ASA 21 - Shift Of Virtual Pitch

Description

A tone having strong partials with frequencies of 800, 1000, and 1200 Hz will have a virtual pitch corresponding to the 200 Hz missing fundamental, as in Demonstration 20. If each of these partials is shifted upward by 20 Hz, however, they are no longer exact harmonics of any fundamental frequency around 200 Hz. The auditory system will accept them as being "nearly harmonic" and identify a virtual pitch slightly above 200 Hz (approximately 1/3(820/4 + 1020/5 + 1220/6) = 204 Hz in this case). The auditory system appears to search for a "nearly common factor" in the frequencies of the partials.

Note that if the virtual pitch were created by some kind of distortion, the resulting difference tone would remain at 200 Hz when the partials were shifted upward by the same amount.

In this demonstration, the three partials in a complex tone, 0.5 s in duration, are shifted upward in ten 20-Hz steps while maintaining a 200-Hz spacing between partials. You will almost certainly hear a virtual pitch that rises from 200 to about 1/3( 1000/4 + 1200/5 + 1400/6) = 241 Hz. At the same time, you may have noticed a second rising virtual pitch that ends up at 1/3(1000/5 + 1200/6 + 1400/7) = 200 Hz and possibly even a third one, as shown in Fig. 2 in Schouten et al. (1962)

In the second part of the demonstration it is shown that virtual pitches of a complex tone having partials of 800, 1000, and 1200 Hz and one having partials of 850, 1050, and 1250 Hz can be matched to harmonic complex tones with fundamentals of 200 and 210 Hz respectively.

References

J.F.Schouten, R.L.Ritz and B.L.Cardozo (1962), "Pitch of the residue," J. Acoust. Soc. Am. 34, 1418-1424.

G.F.Smoorenburg (1970), "Pitch perception of two-frequency stimuli," J. Acoust. Soc. Am. 48, 926-942.

Frequency

		Time Delay

Transcript

You will hear a three-tone harmonic complex with its partials shifted upward in equal steps until the complex is harmonic again. The sequence is repeated once.

Frequency

		Time Delay

Transcript

Now you hear a three-tone complex of 800, 1000 and 1200 Hz, followed by a complex of 850, 1050 and 1250 Hz. As you can hear, their virtual pitches are well matched by the regular harmonic tones with fundamentals of 200 and 210 Hz. The sequence is repeated once.