A spectral contrast illusion
Diana Deutsch, F. Richard Moore · The Journal of the Acoustical Society of America · 1984
A new illusion is described, produced by presenting two repeating sequences of Shepard tones, one to each ear. Each tone consisted of several sinusoidal components separated by octaves, and the tones were generated under various fixed spectral amplitude envelopes. The pitches were as in the scale illusion [D. Deutsch, J. Acoust. Soc. Am. 57, 1156–1160 (1975)], omitting those standing in octave relation. Thus B-E-G-G-E-B was presented to one ear, while D-A-F-F-A-D was presented to the other ear. Musically trained subjects notated separately the sequences that they heard in each ear. Most subjects reorganized the tones in accordance with pitch proximity, so that they obtained the illusion of B-A-G-G-A-B in one ear, together with D-E-F-F-E-D in the other ear. The apparent locations of the two sequences were often independent of the positioning of the earphones. Further, the subjects generally reported the two sequences as in different octaves. Analogous effects were obtained with binaural presentation of simultaneously ascending and descending Risset glides. [Work supported by NIMH.]