Other Papers
A Clinically Viable Medial Olivocochlear Reflex Assay Using Transient-Evoked Otoacoustic Emissions. by Lapsley Miller, J. A., Reed, C. M., Marshall, L., Perez, Z. D., and Villabona, T. (2023). Ear Hear., Online Ahead of Print.
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OBJECTIVES: The contralateral medial olivocochlear reflex (MOCR) strength may indicate various auditory conditions in humans, but a clinically viable assay and equipment are needed for quick, accurate, and reliable measurements. The first experiment compared an earlier version of the assay, which used a nonlinear-mode chirp stimulus, with a new assay using a linear-mode click stimulus, designed to give reliable MOCR measurements in most normal-hearing ears. The second experiment extended the improved assay on a purpose-built binaural hardware platform that used forward-pressure level (FPL) calibration for both the stimulus and the contralateral MOCR elicitor. DESIGN: Transient-evoked otoacoustic emission (TEOAE) tests were measured with and without a 60-dB SPL MOCR-evoking contralateral broadband noise. The normalized MOCR strength (MOCR%) was derived from the TEOAE responses for each trial pair using the complex pressure difference weighted by the TEOAE magnitude. Experiment 1 compared MOCR% within-subject and across-day using two TEOAE stimuli: nonlinear-mode chirps (50 dB SPL, bandpass 1-5 kHz, 14 ms window delayed by 2 ms) and linear-mode clicks (50 dB SPL, bandpass 0.5-2.5 kHz, 13 ms window delayed by 5 ms). TEOAE responses were analyzed in the 0.5 to 2.5 kHz band. Thirty adult participants with normal hearing (30 ears) completed the study. The TEOAE stimulus was calibrated in situ using spectral flattening, and the contralateral noise was calibrated in a coupler. Twelve TEOAE trial pairs were collected for each participant and condition. Experiment 2 used a purpose-built binaural system. The TEOAE stimuli were linear-mode clicks (50 dB SPL, bandpass 1-3 kHz, 13 ms window delayed by 5 ms), analyzed in the 1 to 3 kHz band over ~12 trial pairs. After a probe refit, an additional trial pair was collected for the two early-stopping signal-to-noise ratio criteria (15 and 20 dB). They were evaluated for single-trial reliability and test time. Nineteen adult participants with normal hearing (38 ears) completed the study. The TEOAE clicks and contralateral elicitor noise were calibrated in situ using FPL and delivered with automated timing. RESULTS: MOCR% for linear-mode clicks was distinguishable from measurement variability in 98% to 100% of participants' ears (both experiments), compared with only 73% for the nonlinear-mode chirp (experiment 1). MOCR detectability was assessed using the MOCR% across-subject/within-subject variance ratio. The ratio in experiment 1 for linear-mode clicks was higher (8.0) than for nonlinear-mode chirps (6.4). The ratio for linear-mode clicks (8.9) in experiment 2 was slightly higher than for the comparable linear-mode stimulus (8.0) in experiment 1. TEOAEs showed excellent reliability with high signal-to-noise ratios in both experiments, but reliability was higher for linear-mode clicks than nonlinear-mode chirps. MOCR reliability for the two stimuli was comparable. The FPL pressure response retest reliability derived from the SPL at the microphone was higher than the SPL retest reliability across 0.4 to 8 kHz. Stable results required 2 to 3 trial pairs for the linear-mode click (experiments 1 and 2) and three for the nonlinear-mode chirp (experiment 1), taking around 2 min on average. CONCLUSIONS: The linear-mode click assay produced measurable, reliable, and stable TEOAE and MOCR results on both hardware platforms in around 2 min per ear. The stimulus design and response window ensured that any stimulus artifact in linear mode was unlikely to confound the results. The refined assay is ready to produce high-quality data quickly for clinical and field studies to develop population norms, recognize diagnostic patterns, and determine risk profiles.
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Pure-Tone Audiometry With Forward Pressure Level Calibration Leads to Clinically-Relevant Improvements in Test-Retest Reliability. by Lapsley Miller, J. A., Reed, C. M., Robinson, S. R., and Perez, Z. D. (2018). Ear Hear., 39(5), 946-957.
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OBJECTIVES: Clinical pure-tone audiometry is conducted using stimuli delivered through supra-aural headphones or insert earphones. The stimuli are calibrated in an acoustic (average ear) coupler. Deviations in individual-ear acoustics from the coupler acoustics affect test validity, and variations in probe insertion and headphone placement affect both test validity and test-retest reliability. Using an insert earphone designed for otoacoustic emission testing, which contains a microphone and loudspeaker, an individualized in-the-ear calibration can be calculated from the ear-canal sound pressure measured at the microphone. However, the total sound pressure level (SPL) measured at the microphone may be affected by standing-wave nulls at higher frequencies, producing errors in stimulus level of up to 20 dB. An alternative is to calibrate using the forward pressure level (FPL) component, which is derived from the total SPL using a wideband acoustic immittance measurement, and represents the pressure wave incident on the eardrum. The objective of this study is to establish test-retest reliability for FPL calibration of pure-tone audiometry stimuli, compared with in-the-ear and coupler sound pressure calibrations. DESIGN: The authors compared standard audiometry using a modern clinical audiometer with TDH-39P supra-aural headphones calibrated in a coupler to a prototype audiometer with an ER10C earphone calibrated three ways: (1) in-the-ear using the total SPL at the microphone, (2) in-the-ear using the FPL at the microphone, and (3) in a coupler (all three are derived from the same measurement). The test procedure was similar to that commonly used in hearing-conservation programs, using pulsed-tone test frequencies at 0.5, 1, 2, 3, 4, 6, and 8 kHz, and an automated modified Hughson-Westlake audiometric procedure. Fifteen adult human participants with normal to mildly-impaired hearing were selected, and one ear from each was tested. Participants completed 10 audiograms on each system, with test-order randomly varied and with headphones and earphones refitted by the tester between tests. RESULTS: Fourteen of 15 ears had standing-wave nulls present between 4 and 8 kHz. The mean intrasubject SD at 6 and 8 kHz was lowest for the FPL calibration, and was comparable with the low-frequency reliability across calibration methods. This decrease in variability translates to statistically-derived significant threshold shift criteria indicating that 15 dB shifts in hearing can be reliably detected at 6 and 8 kHz using FPL-calibrated ER10C earphones, compared with 20 to 25 dB shifts using standard TDH-39P headphones with a coupler calibration. CONCLUSIONS: These results indicate that reliability is better with insert earphones, especially with in-the-ear FPL calibration, compared with a standard clinical audiometer with supra-aural headphones. However, in-the-ear SPL calibration should not be used due to its sensitivity to standing waves. The improvement in reliability is clinically meaningful, potentially allowing hearing-conservation programs to more confidently determine significant threshold shifts at 6 kHz-a key frequency for the early detection of noise-induced hearing loss.
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The clinical utility of expressing hearing thresholds in terms of the forward-going sound pressure wave. by Withnell, R. H., Jeng, P. S., Parent, P., and Levitt, H. (2014). Int J. Audiol, 53, 522-530.
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OBJECTIVE: To assess the clinical utility of quantifying pure-tone hearing thresholds in terms of the forward-going sound pressure wave. DESIGN: Sound pressure measurements in the ear canal were used to derive, with hearing threshold measurements, hearing thresholds expressed in terms of the forward-going sound pressure wave, hearing thresholds based on coupler-based calibration, and hearing thresholds expressed in terms of the sound pressure measured at the microphone. STUDY SAMPLE: Fifty-two adults, 18 to 34 years of age, served as the study group. RESULTS: Audiogram configurations were similar up to 2000 Hz for the three expressions of hearing threshold, consistent with the ear canal acting as a simple volume up to this frequency. Above 2000 Hz, notable differences in hearing threshold were found, consistent with the acoustic input impedance of the ear differing from a rigid, hard-walled cavity. Repeat testing showed all three expressions of hearing threshold to be repeatable. High density measurements of hearing threshold from 3000 to 6000 Hz provided qualified support for the derivation of the forward-going sound pressure wave. CONCLUSIONS: Hearing thresholds expressed in terms of the forward-going sound pressure wave are repeatable, and with in-situ calibration, may be superior to the current coupler-based method.
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Effect of Calibration Method on Distortion-Product Otoacoustic Emission Measurements at and Around 4 kHz. by Reuven, M. L., Neely, S. T., Kopun, J. G., Rasetshwane, D. M., Allen, J. B., Tan, H., & Gorga, M. P. (2013). Ear Hear, 34(6), 779-788.
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OBJECTIVES: Distortion-product otoacoustic emissions (DPOAEs) collected after sound pressure level (SPL) calibration are susceptible to standing waves that affect measurements at the plane of the probe microphone due to overlap of incident and reflected waves. These standing-wave effects can be as large as 20 dB, and may affect frequencies both above and below 4 kHz. It has been shown that forward pressure level (FPL) calibration minimizes standing-wave effects by isolating the forward-propagating component of the stimulus. Yet, previous work has failed to demonstrate more than a small difference in test performance and behavioral-threshold prediction with DPOAEs after SPL and FPL calibration. One potential limitation in prior studies is that measurements were restricted to octave and interoctave frequencies; as a consequence, data were not necessarily collected at the standing-wave null frequency. In the present study, DPOAE responses were measured with f2 set to each participant's standing-wave frequency in an effort to increase the possibility that differences in test performance and threshold prediction would be observed for SPL and FPL calibration methods. DESIGN: Data were collected from 42 normal-hearing participants and 93 participants with hearing loss. DPOAEs were measured with f2 set to 4 kHz and at each participant's notch frequency after SPL and FPL calibration. DPOAE input/output functions were obtained from -10 to 80 dB in 5 dB steps for each calibration/stimulus condition. Test performance was evaluated using clinical decision theory. Both area under receiver operating characteristic curves for all stimulus levels and cumulative distributions when L2 = 50 dB (a level at which the best performance was observed regardless of calibration method) were used to evaluate the accuracy with which auditory status was determined. A bootstrap procedure was used to evaluate the significance of the differences in test performance between SPL and FPL calibrations. DPOAE predictions of behavioral threshold were evaluated by correlating actual behavioral thresholds and predicted thresholds using a multiple linear regression model. RESULTS: First, larger DPOAE levels were measured after SPL calibration than after FPL calibration, which demonstrated the expected impact of standing waves. Second, for both FPL and SPL calibration, test performance was best for moderate stimulus levels. Third, differences in test performance between calibration methods were evident at low- and high-stimulus levels. Fourth, there were small but statistically significant improvements in test performance after FPL calibration for clinically relevant conditions. Fifth, calibration method had no effect on threshold prediction. CONCLUSIONS: Standing waves after SPL calibration have an impact on DPOAE levels. Although the effect of calibration method on test performance was small, test performance was better after FPL calibration than after SPL calibration. There was no effect of calibration method on predictions of behavioral threshold.
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Investigation of bacterial biofilm in the human middle ear using optical coherence tomography and acoustic measurements. by Nguyen, C. T., Robinson, S. R., Jung, W., Novak, M. A., Boppart, S. A., and Allen, J. B. (2013) Hearing Research, 301, 193-200.
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Children with chronic otitis media (OM) often have conductive hearing loss which results in communication difficulties and requires surgical treatment. Recent studies have provided clinical evidence that there is a one-to-one correspondence between chronic OM and the presence of a bacterial biofilm behind the tympanic membrane (TM). Here we investigate the acoustic effects of bacterial biofilms, confirmed using optical coherence tomography (OCT), in adult ears. Non-invasive OCT images are collected to visualize the cross-sectional structure of the middle ear, verifying the presence of a biofilm behind the TM. Wideband measurements of acoustic reflectance and impedance (0.2e6 [kHz]) are used to study the acoustic properties of ears with confirmed bacterial biofilms. Compared to known acoustic properties of normal middle ears, each of the ears with a bacterial biofilm has an elevated power reflectance in the 1 to 3 [kHz] range, corresponding to an abnormally small resistance (real part of the impedance). These results provide assistance for the clinical diagnosis of a bacterial biofilm, which could lead to improved treatment of chronic middle ear infection and further understanding of the impact of chronic OM on conductive hearing loss.
This article is part of a Special Issue entitled “MEMRO 2012”
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Characterizing the ear canal acoustic impedance and reflectance by pole-zero fitting. by Robinson, S., Nguyen, C., and Allen, J. B. Hearing Research 301, 168-182 (2013).
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This study characterizes middle ear complex acoustic reflectance (CAR) and impedance by fitting poles and zeros to real-ear measurements. The goal of this work is to establish a quantitative connection between pole-zero locations and the underlying physical properties of CAR data. Most previous studies have analyzed CAR magnitude; while the magnitude accounts for reflected power, it does not encode latency information. Thus, an analysis that studies the real and imaginary parts of the data together, being more general, should be more powerful. Pole-zero fitting of CAR data is examined using data compiled from various studies, dating back to Voss and Allen (1994). Recent CAR measurements were taken using the Mimosa Acoustics HearID system, which makes complex acoustic impedance and reflectance measurements in the ear canal over a 0.2–6.0 [kHz] frequency range. Pole-zero fits to measurements over this range are achieved with an average RMS relative error of less than 3% with 12 poles. Factoring the reflectance fit into its all-pass and minimum-phase components estimates the effect of the residual ear canal, allowing for comparison of the eardrum impedance and admittance across measurements. It was found that individual CAR magnitude variations for normal middle ears in the 1–4 [kHz] range often give rise to closely-placed pole-zero pairs, and that the locations of the poles and zeros in the s-plane may systematically differ between normal and pathological middle ears. This study establishes a methodology for examining the physical and mathematical properties of CAR using a concise parametric model. Pole-zero modeling accurately parameterizes CAR data, providing a foundation for detection and identification of middle ear pathologies.
This article is part of a Special Issue entitled “MEMRO 2012”.
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Using wideband reflectance to measure the impedance of the middle ear. by Withnell, R. H., Parent, P., Jeng, P. S., Allen, J. B. (2009). Hearing Journal, 62(10), 36, 38, 40-41.
