What allows the cochlea to distinguish between different frequencies of sound?

The cochlea contains specialized hair cells that are sensitive to different frequencies of sound. These hair cells are situated along the basilar membrane, which has varying stiffness and width along its length. It is this variation that enables the cochlea to vibrate at different locations in response to different frequencies. Higher frequency sounds cause vibrations nearer to the base of the cochlea, while lower frequency sounds affect areas further along the membrane. The length of the hairs on these sensory cells plays a crucial role in how they respond to particular frequencies, as they can bend in response to vibrations, sending signals to the brain that correspond to the specific frequency of the sound.

Other choices do not contribute directly to how the cochlea distinguishes sound frequencies. For instance, the shape of the eardrum and the position of the ossicles are significant for sound transmission, but they do not impact frequency discrimination within the cochlea itself. Similarly, the size of the ear canal may affect sound intensity but has no role in the detailed processing of frequency by the cochlea. Thus, the length of the hairs is the critical factor in allowing the cochlea to assign different frequencies of sound to their respective locations along the basilar membrane.