The Ear

The function of the two ears is to convert acoustic information picked up by the pinnas to neural information that can used by the central auditory system to interpret the incoming sounds in terms of what happens around the listener, where it happens, and in what environment it happens. This process starts in the outer ears, which concentrate the acoustic energy of the sound waves at the tympanic membranes that start vibrating. This in turn sets the ossicles within the middle ear in motion which transfer the acoustic energy to the fluid filled inner ear. There, the acoustic energy is distributed over a large number of overlapping auditory bandpass filters. These auditory filters perform a complex transduction process in which weak frequency components are amplified and mechanical movements are converted into trains of electrical pulses, called spikes or action potentials. These spike trains contain all information used by the central nervous system to carry out its function of interpreting the auditory environment. A description is presented in terms of the spectral and temporal properties of the incoming sounds encoded by these trains of action potentials.