Fluctuation and correlation analyses for spontaneous otoacoustic activity from three terrestrial vertebrate groups

Abstract

Spontaneous otoacoustic emission (SOAE) is a telltale sign of an active ear that commonly manifest as a set of spectral peaks unique to a given individual. These sounds arise from a variety of species, despite dramatic morphological differences considered important for cochlear function. Furthermore, SOAE peaks exhibit amplitude (AM) and frequency modulations (FM), these fluctuations giving rise to their characteristic widths. There is, however, little consensus on how SOAE activity is generated. Here, we provide a systematic comparative study of SOAE peak fluctuations across three different groups: human, owl, and (anole) lizard. Specifically, we focus on analysis of correlative behavior in AM and FM fluctuations within a given peak (intra-peak, IrP) and across peaks (inter-peak, IPP) for SOAE waveforms measured from individual ears. In general, there were numerous similarities and differences across the three groups. To complement the empirical data, we also considered one model class (coupled limit cycle oscillators grouping into “frequency clusters”) to ascertain how well that model captures fluctuations and associated correlative relations. Initial results indicate the model shows some consistencies with data (e.g., IPP correlations strongest for nearest-neighboring peaks) but also inconsistencies (e.g., model commonly exhibits IPP-FM correlations and to a greater degree than AM).