3.7 : 感知响度

Place theory and frequency theory are two primary theories that explain how the brain receives pitch information.

Place theory suggests that the brain identifies a sound's pitch by detecting the specific location on the cochlea's basilar membrane, where sound waves activate distinct areas and produce neural signals.

High frequencies cause strong vibrations at the beginning of the cochlea's membrane, while low frequencies produce wider, less localized vibrations.

This theory explains the perception of high-pitched sounds from  5,000 to 20,000 Hz.

According to frequency theory, the entire basilar membrane vibrates at the same frequency as the sound wave. These vibrations generate neural impulses at corresponding rates, allowing the brain to interpret the pitch.

Frequency theory is effective up to 100 Hz, as many neurons have maximal firing rates near this limit.

Volley theory, a variation of frequency theory, applies to tones between 100 and 5,000 Hz. According to this theory, instead of a single neuron, a group of neurons fire at their highest rate, out of sync, to collectively achieve frequencies up to 5,000 Hz.