mistuned harmonics and duplex perception (at)

Subject: mistuned harmonics and duplex perception
Date:    Thu, 17 Dec 1992 21:26:00 -0500

A recent note from Valter Ciocca says: "In support of Al's point that pitch can be affected by grouping, Chris Darwin and I found that the pitch of a complex could be changed by mistuning one of its low-numbered components only when the mistuned component was grouped with the remaining components of the complex." This is a very nice result. Unfortunately, some other studies do not agree with the conclusion. In 1984 I did mistuned harmonic experiments with brief tones, using a 200 Hz complex tone with 7 harmonics, except that the fourth harmonic was mistuned. Experiment 1 found the amount of mistuning required to hear out the mistuned harmonic as a separate entity. For a tone duration of 40 ms this threshold mistuning was 22 Hz (2.75 % of the correct harmonic frequency of 800 Hz). For mistuning less than 22 Hz the complex was a single entity and the mistuned harmonic did not pop out. Experiment 2 measured the shift in the virtual pitch caused by mistuning of the fourth harmonic. (The virtual pitch is in the vicinity of 200 Hz.) Data, Experiment 2: frequency shift shift of the s.d. of the virtual of mistuned 4th virtual pitch pitch match (Hz) (cents) (cents) 0 3 8 2 4 9 6 9 7 10 11 6 20 8 7 30 18 8 40 17 7 Comparison of the two experiments shows that mistuning the fourth harmonic by 30 or 40 Hz led to virtual pitch shifts larger than the s.d. and also caused the mistuned fourth harmonic to pop out as a separate entity. This mistuned harmonic is perceived in a way that is reminiscent of duplex perception in speech, whereby a single acoustical element is perceived in two different ways. A similar conclusion was reached by Moore, Glasberg and Peters [JASA vol 77, 1853 (1985)] who found that with still larger amounts of mistuning the mistuned harmonic made decreasing contributions to the virtual pitch shift but not abruptly so. >From the point of view of auditory organization one has to say that although pitch may be the great organizer, not every experiment will show that unequivocally. Maybe though, Ciocca and Darwin have done a better experiment than we have. Need more information. Bill Hartmann

This message came from the mail archive
maintained by:
DAn Ellis <dpwe@ee.columbia.edu>
Electrical Engineering Dept., Columbia University