Sources and Mechanisms of DPOAE Generation: Implications for the Prediction of Auditory Sensitivity

Abstract

Otoacoustic emissions (OAEs) have become a commonly used clinical tool for assessing cochlear health status, in particular, the integrity of the cochlear amplifier or motor component of cochlear function. Predicting hearing thresholds from OAEs, however, remains a research challenge. Models and experimental data suggest that there are two mechanisms involved in the generation of OAEs. For distortion product, transient, and high-level stimulus frequency emissions, the interaction of multiple sources of emissions in the cochlea leads to amplitude variation in the composite ear canal signal. Multiple sources of emissions complicate simple correlations between audiometric test frequencies and otoacoustic emission frequencies. Current research offers new methods for estimating the individual components of OAE generation. Input-output functions and DP-grams of the nonlinear component of the 2f2-f2 DPOAE may ultimately show better correlations with hearing thresholds. This paper reviews models of OAE generation and methods for estimating the contribution of source components to the composite emission that is recorded in the ear canal. The clinical implications of multiple source components are discussed.

Efeito da estimulação acústica contralateral nas medidas temporais das emissões otoacústicas

“…As EOAPD podem fornecer informações sobre frequências específicas com relação ao estado funcional da cóclea e dar uma noção da configuração audiomé-trica de um indivíduo 3 . O tempo de latência das EOAPD foi definido como o tempo em que o estímulo acústico leva para  de resposta na condição com ruído competitivo da condição sem ruído competitivo [7][8][9][10][11][12][13] .…”

Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

“…DPOAE slopes are generally lower than slopes estimated from TMCs and closer to physiological estimates from animals. At best, analysis of the relationship between DPOAE and basilar membrane inputoutput functions should be considered a qualitative assessment of accuracy because of possible influences of the interference between multiple generating sources of the DPOAE (and resulting fine structure in DPOAE responses), which is not optimal for assessment of basilar membrane compression (Shera and Guinan 1999;Shaffer et al 2003). In addition, although levels for L 1 and L 2 are typically set by the Kummer formula because it produces large DPOAE responses for normalhearing subjects, this approach may not be optimal for reflecting compression, especially for hearing-impaired subjects with reduced compression.…”

Otoacoustic Emission Theories and Behavioral Estimates of Human Basilar Membrane Motion Are Mutually Consistent

“…Furthermore, given that the behavioral and DPOAE optimal rules were inferred using fundamentally different assumptions and methods, the correspondence between the two provides further support for the assumptions of the behavioral TMC method, at least below 65 dB SPL. The level of the 2f 1 −f 2 DPOAE measured in the ear canal is almost certainly the sum of contributions from several cochlear sources and generation mechanisms (Shaffer et al 2003). These include distortion generated by nonlinear interaction of the primaries in the f 2 cochlear region (Martin et al 1998), reflection of this distortion at the 2f 1 −f 2 cochlear site (Kalluri and Shera 2001), and nonlinear interaction between f 2 and the first harmonic of f 1 (2f 1 ) at a more basal (2f 1 ) cochlear site (Fahey et al 2000).…”