Output encoding for cochlear signal analysis

The biological inner ear, or cochlea, is an amazing sensor that performs auditory frequency analysis over an ultra-broadband frequency range of ~20 Hz to 20 kHz with exquisite sensitivity and high energy efficiency. Electronic cochlear models, which mimic the exponentially-tapered structure of the biological inner ear using transmission lines or filter cascades, have been shown to be fast and extremely efficient spectrum analyzers at both audio and radio frequencies (RF). Here we present improved output encoding methods for such cochlea-like analyzers. We have developed neuron-like asynchronous event-generation circuits to efficiently encode cochlear outputs, including ring-oscillator-based injection-locked frequency dividers (ILFDs) that accurately encode input frequencies and phase-sensitive detectors that encode both amplitude and phase information and thereby improve frequency resolution without reducing temporal resolution.