Auditory feature extraction using self-timed, continuous-time discrete-signal processing circuits

A compact integrated subsystem for accurate realtime measurement of level-crossing time-intervals, suitable for multiresolution feature extraction from an analog cochlear filter bank is presented. The subsystem is inspired by the function of the inner hair cells in the mammalian cochlea and is based on continuous-time discrete-signal processing circuits, Experimental results from a fabricated array of nine elements demonstrate instantaneous frequency-to-voltage conversion over a range covering the audio band, The power consumption is less than 20 mu W per cell from a 5-V supply, when the system is biased to operate over the speech frequency range.