An Absorbance Peak Template for Clinical Assessment of Sound Conduction in Newborn Ears.

PURPOSE: Power absorbance measures recorded over a wide range of frequencies allow for clinical inferences about the outer/middle ears' acoustic mechanics. A frequency-dependent feature in the newborn wideband absorbance response, the prominent mid-frequency absorbance peak, has been linked to middle-ear resonance. However, current normative methods were not designed to assess subtle changes in such features. This work aims to develop and validate an absorbance peak template (APT) for assessment of absorbance peaks in newborns. Additional objectives are to compare test performance of absorbance peaks and APTs to existing normative methods, to demonstrate APT-based methods for categorization of abnormal absorbance peaks, and to describe absorbance peak test-retest variability. METHOD: Peak absorbance and peak frequency were analyzed in a training data set (490 measurements in 84 newborn ears who passed transient evoked otoacoustic emissions [TEOAEs] screenings), and an APT was developed by computing normal limits on these two absorbance peak variables. Split-set analysis evaluated the reproducibility of APT, and test-retest analysis was performed. Test performance analysis, conveyed by area under the receiver operating characteristic curve (AROC) and 95% confidence intervals (CIs), compared absorbance peak variables to absorbance area indices (AAIs) in a validation data set (359 ears that passed distortion-product OAE [DPOAE] screening and 64 ears that failed). APT-based assessment paradigms for normal and abnormal ears were compared to the common absorbance normative range paradigm. RESULTS: Split-set analysis demonstrated a good reproducibility of APT, and test-retest of absorbance peak variables showed that they were stable measures for clinical assessment. Test performance of peak absorbance (AROC = 0.83; 95% CI [0.77, 0.88]) was comparable to the top-performing AAI variables (AROC = 0.85; 95% CI [0.80, 0.90]). APT-based assessment categorized measurements based on their peak absorbance and peak frequency and enhanced the detection of subtle frequency changes that were missed by the normative range method. CONCLUSION: Analysis of absorbance peaks guided by APT has the potential to simplify and improve assessments of sound conduction pathways in newborn ears and can be used together with or in-place of current methods for analysis of wideband absorbance data.

Erratum: The Rise and Fall of Aural Acoustic Immittance Assessment Tools.

[This corrects the article DOI: 10.1055/s-0043-1764139.].

Implementation of Wideband Acoustic Immittance in Clinical Practice: Relationships among Audiologic and Otologic Findings.

A number of studies have produced normative and developmental data and examples of wideband acoustic immittance (WAI) obtained in ears with pathologies and or dysfunction. However, incorporation of this tool into clinical audiology and otolaryngology practice has been slower than expected, potentially due to challenges with interpretation, integration into existing test batteries, and confidence in practical application. This article presents information aimed at helping clinicians increase their confidence in using this new tool by becoming more familiar and making connections with the ways that WAI outcomes both align with and add to standard immittance, audiometric and otologic diagnostic test outcomes. This article presents several case studies to demonstrate the use of WAI in realistic clinical settings. Each case presents a brief background, case history, audiologic/otologic findings, and initial recommendations, followed by a discussion on how the inclusion of WAI test outcomes aids in diagnostic decisions. The overall aim of this work is to identify the relationships among different diagnostic test outcomes, to demonstrate basic WAI interpretation principles, and encourage the reader to engage with this diagnostic tool in clinical practice.

The Rise and Fall of Aural Acoustic Immittance Assessment Tools.

Clinical assessment of middle ear function has undergone multiple transformations and developments since the first acoustic impedance measurements were made in human ears nearly a century ago. The decades following the development of the first acoustic impedance bridge by Metz in 1946 witnessed a series of technological advancements leading to the widespread use of single-frequency admittance tympanometry in the 1960s. In the 1970s, multi-frequency and multi-component tympanometry (MFT) emerged for clinical use, allowing for a better understanding of the middle ear acoustic-mechanical response at frequencies between 200 and 2,000 Hz. MFT has not gained widespread clinical adoption despite its advantages over single-frequency tympanometry. More recent technological developments enabled assessment for frequencies greater than 2,000 Hz, leading to the advent of wideband acoustic immittance measures with capabilities for comprehensive assessment of middle ear acoustic mechanics, and a great potential for use of acoustic immittance testing in various diagnostic practices. This article reviews important historical markers in the development and operation of middle ear assessment tools and analysis methods. Technical and clinical factors underlying the emergence and adoption of different acoustic immittance tests as a standard of clinical practice are described. In addition, we discuss the likelihood for widespread adoption of wideband acoustic immittance and wideband tympanometry in future clinical practice.

