Abstract:

Historically, auditory pitch is considered to be principally a function of acoustic frequency with only a small effect due to absolute intensity. Yet, when tones are Doppler shifted, the pitch dramatically rises and falls with dynamic intensity. This study uses a matching procedure to document the magnitude of pitch drop of dynamic Doppler stimuli. Listeners heard Doppler-shifted tones with a mean frequency of either 1046 or 175 Hz, a total fall of 2 semitones, and an intensity change of 58 to 86 dB and back to 58 dB. They compared this drop to a pair of 75-dB, 0.25-s discrete tones that dropped in frequency by intervals ranging from 0 to 24 semitones. The average match between experienced sizes of Doppler and discrete pitch change occurred at a discrete drop of 8 semitones, four times larger than the actual Doppler frequency change. This effect opposes and is an order of magnitude larger than the well known effect due to discrete intensity change. It is proposed that the interaction between dynamic pitch and loudness reflects a natural correlation between changes in frequency and intensity that is neurally encoded to facilitate processing of meaningful acoustic patterns.