Pitch perception for sequences of pulses alternating different resonance scales.
Minoru Tsuzaki, Toshie Matui, Chihiro Takeshima, Toshio Irino · The Journal of the Acoustical Society of America · 2011
Vowels are produced as a sequence of vocal tract impulse responses which are periodically excited by glottal pulses. Each impulse response reflects the shape and the size of the vocal tract. The size, i.e., the resonance scale, is kept almost constant in the normal speech sounds. It has been found that we can sensitively “hear” such size variations in speech and that the size can be a cue to identify the sound source, i.e., the talker. What do we perceive if impulse responses with two different resonance scales are alternatively repeated. Do we perceive an intermediate sized talker speaking the same pitch as the original? Do we perceive two speech streams of the different sized talkers with the half pitch? By answering these questions, we could clarify the auditory mechanisms for detecting size, periodicity, and resonance. The test stimuli were synthesized whose consecutive glottal pulses were alternated between two resonance scales with several degrees. Pitch matching experiments were performed where the listeners could adjust the fundamental frequency of the comparison stimuli whose each pulse had an identical scale factor. To a certain degree of the resonance scale deviation, the subjective pitch appeared to match the original pitch. If the scale deviation exceeded that limit, the pitch went down by an octave.