Pressurized transient otoacoustic emissions measured using click and chirp stimuli.

Transient-evoked otoacoustic emission (TEOAE) responses were measured in normal-hearing adult ears over frequencies from 0.7 to 8 kHz, and analyzed with reflectance/admittance data to measure absorbed sound power and the tympanometric peak pressure (TPP). The mean TPP was close to ambient. TEOAEs were measured in the ear canal at ambient pressure, TPP, and fixed air pressures from 150 to -200 daPa. Both click and chirp stimuli were used to elicit TEOAEs, in which the incident sound pressure level was constant across frequency. TEOAE levels were similar at ambient and TPP, and for frequencies from 0.7 to 2.8 kHz decreased with increasing positive and negative pressures. At 4-8 kHz, TEOAE levels were larger at positive pressures. This asymmetry is possibly related to changes in mechanical transmission through the ossicular chain. The mean TEOAE group delay did not change with pressure, although small changes were observed in the mean instantaneous frequency and group spread. Chirp TEOAEs measured in an adult ear with Eustachian tube dysfunction and TPP of -165 daPa were more robust at TPP than at ambient. Overall, results demonstrate the feasibility and clinical potential of measuring TEOAEs at fixed pressures in the ear canal, which provide additional information relative to TEOAEs measured at ambient pressure.

Characteristics of wideband acoustic immittance in patients with middle-ear dysfunction.

BACKGROUND: Wideband acoustic immittance (WAI) measurements are a relatively new class of aural acoustic tests that have shown promise as useful tools for evaluating middle-ear status. A growing body of work has described WAI for infants, children, and adults with normal middle-ear function, but a relatively limited number of studies have investigated the influence of specific middle-ear disorders on WAI. Although emerging WAI research data show promising results, additional measurements from ears of patients with a variety of middle-ear disorders are needed. PURPOSE: The aims of the present study were to (1) obtain WAI data from patients with a variety of middle-ear conditions, (2) examine relationships between WAI data relative to standard audiometric tests, and (3) identify patterns or profiles in WAI data within and among patients with different middle-ear conditions. RESEARCH DESIGN: A descriptive study. STUDY SAMPLE: Participants included 30 children and two adults with a variety of middle-ear disorders who were recruited from clinical audiology settings. DATA COLLECTION/ANALYSIS: Experimental ambient and tympanometric WAI data were gathered along with standard audiometric test data as part of clinical audiology appointments. Single-subject and small-group data sets for ears of patients with suspected otitis media with effusion (sOME), pressure equalization (PE) tubes, negative tympanometric peak pressure (TPP), tympanoplasty, and cerumen impaction were obtained. Qualitative analysis and descriptive statistics (means and percentiles) were used to characterize the data. RESULTS: Group mean absorbance for ears in the sOME group was reduced across the majority of frequencies; absorbance for ears with negative TPP was also reduced, although to a lesser degree. Absorbance patterns for ears with PE tubes show even greater differences because of the effects of the tube and open middle-ear cavity. WAI from ears with a tympanoplasty and cerumen impaction was suggestive of middle-ear dysfunction in the presence of normal single-frequency tympanometry. Percentile (5th, 50th, and 95th) plots for absorbance and other WAI quantities of admittance level, admittance phase, and equivalent ear-canal volume calculated for the sOME, negative TPP, and PE tube groups showed distinctive profiles that might be useful for discrimination of different middle-ear pathologies. Quantities from wideband tympanometry, including 250- and 1000-Hz single-frequency admittance tympanometric data were also derived. CONCLUSIONS: WAI measurements for some middle-ear conditions were consistent with patterns and profiles previously reported in the literature. WAI profiles for other middle-ear conditions, which had not been previously reported in the literature, were presented. Relationships between WAI data and results of standard audiometric tests were generally consistent with expectations. However, in some cases, WAI measurements were suggestive of middle-ear dysfunction despite normal 226-Hz admittance tympanometric findings.

Effects of ear-canal static pressure on pure-tone thresholds and wideband acoustic immittance.

