A comparison of ear-canal-reflectance measurement methods in an ear simulator.

Ear-canal reflectance has been researched extensively for diagnosing conductive hearing disorders and compensating for the ear-canal acoustics in non-invasive measurements of the auditory system. Little emphasis, however, has been placed on assessing measurement accuracy and variability. In this paper, a number of ear-canal-reflectance measurement methods reported in the literature are utilized and compared. Measurement variation seems to arise chiefly from three factors: the residual ear-canal length, the ear-probe insertion angle, and the measurement frequency bandwidth. Calculation of the ear-canal reflectance from the measured ear-canal impedance requires estimating the ear-canal characteristic impedance in situ. The variability in ear-canal estimated characteristic impedance and reflectance due to these principal factors is assessed in an idealized controlled setup using a uniform occluded-ear simulator. In addition, the influence of this measurement variability on reflectance-based methods for calibrating stimulus levels is evaluated and, by operating the condenser microphone of the occluded-ear simulator as an electro-static speaker, the variability in estimating the emitted pressure from the ear is determined. The various measurement methods differ widely in their robustness to variations in the three principal factors influencing the accuracy and variability of ear-canal reflectance.

On the calculation of reflectance in non-uniform ear canals.

Ear-canal reflectance is useful for quantifying the conductive status of the middle ear because it can be measured non-invasively at a distance from the tympanic membrane. Deriving the ear-canal reflectance requires decomposing the total acoustic pressure into its forward- and reverse-propagating components. This decomposition is conveniently achieved using formulas that involve the input and characteristic impedances of the ear canal. The characteristic impedance is defined as the ratio of sound pressure to volume flow of a propagating wave and, for uniform waveguides, the plane-wave characteristic impedance is a real-valued constant. However, in non-uniform waveguides, the characteristic impedances are complex-valued quantities, depend on the direction of propagation, and more accurately characterize a propagating wave in a non-uniform ear canal. In this paper, relevant properties of the plane-wave and spherical-wave characteristic impedances are reviewed. In addition, the utility of the plane-wave and spherical-wave reflectances in representing the reflection occurring due to the middle ear, calibrating stimulus levels, and characterizing the emitted pressure in simulated non-uniform ear canals is investigated and compared.

Diagnosing Middle Ear Pathology in 6- to 9-Month-Old Infants Using Wideband Absorbance: A Risk Prediction Model.

Purpose: The aim of this study was to develop a risk prediction model for detecting middle ear pathology in 6- to 9-month-old infants using wideband absorbance measures. Method: Two hundred forty-nine infants aged 23-39 weeks (Mdn = 28 weeks) participated in the study. Distortion product otoacoustic emissions and high-frequency tympanometry were tested in both ears of each infant to assess middle ear function. Wideband absorbance was measured at ambient pressure in each participant from 226 to 8000 Hz. Absorbance results from 1 ear of each infant were used to predict middle ear dysfunction, using logistic regression. To develop a model likely to generalize to new infants, the number of variables was reduced using principal component analysis, and a penalty was applied when fitting the model. The model was validated using the opposite ears and with bootstrap resampling. Model performance was evaluated through measures of discrimination and calibration. Discrimination was assessed with the area under the receiver operating characteristic curve (AUC); and calibration, with calibration curves, which plotted actual against predicted probabilities. Results: AUC of the fitted model was 0.887. The model validated adequately when applied to the opposite ears (AUC = 0.852) and with bootstrap resampling (AUC = 0.874). Calibration was satisfactory, with high agreement between predictions and observed results. Conclusions: The risk prediction model had accurate discrimination and satisfactory calibration. Validation results indicate that it may generalize well to new infants. The model could potentially be used in diagnostic and screening settings. In the context of screening, probabilities provide an intuitive and flexible mechanism for setting the referral threshold that is sensitive to the costs associated with true and false-positive outcomes. In a diagnostic setting, predictions could be used to supplement visual inspection of absorbance for individualized diagnoses. Further research assessing the performance and impact of the model in these contexts is warranted.

