Frequency theory proposes that the pitch of a sound is coded by the rate of nerve impulses traveling up the auditory nerve. A 200 Hz tone produces 200 impulses per second; a higher tone produces a faster rate.

The theory works well for low frequencies. Individual neurons can fire in synchrony with the sound wave up to a few hundred hertz. For higher frequencies, no single neuron can keep pace. The volley principle extends the theory by proposing that groups of neurons share the load, firing in staggered groups whose combined rate matches the frequency of the sound.

Frequency theory is usually paired with place theory, which holds that different frequencies excite different places along the basilar membrane. Modern accounts treat the two as complementary: place coding dominates at high frequencies, frequency (or temporal) coding at low frequencies, and both operate in the middle range.

When the auditory system tracks the tempo of a sound wave, frequency theory describes the mechanism.