Academic journal article Attention, Perception and Psychophysics

Pitch Perception

Academic journal article Attention, Perception and Psychophysics

Pitch Perception

Article excerpt

This article is a review of the psychophysical study of pitch perception. The history of the study of pitch has seen a continual competition between spectral and temporal theories of pitch perception. The pitch of complex stimuli is likely based on the temporal regularities in a sound's waveform, with the strongest pitches occurring for stimuli with low-frequency components. Thus, temporal models, especially those based on autocorrelation-like processes, appear to account for the majority of the data.

Pitch may be the most important perceptual feature of sound. Music without pitch would be drumbeats, speech without pitch processing would be whispers, and identifying sound sources without using pitch would be severely limited. The study of the perceptual attributes of pitch permeates the history of the study of sound, dating back almost to the beginnings of recorded time. For instance, Pythagoras established the existence of relationships between the length of plucked strings and the octave. The study of pitch perception is the study of the relationships among the physical properties of sound, its neural transforms, and the perception of pitch. The quest for a theory that establishes such a physical-perceptual (psychophysical) relationship is hundreds of years old, and there is still debate concerning what aspects of sound lead to the perception of pitch in the wide variety of contexts in which pitch is a major perceptual attribute of sound.

Sound, Auditory Periphery, and Pitch

Sound can be described in several ways; it is usually defined as comprising three physical properties: frequency, magnitude, and time/phase. The auditory periphery provides neural codes for each of these dimensions, so it would not seem to be very difficult to find a way to relate one or more of these properties to the perception of pitch. But it has been essentially impossible to do so in such a way as to establish a unified account of pitch perception for the wide variety of conditions leading to the perception of pitch. In the elemental case of a simple sound with a single frequency (i.e., a sinusoidal tonal sound), the frequency is its pitch. Even this simple sound has two representations: spectral and temporal. In the spectral domain, the sound is characterized as being a simple spectrum with a single spectral component at a given frequency and with a given magnitude and starting phase. The frequency of the spectral component is the sound's perceived pitch. The sound can also be equivalently represented by a sinusoidal time-pressure waveform. The reciprocal of the period of the waveform is also the pitch of such a simple sound. The time-pressure waveform and the spectrum are inverse functions of each other, in that the spectrum is the Fourier transform of the time-pressure waveform. Thus, one representation (e.g., the time-pressure waveform) can be transformed (via the Fourier transform) into the other representation (e.g., the spectral representation). So, it would appear that it would be difficult to decide between a spectral and a temporal explanation of pitch, in that one explanation is a simple transform of the other. Such a physical reality has complicated the ability to develop theories of pitch perception.

The description of the physical aspects of sounds is not the only basis for considering pitch processing. Sound must pass through the auditory system and, in so doing, is transformed significantly. The processing of sound by auditory mechanisms, especially peripheral structures, alters the representation of sound, and, as a consequence, these alterations affect the ways in which spectra and time-pressure waveforms contribute to pitch perception. At present, theories of pitch processing are based more on the possible neural representation of sound at the output of the auditory periphery than on the purely physical properties of sound. Even so, there remain two classes of theories: spectral and temporal. Testing one type of theory against the other is always complicated by the equivalence of the two views of sound. …

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