Quantifying undesired parallel components in Thévenin-equivalent acoustic source parameters.

The calibration of an ear probe to determine its Thévenin-equivalent acoustic source parameters facilitates the measurement of ear-canal impedance and reflectance. Existing calibration error metrics, used to evaluate the quality of a calibration, are unable to reveal undesired parallel components in the source parameters. Such parallel components can result from, e.g., a leak in the ear tip or improperly accounting for evanescent modes, and introduce errors into subsequent measurements of impedance and reflectance. This paper proposes a set of additional error metrics that are capable of detecting such parallel components by examining the causality of the source admittance in the frequency domain and estimating the source pressure in the time domain. The proposed and existing error metrics are applied to four different calibrations using two existing calibration methods, representing typical use cases and introducing deliberate parallel components. The results demonstrate the capability of the proposed error metrics in identifying various undesired components in the source parameters that might otherwise go undetected.

[The characteristics of broad-band tympanometry in the volunteers with the unaffected hearing]. / Pokazateli shirokopolosnoi timpanometrii u lits s normal'nym slukhom.

AIM: The objective of the present work was to elucidate the characteristics of broad-band tympanometry in the healthy subjects with the unaffected hearing ability. The study involved 54 volunteers (27 men and 27 women) at the age from 21 to 55 years exhibiting no pathologic changes in the ear system as confirmed by the tone threshold audiometry, otoacoustic emission, tympaometry at a frequency of 226 Hz, and reflexometry. All the participants of the study underwent absorbance measurements by broad-band tympanometry within the frequency range from 226 to 8,000 Hz at an ambient pressure. Five parameters have been detected which reflected the major characteristics of the absorbance curve, such as the maximum sound power absorbance ratio; the frequency at which the ear structures absorbed the maximum sound power; the frequency at which the absorbance ratio bounces off the plateau; the frequency at which the absorbance ratio plummets to plateau; and the frequency range within which the absorbance ratio underwent the most pronounced changes. The results obtained in the present study give evidence of response stability and the absence of the statistically significant differences in the absorbance parameters between the men and women obtained by their analysis for the ipsilateral and contralateral ears.

Wideband Tympanometry Normative Data for Different Age Groups in Turkish Population.

OBJECTIVE: Studies on the use of wideband tympanometry (WBT) for the evaluation of middle ear pathologies have been increasing gradually in recent years. However, studies regarding normative data of WBT are not sufficient. The aim of this study was to determine normative values of WBT for different age groups in Turkish population. MATERIALS AND METHODS: One hundred fifty volunteers from five age-related groups were included in this study. Values of resonance frequency (RF), absorbance percentage according to frequency, maximum absorbance ratio, and maximum absorbance frequency were obtained using WBT. Measurements were recorded at a pressure of 0 decapascal (daPa) using a sound stimulus given at 90±3 decibel sound pressure level (dB SPL). RESULTS: The RF was detected to be significantly lower only in the group of subjects in the age range of 0-1 month. The absorbance value at 250 Hz was detected to be significantly higher in the age groups of 0-1 month and 1 month-2 years than in the other groups. CONCLUSION: We believe that the findings obtained in this study would be helpful in determining normative data regarding WBT; by the determination of this normative data, the clinical use of WBT would become widespread.

Wideband Tympanometry Normative Data for Turkish Young Adult Population.

OBJECTIVE: The aim of this study was to obtain norm values for a young adult Turkish group and to investigate the differences between female and male subjects in terms of wideband tympanometry. MATERIALS AND METHODS: One hundred ten young adult volunteers (mean±SD: 21.1±1.9 years) participated in this study. The measurements of wideband tympanometry were performed at octave frequencies between 226 Hz and 8000 Hz using Titan version 3.1. The stimulus level was set at 100 dB peSPL. RESULTS: A cross-sectional study design was used. In total, 218 ears were tested. A significant relationship was found between gender and absorbance values for the frequency band from 3100 Hz to 6900 Hz. The difference between the middle ear resonance frequency and ear canal volume (ECV) of the male and female subjects was also found to be significant. The difference in ECV may result from the difference in body size between the male and female subjects because there was a significant relationship among ECV and the height and weight. CONCLUSION: According to these results, it can be concluded that using separate norms for males and females may increase test specificity and sensitivity for the diagnosis of disorders, such as ossicular discontinuity and tympanic membrane perforations, affecting the high-frequency region.

