Dynamics of spontaneous otoacoustic emissions

Spontaneous otoacoustic emissions (SOAEs) have become a hallmark feature in modern theories of an ‘active’ inner ear, given their numerous correlations to auditory function (e.g., threshold microstructure, neurophysiological tuning curves), near universality across tetrapod classes, and physiological correlates at the single hair cell level. However, while several different classes of nonlinear models exist that describe the mechanisms underlying SOAE generation (e.g., coupled limit-cycle oscillators, global standing waves), there is still disagreement as to precisely which biophysical concepts are at work. Such is further compounded by the idiosyncratic nature of SOAEs: Not all ears emit, and when present, SOAE activity can occur at seemingly arbitrary frequencies (though always within the most sensitive range of the audiogram) and in several forms (e.g., peaks, broad ‘baseline’ plateaus). The goal of the present study was to develop new signal processing and stimulation techniques that would allow for n...