Analyzing Stimulus-frequency Otoacoustic Emission Fine Structure Using an Additive Model

A good understanding of the origin of stimulus-frequency otoacoustic emission (SFOAE) fine structure in human ears and its probe level-dependency has potential clinical significance. In this study, we develop a two-component additive model, with total SFOAE unmixed into short- and long-latency components (or reflections) using time windowing method, to investigate the origin of SFOAE fine structure in humans from 40 to 70 dB SPL. The two-component additive model predicts that a spectral notch seen in the amplitude fine structure is produced when short- and long-latency components have opposite phases and comparable magnitudes. And the depth of spectral notch is significantly correlated with the amplitude difference between the two separated components, as well as their degree of opposite phase. Our independent evidence for components contributing to SFOAE fine structure suggests that amplitude, phase and delay fine structure in the human SFOAEs are a construct of the complex addition of two or more internal reflections with different phase slops in the cochlea.