Dear Xueliang Zhang,
I was intrigued by the interchange between you, Yoshitaka Nakajima, and Al Bregman, and did some listening, diotically through headphones, to stimuli consisting of the first 10 harmonics of 100 Hz alternating with the 5 even harmonics of that stimulus (all harmonics were presented at the same level). With on/off times for each complex matched at either 0.5 sec or 1.0 sec (10 ms rise/fall), I hear a fully continous 200-Hz tone that matches the intensity and timbre of the isolated even-harmonic complex. More interesting, however, is that the 10-component “all-harmonic” stimulus, which is heard intermittently, has not only the 100-Hz pitch of that complex but also retains the loudness and timbre of the all-harmonic stimulus as heard when it is presented in isolation. Were the even harmonics of the all-harmonic complex exclusively allocated to support perception of the continuous 200-Hz complex tone -- leaving only the odd-harmonics to support perception of the 100 Hz tone -- we would expect both a reduction in loudness and a clear shift in timbre to the “hollow” quality characteristic of odd-harmonic signals. This suggests that the “priming” or “capture” effect observed with complex tones provides an example of duplex perception that requires neither a verbal stimulus nor dichotic presentation. As I recall, Al Bregman has previously suggested that such an effect might occur when nonverbal stimulus input is strongly ambiguous.
This use of the even-harmonic components to support two simultaneous percepts (that of both the intermittent “all-harmonic” tone and the continuous even-harmonic tone) contrasts sharply with the processing underlying the general phenomenon of illusory continuity that is observed when one sound alternates with a higher-intensity, potential masking sound. The latter effect, which has been called auditory induction (Warren, 1972), occurs with a wide variety of signals, such as tones alternating with other tones, noise alternating with higher intensity noise, or speech interrupted by noise (phonemic restoration). This type of continuity, in which there are no exactly matching components to be found between the alternating signals, does appear to involve subtractive or exclusive allocation. For interrupted tones, noise, or speech, continuity is obtained at the expense of the interrupting signal, which is reduced in loudness by an amount proportional to the extent the illusion (Warren et al., 1994).
Warren, R. M., Obusek, C. and Ackroff, J. M. (1972). Auditory induction: Perceptual synthesis of absent sounds. Science, 176, 1149-1151.
Warren, R. M., Bashford, J. A., Jr., Healy, E. W., and Brubaker, B. S. (1994). Auditory induction: Reciprocal changes in alternating sounds. Perception & Psychophysics, 55, 313-322.
On Mar 19, 2009, at 5:24 AM, xlzhang wrote: