Speech, music, and every other sound one hears can be described by the pattern of amplitude at different frequencies. This pattern, which is called the sound's spectrum, distinguishes one sound from others. In human speech, for example, the vowel in the word heat sounds different from the vowel in hat because amplitude peaks occur at different frequencies in the spectrum of the first vowel. Frequency analysis, described in this entry, refers to the ability to process different regions of the spectrum separately. This ability allows a person to discriminate two tones of different frequencies, but more importantly, it allows the locations of the amplitude peaks in the spectrum of any sound to be encoded and represented in the brain. Frequency analysis begins in the cochlea, ...