Live demonstration: The self-tuned regenerative electromechanical parametric amplifier

We have designed, constructed and tested an electromechanical acoustic sensor as a conceptual model for the active process in the mammalian cochlea. The sensor is based on a mechanical resonator - a stretched latex band - which is tonically (tensionally) modulated by an electromechanical actuator. A feedback circuit senses the motion of the resonator, and modulates its tension at twice the frequency of its motion. An amplifier is thereby formed, which is self-tuned to the circuit´s resonance, and which produces gain by regeneration and degenerate parametric pumping. The system is simple in structure; physiologically plausible as a model for the basilar membrane and associated hair cells; and reproduces several well-known features of the cochlear amplifier.