Repeatability of transient-evoked otoacoustic emissions in young adults.

BACKGROUND: The aim of this study was to evaluate the repeatability and variability of TEOAE characteristics in hearing screening tests performed under practical conditions on normal subjects. MATERIAL/METHODS: A group of 11 young, normal-hearing subjects aged 19-24 years was tested. They were examined otologically and audiologically prior to the tests and no ear pathologies were found. Responses were acquired with a commercially available instrument (Integrity, Vivosonic Inc.) using a standardized OAE protocol. The TEOAE tests were repeated 3 times in each subject at random intervals within 24 h. The analyzed parameters of interest were: (i) whole wave reproducibility (WWR) and; (ii) signal-to-noise ratio (SNR). RESULTS: WWR and SNR did not differ significantly among the 3 measurement sessions. In most cases the differences in WWR among measurements were around 1-2% and for SNRs they were 1-4 dB SNRs and were highest in the 1-2 kHz range. TEOAE-based tests can be useful tools for hearing screening. CONCLUSIONS: The tests can give reliable results provided that adequate procedures are used and low-noise conditions are ensured. The tests are best complemented with other examinations to widen the range of ear pathologies able to be detected.

Hearing threshold levels for a population of 11 to 35 year old Australian females and males.

OBJECTIVE: Detailed information on the hearing threshold levels (HTLs) of young Australians was gathered as part of a large-scale study of the relationship between HTL and leisure-noise exposure in young Australians. DESIGN: HTL data for the study population (18-35 year olds) was carefully collected, as well as otoscopy, tympanometry, contra-lateral acoustic reflexes, and otoacoustic emissions (transient and distortion product), together with a comprehensive hearing health history - both past and present. STUDY SAMPLE: The sample cohort consisted of 1407 individuals, females and males. RESULTS: Prior to analysis, HTL data were filtered according to both a 'Low' and 'High' set of exclusion criteria. The results obtained for both high-screen and low-screen datasets were around +5 dB above the traditionally accepted values of audiometric zero. This is consistent with previous published reports. CONCLUSION: Comparison with 'ISO 7029 Acoustics: Statistical distribution of hearing thresholds as a function of age' indicated that threshold values for this dataset have a similar distribution to those of the Standard. This data provides a suitable reference HTL ('normative') database for young Australians.

Does temperature effect tympanometric evaluation of ear canal volume? A scientific study using an Ear Canal Model.

Tympanometric evaluation is a routine part of the complete otological examination. Although tympanometry when performed in standard conditions is known to accurately and precisely assess ear canal volume, the effects of variation in temperature have not been reported upon. This study examines the effect of temperature on the capability of the tympanometer to accurately evaluate external auditory canal volume in both simple and partially obstructed Ear Canal Models. An Ear Canal Model was designed using simple laboratory equipment including a 5 ml calibrated clinical syringe. This was attached to the sensing probe of a Kamplex tympanometer. Two basic trials were undertaken: (a) evaluation of the effect of temperature on the tympanometer in simple canal volume measurement and (b) assessing canal volume with partial canal occlusion. These studies were conducted at 0, 10, 20 and 30 °C in a Thermotron climatic chamber. 1,400 individual test scenarios were completed over the two arms of the study. At volumes of 1.4 cm(3) or below, tympanometry had a very high level of correlation (Spearman's ρ = 1) with the actual volume present at all tested temperatures except 0 °C. There was no significant relationship between temperature and degree of error in ear canal volume measurement in both simple and partially occluded models. The ability of the Kamplex tympanometer to accurately and precisely assess ear canal volume in this scientific model in both simple and partially occluded scenarios up to a volume of 1.4 cm(3) is not effected by ambient temperature. These findings suggest the Kamplex tympanometer could be used as an effective objective tool in both laboratory and human models of the external auditory canal.