An in situ calibration for hearing thresholds. by Withnell, R. H., Jeng, P. S., Allen, J. B. (2009). J. Acoust. Am., 125 (3), 1605-11.
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Quantifying how the sound delivered to the ear canal relates to hearing threshold has historically relied on acoustic calibration in physical assemblies with an input impedance intended to match the human ear (e.g., a Zwislocki coupler). The variation in the input impedance of the human ear makes such a method of calibration questionable. It is preferable to calibrate the acoustic signal in each ear individually. By using a calibrated sound source and microphone, the acoustic input impedance of the ear can be determined, and the sound delivered to the ear calibrated in terms of either (i) the incident sound pressure wave or (ii) that portion of the incident sound pressure wave transmitted to the middle ear and cochlea. Hearing thresholds expressed in terms of these quantities are reported, these in situ calibrations not being confounded by ear canal standing waves. Either would serve as a suitable replacement for the current practice of hearing thresholds expressed in terms of sound pressure level calibrated in a 6cc or 2cc coupler.
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Wideband Power Reflectance and Power Transmittance as Tools for Assessing Middle-Ear Function. by Jeng, P. S., Allen, J. B., Lapsley Miller, J. A., & Levitt, H. (2008). Perspectives on Hearing and Hearing Disorders in Childhood, 18(2), 44-57.
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Hearing screening programs using otoacoustic emissions can have high false positive rates, due to temporary middle-ear and outer-ear disorders. This is especially the case for newborns, infants, and young children. Standard tympanometry is limited, uncomfortable, and unreliable in young ears. By incorporating wideband acoustic power flow measurements into hearing screening (using the same equipment), middle-ear and outer-ear disorders can be detected, thus allowing for rescreening rather than more expensive audiological referrals. Wideband acoustic power flow is described in detail and four case examples are provided for adults and children.
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Wideband reflectance associated with otitis media in infants and children with cleft palate. by Hunter, L. L., Bagger-Sjoback, D., & Lundberg, M. (2008). Int J Audiol, 47 Suppl 1, S57-61.
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Wideband reflectance (WBR) is a method of middle-ear analysis that may provide more information and provide a more detailed look at the middle-ear system than tympanometry. WBR has the potential to improve efficiency of newborn hearing screening programs by reducing time needed to accurately diagnose middle-ear status. This prospective study compares wideband reflectance results with 226-Hz and 1000-Hz tympanometry and distortion product otoacoustic emissions in a group of infants and children with cleft lip and palate, who have not been treated with myringotomy or tubes. Results are also compared to normative data in children of similar ages using the same instrument and methods. Results demonstrate that wideband reflectance showed the highest level of agreement (88%) with DPOAE results.
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Wideband middle ear power measurement in infants and children. by Hunter, L. L., Tubaugh, L., Jackson, A., and Propes, S. (2008). J Am Acad Audiol, 19(4), 309-324.
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Wideband middle ear power (WMEP) measurement is a method of middle ear analysis that may provide improved diagnostic capability over single-frequency tympanometry. However, normative data, information about test-retest reliability, and results in clinical disorders are needed for clinical application. Normative and reliability data on WMEP in children three days to 47 months of age were obtained using a prototype commercial instrument. A prospective study was conducted in children enrolled from a well-child pediatric clinic (n = 97), with comparisons of age, gender, and middle ear status and stimulus type (broadband chirp and sine wave). No significant age effect for power reflectance across the age range of this study was found, except at 6000 Hz. Significantly higher-power reflectance was found for ears with poor ear status, specifically otitis media with effusion. Smaller but nonsignificant differences in power reflectance were found for ears with positive and negative tympanometric peak pressure. Intraclass correlation coefficients showed significant correlations of 0.68 to 0.97 at various test frequencies using the chirp stimulus. Multivariate analysis of variance showed no significant effect of stimulus type (sine wave vs broadband chirp), ear, or gender. These results provide normative data for wideband middle ear power analysis for infants and children from birth to age four years.
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Transient-evoked otoacoustic emissions: Preliminary results for validity of TEOAEs implemented on Mimosa Acoustics T2K measurement system v3.1.3. by Lapsley Miller, J. A., Boege, P., Marshall, L., & Jeng, P. S. (2004). (Technical Report No. 1232). Groton, CT.: Naval Submarine Medical Research Laboratory.
Stimulus-frequency otoacoustic emissions: Validity and reliability of SFOAEs implemented on Mimosa Acoustics SFOAE measurement system v2.1.18. by Lapsley Miller, J. A., Boege, P., Marshall, L., Shera, C., & Jeng, P. S. (2004). (Technical Report No. 1231). Groton, CT.: Naval Submarine Medical Research Laboratory.
