The auditory system is the toto[ of organs that translates an acoustical signal into the perception of a sound. An acoustic signal is a vibration. It is decribed by physical parameters. The perception of sound is the awareness of a signal being present and the attribution of certain qualities to this awareness. These qualities are called percepts. Examples of percepts are pitchr loudness and timbre. The percepts reflect the way in which the auditory system analyses and processes acoustic signals. Hence they also determine the most useful ways of describing the signals in physical terms. Frequency analysis is one of the most important processes involved in hearing. It is described in mathematical form by Fourier theory. This theory states that every repetitive signal can be described uniquely as a sum of sine waves. These sine waves are called frequency components. The elementary signal, therefore, consists of only one frequency component and is a sine-wave signal. The sine wave thus is also the elementary signal for our ear; we call the perception of this signal a pure tone. Signals consisting of more than one component are perceived as complex sounds.

G. van den Brink
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam