequencies correctly 75 percent of the time. I didn't do as well on the timbre test, getting about 40 percent right.

But the melody test bewildered me. The very first tune sounded like beep boop beep beep boop beep bip beep boop. I stared at the computer. What the hell was that?

I "identified" it by choosing a song title at random, since I had no clue what it was, and waited for the next tune. Beep boop beep beep boop beep bip beep boop.

And the next. Beep boop beep beep boop beep bip beep boop.

Were they even different?

My score was less than 10 percent. I talked to Chad Ruffin, one of the designers of the test, who had a cochlear implant himself. How well, I wanted to know, would a person who hears normally do on the melody test? About 100 percent, he told me.