Summary
This research work is centred around coupling nonlinear resonators for bio-inspired acoustic sensing to improve sound processing and thus close the performance gap to human hearing. Critical oscillators tuned near a Hopf bifurcation were shown to model part of the remarkable functionalities of human hearing, i.e. a large dynamic range, a high frequency resolution, and improved signal-to-noise ratios. Sensors built on this concept exhibit high quality factors i.e. high gain and small bandwidth, due to the nonlinear and resonant operation principle. However, to cover the audible frequency range, a high amount of sensors would be required. Thus, we explore how coupling of nonlinear resonators can overcome this issue. Our nonlinear resonators are silicon cantilevers combined with an electronic feedback. Diffusive, output-signal based coupling is implemented using the difference between the sensing signals of two resonators as their driving signal. Combining experiments and simulations of two coupled resonators, we show that depending on the polarity of the coupling two bifurcation points with different sensing properties are obtained. Near one bifurcation point a dampened response of both resonators to sound is observed. Close to the other bifurcation point a strong increase in gain and a nonlinear response is obtained. Finally, Results from extending the system to a chain of four resonators will be discussed.
