B. Determination of Pitch and Loudness

1. Pitch sensation is mediated by two mechanisms

a. place mechanism: which region of the basilar membrane is maximally excited; e.g. high frequencies near base, lower frequencies toward apex (main mechanism, particularly for higher frequencies)

b. volley mechanism: at lower frequencies, a volley of APs is generated at the same frequency as the sound wave

2. Loudness depends on

a. how strongly individual hair cells are stimulated

b. how many hair cell axons are recruited

Note application to cochlear implant (==>)