Further evidence for an autonomous processing of pitch in auditory short-term memory

In four related experiments, subjects had to discriminate between the presence or absence of a frequency difference between two pure tones separated by 4.3 s. The interference effects of other tones (I), inserted during the retention interval, were investigated. A previous study [C. Semal and L. Demany, J. Acoust. Soc. Am. 89, 2404-2410 (1991)] had shown that subjects' performance strongly depended on the pitch relations between the test tones and the I tones, but not on the spectral composition of the I tones. This suggested that the mnemonic system processing pitch is deaf to sharpness of timbre. In the present study, the I tones could differ or not from the test tones in intensity (by +/- 6 or 15 dB) or in amplitude envelope (periodic as well as aperiodic envelopes were used). It was found that such differences had very little effect on performance, suggesting that the mnemonic system processing pitch is deaf to loudness and to dynamic aspects of timbre. However, for I tones with a dense spectrum in the vicinity of the test tones' frequencies, widening the I tones' spectrum improved performance, probably because this spectral widening decreased the salience of the I tones' pitches.