Average optimal DPOAE primary tone levels in normal-hearing adults

A clinical comparison of DPOAE fine structure reduction methods

OBJECTIVE

To evaluate two real-time methods for reducing distortion product otoacoustic emission (DPOAE) fine structure in terms of DPOAE amplitude and fine structure depth.

DESIGN

A prospective, repeated-measures design was used to assess DPOAE characteristics in response to a conventional stimulation method (Conv.), as well as for methods implementing either a generic suppressor tone (Supp.) or frequency modulation of the f₂ primary tone (FM).

STUDY SAMPLE

Eighty-three young adults (58 females) between the ages of 20 and 34 years with normal hearing completed testing for this study.

RESULTS

Use of the Conv. and FM methods resulted in consistently higher DPOAE levels relative to the Supp. method, with average advantages of 6 and 5 dB, respectively. For all methods, increased fine structure depth was observed for stimulation with lower level (25-45 dB SPL) and lower frequency (1000-3000 Hz) primary tones. Finally, use of the Supp. and FM methods resulted in significantly decreased fine structure depth relative to the Conv. method.

CONCLUSION

Through frequency modulation of the f₂ primary tone, it was possible to reduce the depth of fine structure across a clinically meaningful range of stimulation levels and frequencies without concomitant reduction in DPOAE amplitude.

Subclinical conductive hearing loss significantly reduces otoacoustic emission amplitude: Implications for test performance

OBJECTIVES

Distortion product otoacoustic emissions (DPOAEs) are a time-efficient, non-invasive means of assessing the integrity of active inner ear mechanics. Unfortunately, the presence of even relatively minor conductive hearing loss (CHL) has been suggested to reduce the clinical utility of DPOAEs significantly. The primary aims of this study were to systematically evaluate the impact of CHL on DPOAE amplitude and to determine if ear-specific primary tone level manipulations can be used to mitigate CHL impact and recover DPOAE measurability.

METHODS

For 30 young adults (57 ears) with normal hearing, DPOAEs were obtained for f₂ = 1-6 kHz. Observed DPOAE amplitudes were used to generate ear- and frequency-specific models with the primary tone levels, L₁ and L_2, as inputs and predicted DPOAE amplitude, L_DP, as output. These models were then used to simulate the effect of CHL (0-15 dB), as well as L₁ manipulations (0-15 dB), on DPOAE measurability.

RESULTS

Mean L_DP for every CHL condition was significantly different from that for all other conditions (p = <.001), with a mean L_DP attenuation of 8.7 dB for every 5 dB increase in CHL. Mean DPOAE measurability in response to a standard clinical stimulation paradigm of L₁/L₂ = 65/55 (dB SPL) was determined to be 99%, 84%, 37%, and 9% in the presence of 0, 5, 10, and 15 dB CHL, respectively. In the presence of 10 dB CHL, altering L₁ resulted in an approximately 25% increase in DPOAE responses.

CONCLUSION

Subclinical CHL loss is sufficient to significantly impair DPOAE measurability in a meaningful proportion of otherwise healthy ears. However, through strategic alteration of primary tone levels, the clinician can mitigate CHL impact and at least partially recover DPOAE measurability.

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.

Wideband Absorbance and 226-Hz Tympanometry in the Prediction of Optimal Distortion Product Otoacoustic Emission Primary Tone Levels

PURPOSE

Distortion product otoacoustic emission (DPOAE) amplitude is sensitive to the primary tone level separation effective within the cochlea. Despite potential for middle ear sound transmission characteristics to affect this separation, no primary tone level optimization formula accounts for its influence. This study was conducted to determine if inclusion of ear- and frequency-specific immittance features improves primary tone level optimization formula performance beyond that achieved using a univariate, L2-based formula.

METHOD

For 30 adults with normal hearing, DPOAE, wideband absorbance, and 226-Hz tympanometry measures were completed. A mixed linear modeling technique, incorporating both primary tone and acoustic immittance features, was used to generate a multivariable formula for the middle ear-specific recommendation of primary tone level separations for f2 = 1-6 kHz. The accuracy with which L1OPT, or the L1 observed to maximize DPOAE level for each given L2, could be predicted using the multivariable formula was then compared with that of a traditional, L2-based univariate formula for each individual ear.

RESULTS

Use of the multivariable formula L1 = 0.47L2 + 2.40A + f2param + 38 [dB SPL] resulted in significantly more accurate L1OPT predictions than did the univariate formula L1 = 0.49L2 + 41 [dB SPL]. Although average improvement was small, meaningful improvements were identified within individual ears, especially for f2 = 1 and 6 kHz.

CONCLUSION

Incorporation of a wideband absorbance measure into a primary tone level optimization formula resulted in a minor average improvement in L1OPT prediction accuracy when compared with a traditional univariate optimization formula. Further research is needed to identify characteristics of ears that might disproportionately benefit from the additional measure.

A systematic review of stimulus parameters for eliciting distortion product otoacoustic emissions from adult humans

OBJECTIVE

The objective of this study is to review the scientific literature to determine if a set of stimulus parameters can be described to elicit distortion product otoacoustic emissions (DPOAEs) of higher absolute level and/or greater reliability in healthy adult humans and higher sensitivity and specificity in adults with cochlear lesions.

DESIGN

Systematic review.

STUDY SAMPLE

Searches of four electronic databases yielded 47 studies that had used different parameters to elicit DPOAEs from within or between-groups of adult humans.

RESULTS

The wide range of stimulus parameters used in the reviewed studies saw a wide range of reported values for DPOAE level, reliability, and sensitivity and specificity to cochlear lesions.

CONCLUSION

The most commonly used stimulus parameters for eliciting DPOAEs from adult humans have included frequency ratios for the two primary tones (f₂/f₁) of between 1.04 and 1.4 and levels (L₁/L₂) of 65/55 dB SPL. The most commonly used parameters for eliciting DPOAEs of higher level in healthy adults appear to be linked to f₂/f₁ values between 1.20 and 1.22 and L₁/L₂ levels of 75/75 dB SPL. The stimulus parameters for eliciting DPOAEs of greater reliability in healthy adults and higher sensitivity and specificity in adults with cochlear lesions have yet to be clearly determined.