The multiple-output cascade of asymmetric resonators with fast-acting compression (CARFAC) model of the auditory periphery combines concepts from many of the previous chapters, toward the primary goal of providing an efficient sound analyzer to support machine hearing applications.

An important secondary goal of CARFAC is to connect closely enough with known auditory physiology and psychophysics that it can be used to visualize and explain many interesting auditory phenomena. It is not a goal to be physically accurate, well calibrated, or in agreement with every detail of peripheral auditory processing, though it can be used as a starting point for those who have such goals.

Other than my own recent work (Lyon et al., 2010b; Lyon, 2010; Lyon et al., 2010a; Lyon, 2011b,a), the closest digital cochlear models in the literature to CARFAC are the variable-Q cascade–parallel models described by Kates (1993a), which also used cascades of asymmetric resonators specified by their poles and zeros; see the opening chapter quote above. The difference is that his stages include a second filter at each tap, and use a rather different pole–zero pattern, motivated by matching iso-rate neural tuning curves; ours is motivated by matching both psychophysical filters and physiological impulse responses, as discussed in Chapter 13.

Putting the Pieces Together

The CARFAC cochlear model pulls together the bits of knowledge that we surveyed in the previous nine chapters.

The coupled-form asymmetric resonators from Chapter 8 are combined into a filterbank with gammatone-like response as described in Chapter 9, using the cascade architecture motivated by Chapter 12.