Mimicking cochlear pre-processing using critically coupled MEMS sensors

The characteristic of our hearing is essentially based on the mechanics in our inner ear. Around 3000 hair cells in the cochlea decode vibrations into electrical signals, covering frequencies from 0.020–20 kHz with relative resolutions normalized by their natural frequency of 0.1%–0.4% and a high dynamic range of 0–120 dB. These dynamic properties can be described by critical oscillators as they provide high resolution and nonlinear response near their critical points. However, the wide frequency range cannot be achieved as high sensitivity requires high Q -factors and is therefore associated with narrow frequency range. To overcome this, frequency tunability could be used to increase the detectable frequency range while maintaining high sensitivity. One solution to achieve frequency tuning is the mutual coupling of oscillators. To this end, a bio-inspired sensing system based on coupled resonators tuned near their critical points is presented, whose frequency can be tuned by varying the feedback of the individual resonator. In the coupled system three Andronov–Hopf bifurcations are identified, where two of them enable frequency tunability. We show that this adaptability of the frequency enables the coverage of a wide frequency range with limited number of resonators and yet preserves a high resolution with low number of resonators, which make them suitable for hardware implementation.