05-Thesoundsofsilence - 6 The Sounds of Silence W h e n I...

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The Sounds of Silence I was a student I worked in a laboratory at McGill University that studied auditory perception. Using a computer, I would synthesize trains of overlapping tones and determine whether they sounded like one rich sound or two pure ones. One Monday morning I had an odd experience: the tones suddenly turned into a chorus of screaming munchkins. Like this: (beep boop-boop) (beep boop-boop) (beep boop-boop) HUMPTY-DUMPTY- HUMPTY-DUMPTY-HUMPTY-DUMPTY (beep boop-boop) (beep boop-boop) HUMPTY-DUMPTY-HUMPTY-DUMPTY-HUMPTY- HUMPTY-DUMPTY-DUMPTY (beep boop-boop) (beep boop- boop) (beep boop-boop) HUMPTY-DUMPTY (beep boop-boop) HUMPTY-HUMPTY-HUMPTY-DUMPTY (beep boop-boop). I checked the oscilloscope: two streams of tones, as programmed. The effect had to be perceptual. With a bit of effort I could go back and forth, hearing the sound as either beeps or munchkins. When a fellow student entered, I recounted my discovery, mentioning that I couldn't wait to tell Professor Bregman, who directed the laboratory. She offered some advice: don't tell anyone, except perhaps Professor Poser (who directed the psychopathology program). Years later I discovered what I had discovered. The psychologists Robert Remez, David Pisoni, and their colleagues, braver men than I am, published an article in Science on "sine-wave speech." They synthesized three simultaneous wavering tones. Physically, the sound was nothing at all like speech, but the tones followed the same con- tours as the bands of energy in the sentence "Where were you a 158 6 When
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The Sounds of Silence 159 year ago?" Volunteers described what they heard as "science fiction sounds" or "computer bleeps." A second group of volunteers was told that the sounds had been generated by a bad speech synthesizer. They were able to make out many of the words, and a quarter of them could write down the sentence perfectly. The brain can hear speech content in sounds that have only the remotest resemblance to speech. Indeed, sine-wave speech is how mynah birds fool us. They have a valve on each bronchial tube and can control them indepen- dently, producing two wavering tones which we hear as speech. Our brains can flip between hearing something as a bleep and hearing it as a word because phonetic perception is like a sixth sense. When we listen to speech the actual sounds go in one ear and out the other; what we perceive is language. Our experience of words and syllables, of the "b"-ness of b and the "ee"-ness of ee, is as separable from our experience of pitch and loudness as lyrics are from a score. Sometimes, as in sine-wave speech, the senses of hearing and phonetics compete over which gets to interpret a sound, and our perception jumps back and forth. Sometimes the two senses simultaneously interpret a single sound. If one takes a tape recording of da, electronically removes the initial chirplike portion that distin- guishes the da from ga and ka, and plays the chirp to one ear and the residue to the other, what people hear is a chirp in one ear and
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This note was uploaded on 03/19/2012 for the course BA 232 taught by Professor Anishkoshy during the Spring '12 term at Faculty of English Commerce Ain Shams University.

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05-Thesoundsofsilence - 6 The Sounds of Silence W h e n I...

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