How does the auditory nerve signal sound frequency below 1 kilohertz?

For sounds with frequencies below 1 kilohertz, the auditory nerve signals frequency through a mechanism known as phase-locking.1

While the cochlea utilizes "place theory"—where different frequencies stimulate specific regions along the basilar membrane—this spatial mapping is supplemented by temporal coding at lower frequencies. In this process, nerve fibres fire at regularly recurring intervals that correspond to a specific phase of the incoming sound wave.21

Essentially, the rate and timing of the impulses generated by the auditory nerve fibres provide the brain with information about the frequency of the sound. This temporal information, combined with the place of maximum vibration on the basilar membrane, allows the auditory system to accurately distinguish pitch for lower-frequency tones.21