p a p e r s
p r e s e n t a t i o n s
Vassilakis, P.N. (1998). The
first pitch-shift effect as a Doppler effect: a simple physical
explanation to a complex perceptual phenomenon. J. Acoust. Soc. Am.,
104(3/2): 1799 (presented at the 136th meeting of the Acoustical Society of America, Norfolk, VA).
The first pitch-shift effect describes the relationship
between pitch and center frequency of complex stimuli with equally spaced
components and fixed frequency spacing (: f0). It
mathematically by a saw-tooth function in a model introduced by de Boer
[Doctoral dissertation, University of Amsterdam, (1956)]. Researchers
usually favor a more ambiguous frequency-shift/pitch-shift relationship that
better justifies the generally accepted explanation (: perceptual detection of
a wave signal’s time-fine-structure). Pilot experiments, however, indicate
a) The patterned pitch ambiguities reported by previous studies may be artifacts of experimental
design, not a challenge to de Boer’s model.
b) No model accounts for
the present study’s reported pitch for frequency shifts: f0/2.
The explanation introduced presently argues that:
a) Modulations resulting from wave superposition are waves themselves, with velocity (VGroup) that
is independent from the velocity of their constituent components (VPhase).
b) Uniform frequency shifts of a complex wave’s
components change the relationship
between VGroup and VPhase,
changing the effective frequency of the emerging modulations relative to a
fixed point in the medium of propagation.
These relative speed/frequency changes predict pitch shifts
that agree with observation, (including frequency-shifts: f0/2), making
the first pitch-shift effect a version of the Doppler effect.