The Auditory Filter Bank

It has been proposed that the peripheral auditory system effectively applies a filter bank to the acoustic signal reaching the ear drum. The output of this filter bank, consisting of the analysis signals $x_1(n), x_2(n), \ldots$, then affects the information transmitted to the auditory organs of the brain. In simulating the human auditory periphery, much scientific work to date thus employs some form of filter bank to emulate the characteristics of this proposed auditory bank. Some natural questions arise regarding this proposal:

• How many bands should an auditory filter bank have?
• What should the bandwidth of each band be?
• Should there be any overlap between adjacent bands?
• What should the bandwidths of each band be?

In the following sub-sections, we present the characteristics of two popular types of auditory filter banks: a more traditional, third-octave filter bank, and a more recently proposed Equivalent Rectangular Bandwidth (ERB) filter bank.