[The intraoperative monitoring of the gas pressure in the middle ear].

The objective of the present work was to elucidate the patterns and mechanisms underlying the changes of gas pressure in the middle ear during the operation of stapedoplasty with a view to the application of the data obtained for objective recording of the stapedial reflex at the time of surgical intervention. Ten subjects with the unaffected hearing function were recruited for the study. Tympanometry was carried out at one-minute intervals starting from the onset of feeding nitrogen monooxide till the completion of septoplasty. It was shown that the surgical intervention under inhalation anesthesia is associated with periodic rises and drops in the gas pressure in the middle ear within a range from 500 dPA to 88 dPA with a period from 5.7 to 22 minutes. It is argued that these changes can be attributed to the periodic opening of the Eustachian tube when the gas pressure reaches a certain level due to continuous diffusion of nitrogen monooxide into the middle ear (the "preventive" release of pressure) followed by the passive closure of the auditory tube. The authors propose based on the results of the study recommendations on the performance of stapedial reflexometry during the surgical intervention with the use of impedancometry.

[Normative values of middle ear resonance frequency in normal hearing adults]. / Normal isiten yetiskinlerde orta kulak rezonans frekansi normatif degerleri.

OBJECTIVES: This study aims to determine the normative values of middle ear resonance frequency in healthy adults. PATIENTS AND METHODS: Sixty adult volunteers (32 females, 28 males; mean age 31.8±7.1 years; range 21 to 46 years) with normal otoscopic examination, audiometry and electroacoustic immitancemetry findings were enrolled in the study. The middle ear resonance frequencies were calculated by multifrequency tympanometry. RESULTS: The mean resonance frequency for all volunteers was 999.6±134.9 Hz. The mean resonance frequency was 1020.8±140.6 Hz for the right ear, and 978.3±180.5 Hz for the left ear. The mean resonance frequencies for the right- and left-side were 1023.2±146.9 Hz and 912.5±177.8 Hz in males, and 1018.8±137.2 Hz and 1035.9±164.7 Hz in females, respectively. There was no statistically significant difference in the mean resonance frequency of the right ears between the males and females (p=0.9), whereas the mean resonance frequency of the left ears was statistically significantly higher in females (p=0.007). CONCLUSION: The middle ear resonance frequency values may vary according to the side of the ear or gender.

Wideband acoustic immittance normative data: ethnicity, gender, aging, and instrumentation.

This article describes the effect of ethnicity, gender, aging, and instrumentation on wideband acoustic immittance (WAI). This is an important topic to investigate as the goal of any audiological test is optimize the test's sensitivity and specificity. One way to improve the test's sensitivity and specificity is to reduce the variability of the normative data. The impact of the aforementioned demographic characteristics on WAI norms has been reviewed, and where applicable its potential impact on clinical outcome has been discussed. Overall, differences observed between Caucasian and Chinese ethnic groups in adults population may warrant the use of ethnicity-specific norms especially for detection of otosclerosis; however, these differences in the school-aged children are not large enough to warrant the use of ethnicity-specific norms. It is important to explore whether the observed differences between Caucasian and Chinese ethnic groups is due to body-size indices and whether these differences can be replicated in other East Asian ethnic groups that share similar body-size indices. The differences observed between school-aged children and adults could also potentially impact clinical decision analysis. Therefore, use of age-specific norm is recommended. The differences in WAI between different systems are not clinically significant, and the use of instrument-specific norms does not result in improved test performance at least for the detection of otosclerosis. However, measuring WAI at ambient pressure (static) or at pressure corresponding to the peak (dynamic mode) could potentially impact the normative data and may prove to be clinically useful in cases of negative and positive middle ear pressure.

Wideband acoustic immittance: tympanometric measures.

Wideband tympanometry (WT) measurements provide a view of the acoustic response properties of the middle ear over a broad range of frequencies and ear-canal pressures. These measurements show sensitivity to trends in ear-canal/middle ear maturation and changes in middle ear status as a result of different types of dysfunction. While results from early WT work showed improvements over ambient wideband tests in terms of test performance for identifying middle ear dysfunction and conductive hearing loss (CHL), more recent studies have shown high, but similar test performance for both ambient and tympanometric wideband tests. Case study and group results presented in this article, demonstrating the sensitivity of WT to middle ear dysfunction, CHL, and maturational changes in the middle ear, are promising and suggest the need for additional investigations in individual subjects and large subject populations. Future research should focus on identifying key predictors of developmental trends, middle ear dysfunction, and CHL in an effort to develop middle ear tests with high sensitivity and specificity. Technological advances, more accessibility to equipment, and evolving data analysis techniques should encourage progress in the areas of WT research and clinical application.

Factors that introduce intrasubject variability into ear-canal absorbance measurements.

Wideband immittance measures can be useful in analyzing acoustic sound flow through the ear and also have diagnostic potential for the identification of conductive hearing loss as well as causes of conductive hearing loss. To interpret individual measurements, the variability in test­retest data must be described and quantified. Contributors to variability in ear-canal absorbance­based measurements are described in this article. These include assumptions related to methodologies and issues related to the probe fit within the ear and potential acoustic leaks. Evidence suggests that variations in ear-canal cross-sectional area or measurement location are small relative to variability within a population. Data are shown to suggest that the determination of the Thévenin equivalent of the ER-10C probe introduces minimal variability and is independent of the foam ear tip itself. It is suggested that acoustic leaks in the coupling of the ear tip to the ear canal lead to substantial variations and that this issue needs further work in terms of potential criteria to identify an acoustic leak. In addition, test­retest data from the literature are reviewed.

Consensus statement: Eriksholm workshop on wideband absorbance measures of the middle ear.

The participants in the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear developed statements for this consensus article on the final morning of the Workshop. The presentations of the first 2 days of the Workshop motivated the discussion on that day. The article is divided into three general areas: terminology; research needs; and clinical application. The varied terminology in the area was seen as potentially confusing, and there was consensus on adopting an organizational structure that grouped the family of measures into the term wideband acoustic immittance (WAI), and dropped the term transmittance in favor of absorbance. There is clearly still a need to conduct research on WAI measurements. Several areas of research were emphasized, including the establishment of a greater WAI normative database, especially developmental norms, and more data on a variety of disorders; increased research on the temporal aspects of WAI; and methods to ensure the validity of test data. The area of clinical application will require training of clinicians in WAI technology. The clinical implementation of WAI would be facilitated by developing feature detectors for various pathologies that, for example, might combine data across ear-canal pressures or probe frequencies.

Audition assessment using the NIH Toolbox.

The NIH Toolbox project has assembled measurement tools to assess a wide range of human perception and ability across the lifespan. As part of this initiative, a small but comprehensive battery of auditory tests has been assembled. The main tool of this battery, pure-tone thresholds, measures the ability of people to hear at specific frequencies. Pure-tone thresholds have long been considered the "gold standard" of auditory testing, and are normally obtained in a clinical setting by highly trained audiologists. For the purposes of the Toolbox project, an automated procedure (NIH Toolbox Threshold Hearing Test) was developed that allows nonspecialists to administer the test reliably. Three supplemental auditory tests are also included in the Toolbox auditory test battery: assessment of middle-ear function (tympanometry), speech perception in noise (the NIH Toolbox Words-in-Noise Test), and self-assessment of hearing impairment (the NIH Toolbox Hearing Handicap Inventory Ages 18-64 and the NIH Toolbox Hearing Handicap Inventory Ages 64+). Tympanometry can help differentiate conductive from sensorineural pathology. The NIH Toolbox Words-in-Noise Test measures a listener's ability to perceive words in noisy situations. This ability is not necessarily predicted by a person's pure-tone thresholds; some people with normal hearing have difficulty extracting meaning from speech sounds heard in a noisy context. The NIH Toolbox Hearing Handicap Inventory focuses on how a person's perceived hearing status affects daily life. The test was constructed to include emotional and social/situational subscales, with specific questions about how hearing impairment may affect one's emotional state or limit participation in specific activities. The 4 auditory tests included in the Toolbox auditory test battery cover a range of auditory abilities and provide a snapshot of a participant's auditory capacity.

