Negative Middle Ear Pressure and Composite and Component Distortion Product Otoacoustic Emissions

The Effect of Stimuli Level on Distortion Product Otoacoustic Emission in Normal Hearing Adults

The goal of this study is to compare three of the most commonly used primary-level relation paradigms (i.e., Scissors, Boys Town 'Optimal', and Equal-Level) in generation of distortion product otoacoustic emissions (DPOAEs) in normal hearing adults. The generator and reflection components were extracted from DPOAEs in each paradigm. The generator and reflection component levels and input/output (I/O) functions were compared across paradigms and primary-tone levels. The results showed a different I/O function growth behavior across frequency and levels among paradigms. The Optimal paradigm showed a systematic change in the generator and reflection component levels and I/O slopes across primary levels among subjects. Moreover, the levels and slopes in the Optimal paradigm were more distinct across levels with less variations across frequency leading to a systematic change in the DPOAE fine structure across levels. The I/O functions were found to be more sensitive to the selected paradigm; especially the I/O function for the reflection component. The I/O functions of the reflection components showed large variability across frequencies due to different frequency shifts in their microstructure depending on the paradigm. The findings of this study suggested the Optimal paradigm as the proper primary-level relation to study cochlear amplification/compression. The findings of this study shows that care needs to be taken in comparing the findings of different studies that generated DPOAEs with a different level-relation paradigm.

Effect of chronic suppurative otitis media on distortion product otoacoustic emission input-output functions in conventional and ultra-high frequencies

BACKGROUND

Detection and valid measurements of distortion product otoacoustic emissions are not influenced by cochlear status alone, but also by middle-ear status. There is a need to understand the use of ultra-high frequency distortion product otoacoustic emissions in cases of abnormal distortion product otoacoustic emission findings for conventional frequencies related to the middle-ear condition.

METHOD

The present study investigated distortion product otoacoustic emission input-output functions in conventional and ultra-high frequencies in: 37 adults with chronic suppurative otitis media (clinical group) and 37 adults with normal hearing sensitivity (control group).

RESULTS

There were significant reductions in distortion product otoacoustic emission amplitude and mean signal-to-noise ratio in the clinical group compared to the control group, especially for conventional frequencies.

CONCLUSION

There was a significant reduction in the rate of ears with measurable distortion product otoacoustic emissions in the clinical group, especially for conventional frequencies. The effect of chronic suppurative otitis media was more pronounced in the conventional frequency range compared to the smaller effect seen in the ultra-high frequency range.

Contrasting Effects of Pressure Compensation on TEOAE and DPOAE in Children With Negative Middle Ear Pressure

In children with normal cochlear acuity, middle ear fluid often abolishes otoacoustic emissions (OAEs), and negative middle ear pressure (NMEP) reduces them. No convincing evidence of beneficial pressure compensation on distortion product OAE (DPOAE) has yet been presented. Two studies aimed to document effects of NMEP on transient OAE (TEOAE) and DPOAE. In Study 1, TEOAE and DPOAE pass/fail responses were analyzed before and after pressure compensation in 50 consecutive qualifying referrals having NMEP from -100 to -299 daPa. Study 2 concentrated on DPOAE, recording both amplitude (distortion product amplitude) and signal-to-noise ratio (SNR) before and after pressure compensation. Of the 20 participants, 5 had both ears qualifying. An effect of compensation on meeting a pass criterion was present in TEOAE for both left and right ear data in Study 1 but not demonstrable in DPOAE. In Study 2, the distortion product amplitude compensation effect was marginal overall, and depended on recording frequency band. SNR values improved moderately after pressure compensation in the two (overlapping) sets of single-ear data. In the five cases with both ears qualifying, a stronger compensation effect size, over 3 dB, was seen. The absolute dependence of SNR on frequency was also strongly replicated, but in no analysis, the frequency × compensation interaction was significant. Independent of particular frequency range, the data support a limited SNR improvement in 2 to 3 dB for compensation in DPOAE, with slightly larger effects in ears giving SNRs between 0 dB and +6 dB, where pass/fail cutoffs would generally be located.

Effects of Negative Middle Ear Pressure on Wideband Acoustic Immittance in Normal-Hearing Adults

OBJECTIVES

Wideband acoustic immittance (WAI) measurements are capable of quantifying middle ear performance over a wide range of frequencies relevant to human hearing. Static pressure in the middle ear cavity affects sound transmission to the cochlea, but few datasets exist to quantify the relationship between middle ear transmission and the static pressure. In this study, WAI measurements of normal ears are analyzed in both negative middle ear pressure (NMEP) and ambient middle ear pressure (AMEP) conditions, with a focus on the effects of NMEP in individual ears.

DESIGN

Eight subjects with normal middle ear function were trained to induce consistent NMEPs, quantified by the tympanic peak pressure (TPP) and WAI. The effects of NMEP on the wideband power absorbance level are analyzed for individual ears. Complex (magnitude and phase) WAI quantities at the tympanic membrane (TM) are studied by removing the delay due to the residual ear canal (REC) volume between the probe tip and the TM. WAI results are then analyzed using a simplified classical model of the middle ear.

RESULTS

For the 8 ears presented here, NMEP has the largest and most significant effect across ears from 0.8 to 1.9 kHz, resulting in reduced power absorbance by the middle ear and cochlea. On average, NMEP causes a decrease in the power absorbance level for low- to mid-frequencies, and a small increase above about 4 kHz. The effects of NMEP on WAI quantities, including the absorbance level and TM impedance, vary considerably across ears. The complex WAI at the TM and fitted model parameters show that NMEP causes a decrease in the aggregate compliance at the TM. Estimated REC delays show little to no dependence on NMEP.

CONCLUSIONS

In agreement with previous results, these data show that the power absorbance level is most sensitive to NMEP around 1 kHz. The REC effect is removed from WAI measurements, allowing for direct estimation of complex WAI at the TM. These estimates show NMEP effects consistent with an increased stiffness in the middle ear, which could originate from the TM, tensor tympani, annular ligament, or other middle ear structures. Model results quantify this nonlinear, stiffness-related change in a systematic way, that is not dependent on averaging WAI results in frequency bands. Given the variability of pressure effects, likely related to intersubject variability at AMEP, TPP is not a strong predictor of change in WAI at the TM. More data and modeling will be needed to better quantify the relationship between NMEP, WAI, and middle ear transmission.

Frequency-change in DPOAE evoked by 1 s/octave sweeping primaries in newborns and adults

Distortion product otoacoustic emissions (DPOAE) in newborns and adults were evoked by sweeping primaries up and down in frequency at 1 s/octave. Sweeping up and down in frequency resulted in changes in the amplitude vs. frequency functions of the composite DPOAE and its two major components. In addition, DPOAE component phases differed slightly between the up- and down-swept conditions. The changes in amplitude vs. frequency functions were quantified using a covariate correlation technique, yielding single-valued estimates of the magnitude of the frequency changes. Separate analyses were performed for the entire DPOAE frequency range and split into low and high frequency ranges. There were consistent changes in newborn and adult composite DPOAEs and reflection components, but not generator components. Adults had significant frequency changes in the composite DPOAE for all frequency ranges and in the reflection component for the entire frequency range. Newborns had significant frequency change in the reflection component for all frequency ranges. Differences in frequency change between adults and newborns may stem from developmental changes in cochlear processing. Alignment of the component phase differences between the up- and down-swept conditions resulted in elimination of frequency-change in reconstructed composite DPOAEs.