Comparing external tympanum vibration and spontaneous otoacoustic emissions

Bergevin, Christopher; Mhatre, Natasha; Mason, Andrew C.

doi:10.1063/1.5038519

Cited by 2 publications

(1 citation statement)

References 15 publications

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“…Because the coupler changes the acoustic-impedance load on the ear, the SOAE spectrum is expected to differ from that of an unenclosed ear. Most SOAE peaks should increase with decreasing coupler volume and might shift in frequency, as evidenced by comparisons with spontaneous eardrum vibrations ( 31 ).…”

Section: Methodsmentioning

confidence: 99%

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

Roongthumskul

Maoiléidigh

Hudspeth

2019

Biophysical Journal

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Spontaneous otoacoustic emissions (SOAEs) are weak sounds that emanate from the ears of tetrapods in the absence of acoustic stimulation. These emissions are an epiphenomenon of the inner ear's active process, which enhances the auditory system’s sensitivity to weak sounds, but their mechanism of production remains a matter of debate. We recorded SOAEs simultaneously from the two ears of the tokay gecko and found that binaural emissions could be strongly correlated: some emissions occurred at the same frequency in both ears and were highly synchronized. Suppression of the emissions in one ear often changed the amplitude or shifted the frequency of emissions in the other. Decreasing the frequency of emissions from one ear by lowering its temperature usually reduced the frequency of the contralateral emissions. To understand the relationship between binaural SOAEs, we developed a mathematical model of the eardrums as noisy nonlinear oscillators coupled by the air within an animal’s mouth. By according with the model, the results indicate that some SOAEs are generated bilaterally through acoustic coupling across the oral cavity. The model predicts that sound localization through the acoustic coupling between ears is influenced by the active processes of both ears.

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Section: Methodsmentioning

confidence: 99%

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

Roongthumskul

Maoiléidigh

Hudspeth

2019

Biophysical Journal

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Auditory Cellular Cooperativity Probed Via Spontaneous Otoacoustic Emissions

Bergevin,

Whiley,

Wit

et al. 2024

Preprint

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As a sound pressure detector that uses energy to boost both its sensitivity and selectivity, the inner ear is an active non-equilibrium system. The collective processes of the inner ear giving rise to this exquisite functionality remain poorly understood. One manifestation of the active ear across the animal kingdom is the presence of spontaneous otoacoustic emission (SOAE), idiosyncratic arrays of spectral peaks that can be measured using a sensitive microphone in the ear canal.1 Current SOAE models attempt to explain how multiple peaks arise, and generally assume a spatially-distributed tonotopic system. However, the nature of the generators, their coupling, and the role of noise (e.g., Brownian motion) are hotly debated, especially given the inner ear morphological diversity across vertebrates. One means of probing these facets of emission generation is studying fluctuations in SOAE peak properties, which produce amplitude (AM) and frequency modulations (FM). These properties are likely related to the presence of noise affecting active cellular generation elements, and the coupling between generators. To better biophysically constrain models, this study characterizes the fluctuations in filtered SOAE peak waveforms, focusing on interrelations within and across peaks. A systematic approach is taken, examining three species that exhibit disparate inner ear morphologies: humans, barn owls, and green anole lizards. To varying degrees across all three groups, SOAE peaks have intra-(IrP) and interpeak (IPP) correlations indicative of interactions between generative elements. Activity from anole lizards, whose auditory sensory organ is relatively much smaller than that of humans or barn owls, showed a much higher incidence of IPP correlations. Taken together, we propose that these data are indicative of SOAE cellular generators acting cooperatively, allowing the ear to function as an optimized detector.Significance StatementThe inner ear is a complex biomechanical system whose function is not well understood. To further elucidate the role of coupling in emission generation, this study systematically compares fluctuations in sound emitted spontaneously from the ear (spontaneous otoacoustic emission, SOAE) across three vertebrates. Ultimately these data serve to illustrate that the inner ear is a non-equilibrium, active system whose cellular elements work cooperatively. A clearer understanding of SOAE generation and how it manifests across the animal kingdom will significantly advance our understanding of both normal and impaired auditory function.

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Comparing external tympanum vibration and spontaneous otoacoustic emissions

Cited by 2 publications

References 15 publications

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

Auditory Cellular Cooperativity Probed Via Spontaneous Otoacoustic Emissions

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