Interaural multiple frequency tympanometry measures: clinical utility for unilateral conductive hearing loss.

BACKGROUND: Tympanometry is a routine clinical measurement of the acoustic immittance of the ear as a function of ear canal air pressure. The 226 Hz tympanogram can provide clinical evidence for conditions such as a tympanic membrane perforation, Eustachian tube dysfunction, middle ear fluid, and ossicular discontinuity. Multiple frequency tympanometry using a range of probe tone frequencies from low to high has been shown to be more sensitive than a single probe tone tympanogram in distinguishing between mass- and stiffness-related middle ear pathologies (Colletti, 1975; Funasaka et al, 1984; Van Camp et al, 1986). PURPOSE: In this study we obtained normative measures of middle ear resonance by using multiple probe tone frequency tympanometry. Ninety percent ranges for middle ear resonance and for interaural differences were calculated. RESEARCH DESIGN: In a mixed design, normative data were collected from both ears of male and female adults. STUDY SAMPLE: Twelve male and 12 female adults with normal hearing and normal middle ear function participated in the study. DATA COLLECTION AND ANALYSIS: Multiple frequency tympanograms were recorded with a commercially available immittance instrument (GSI Tympstar) to obtain estimates of middle ear resonant frequency (RF) using ΔB, positive tail, and negative tail methods. Data were analyzed using three-way mixed analyses of variance with gender as a between-subject variable and ear and method as within-subject variables. T-tests were performed, using the Bonferroni adjustment, to determine significant differences between means. RESULTS: Using the positive and negative tail methods, a wide range of approximately 500 Hz was found for middle ear resonance in adults with normal hearing and normal middle ear function. The difference in RF between an individual's ears is small with 90% ranges of approximately ±200 Hz, indicating that the right ear RF should be either 200 Hz higher or lower in frequency compared to the left ear. This was true for both negative and positive tail methods. CONCLUSION: Ninety percent ranges were calculated to determine the difference in middle ear resonance expected between an individual's ears. These ranges can provide critical normative values for determining how pathology in an ear with a unilateral conductive hearing loss is altering the mass or stiffness characteristics of the middle ear system.

Using different criteria to diagnose (central) auditory processing disorder: how big a difference does it make?

PURPOSE: To quantify how 9 different diagnostic criteria affected potential (central) auditory processing disorder ([C]APD) diagnoses in a large sample of children referred for (central) auditory processing ([C]AP) assessment. METHOD: A file review was conducted on 150 children (94 boys and 56 girls; ages 7.0-15.6 years) with normal peripheral hearing who had completed a (C)AP assessment involving low-pass filtered speech, competing sentences, 2-pair dichotic digits, and frequency patterns with linguistic and nonlinguistic report. Each child was classified as having or not having (C)APD based on 9 different sets of diagnostic criteria drawn from published technical reports, position statements, and selected research. RESULTS: The rates of potential (C)APD diagnosis ranged from 7.3% for the strictest criteria to 96.0% for the most lenient criteria. CONCLUSIONS: Until greater consensus is reached, any diagnosis of (C)APD should be qualified by an explicit statement of the criteria used. Calls to abandon the use of (C)APD as a global label should also be supported.