If the sound spectra of timpani contains only a handful of partials which are near-harmonic at best, how does the human auditory system interpret this information so that we perceive it as a single, coherent pitch, especially when the fundamental frequency itself is absent from the spectrum? This perceptual phenomenon, called the “missing fundamental,” remains one of the central puzzles in auditory neuroscience. 25 26 4
Human pitch perception is a complicated sensory phenomenon involving numerous sciences such as physics, psychology, psycho-physics, physiology, and neurological science. Beginning with the spirited debate between physicists August Seebeck (1805-1849) and Georg Ohm (1789-1854) in the middle of the 19th century, the scientific community has been somewhat divided in their views regarding how humans (mammals in general) perceive pitch. The disagreement between Seebeck and Ohm established two competing frameworks that persist today: temporal periodicity coding and spectral place theory, each of which explains some but not all pitch phenomena. 1 2 5 3
Attempts have been made to create a unified theory of how we perceive pitch by searching for that single parameter of sound and the mechanism that can account for both the pitch of single sine tones and that of complex waveforms. To this day, that search has yielded volumes of information and numerous theories, but modern neuroscience increasingly supports simultaneous parallel processing of multiple pitch cues rather than a single unified mechanism. 4 5
Over the years, pairs of competing theories (and variations thereof) have prevailed in attempting to explain what human pitch is, what processes the human ear uses in coding the information it collects and what part(s) of the auditory cortex the brain uses for processing the information. Current evidence suggests that at least two distinct neural mechanisms, place coding and temporal coding, operate in parallel to extract pitch information. 5
Key open questions remain: How is spectral information converted to neural firing patterns in the cochlea? How do temporal and place cues integrate in the auditory cortex? What role does prior experience and expectation play in pitch perception?
The historical debate over pitch perception has always turned on a basic question: what information does the ear actually deliver to the brain when a sound is heard? Before we can follow Seebeck, Ohm, and Helmholtz into their disagreements, we need a simple map of the auditory pathway itself, how sound is transduced into neural signals, and what kinds of “codes” (place and timing) are available at the earliest stages. The next page provides a condensed overview of auditory transduction and introduces the two complementary coding mechanisms that underpin nearly every later theory of pitch.