Modelling the Ear with Electronic Oscillators: The Wien Bridge Oscillator as a Physical Analogue for the Hair Cell

The hair cell is the sensory organ of the human ear. In the vestibule, hair cells allow us to detect linear accelerations and rotations of the head. In the cochlea, patterns of hair cell activation along the dynamic basilar membrane allow us to encode information about complex sounds such as speech and music. A particularly important feature of hair cells is their intrinsic nonlinearity which gives rise to both a quiescent and oscillatory regime. This nonlinearity has been approached in the literature by treating the hair cell as a Hopf-type oscillator, wherein cochlear hair cells are poised just below the bifurcation point. In our research, we sought to construct and model a simple physical system that exhibited this same Hopf-type nonlinearity. We chose as our model system the Wien bridge electronic oscillator, an affordable and relatively simple circuit which mimics many of the essential features of the hair cell. We will introduce our theoretical model for nonlinearity and resonance within the Wien bridge oscillator based on experimental results, and discuss parallels between the dynamics of the Wien bridge oscillator and the dynamics of the hair cell.