BACKGROUND: Wideband acoustic immittance (WAI) measures provide information about middle-ear function across the traditional audiometric frequency range from 0.25 to 8.0 kHz. Recent studies have found that WAI is effective in predicting the presence of conductive hearing loss (CHL). It is not known whether WAI can accurately estimate the degree of threshold shift caused by CHL. PURPOSE: The purpose of the present study was to evaluate the relationship between changes in pure-tone threshold and changes in wideband absorbance and acoustic conductance levels induced by positive and negative ear-canal static pressure. STUDY SAMPLE: Twenty young adult subjects with normal hearing and a negative history of middle-ear disorders participated in the study. DATA COLLECTION AND ANALYSIS: Experimental pure-tone thresholds at 0.5 and 2.0 kHz were estimated by using a three-interval, three-alternative forced-choice adaptive psychometric procedure under three conditions: ambient ear-canal pressure, +200 daPa static pressure, and -200 daPa static pressure. Wideband absorbance and conductance were obtained in the same subjects by using a Welch Allyn prototype diagnostic middle ear analyzer. Changes in pure-tone threshold from the ambient pressure condition to the static pressure condition were evaluated by using a paired-samples t test and Pearson product-moment correlation. RESULTS: Wideband middle-ear absorbance and conductance at ambient pressure in this study were consistent with published data in adults with normal hearing. The mean change in threshold at 0.5 and 2.0 kHz with +200 daPa or -200 daPa ear-canal static pressure was similar to the mean change in absorbance and conductance levels in the same conditions. However, there was one statistically significant difference between the shift in pure-tone threshold and the change in conductance level for the +200 daPa pressure condition for 2.0 kHz, with the change in threshold being 1.5 dB greater than the change in conductance level (t = 2.39, p = 0.03). In contrast to the good performance of WAI measures in predicting mean threshold shifts caused by ear-canal pressure, the shifts in WAI were not correlated with threshold shifts. Thus WAI was not well suited to predict individual threshold changes caused by ear-canal static pressure. CONCLUSIONS: For the conditions of this study, results suggest that mean change in absorbance or conductance level caused by ear-canal static pressure of +200 daPa or -200 daPa provides a good estimate of the change in pure-tone threshold in the same conditions. However, individual threshold change was not accurately predicted by the change in absorbance or conductance level.

Wideband acoustic immittance measures: developmental characteristics (0 to 12 months).

Rapid developmental changes of the peripheral auditory system in normal infants occur in the first year of life. Specifically, the postnatal development of the external and middle ear affects all measures of external and middle ear function including wideband acoustic immittance(WAI). This article provides an overview of WAI studies in newborns and infants from a developmental perspective. Normative WAI data in newborns are fairly consistent across studies. However, there are discrepancies in some WAI measures between studies, possibly due to differences in sampling, methodology, and instrumentation. Accuracy of WAI measurements is compromised when a good probe seal cannot be maintained during testing or an inaccurate estimate of the cross-sectional area of the ear canal of newborns occurs. Comparison of WAI data between age groups from 0 to 12 months reveals maturation effects. Additional age-specific longitudinal and cross-sectional normative WAI data for infants from birth to 12 months are required to validate and consolidate existing data.

Pediatric applications of wideband acoustic immittance measures.

Wideband acoustic immittance (WAI) measures have potential capability to improve newborn hearing screening outcomes and middle ear diagnosis for infants and children. To fully capitalize on these immittance measures for pediatric hearing care, developmental and pathologic effects need to be fully understood. Published literature on wideband immittance (reflectance, absorbance, tympanometry, and acoustic reflexes) is reviewed in this article to determine pathologic effects in newborns, infants, and children relative to standard audiologic tests such as otoacoustic emissions (OAEs), standard tympanometry, air and bone conduction auditory brainstem response, and otoscopy. Infants and children with surgically confirmed otitis media with effusion have lower absorbance in the mid-frequency range (1 to 3 kHz) for the affected ear(s). Newborns that do not pass OAE screening at birth also have lower absorbance for frequencies from 1 to 3 kHz, suggesting that nonpass results are frequently associated with middle ear issues at birth. In Newborn Hearing Screening Programs, WAI may help to interpret hearing screening results. Conclusions are limited by the fact that the true status of the middle ear and cochlea are not known for newborns and infants in studies that use OAE or tympanometry as the reference standard. Likelihood ratios for reflectance against surgery gold standards range from diagnostically suggestive to informative. Although some of the results are promising, limited evidence and methodological considerations restrict the conclusions that can be drawn regarding the diagnostic accuracy of WAI technologies in infants and children. Additional investigations using stronger gold standard comparisons are needed to determine which tools can most accurately predict middle ear status in the pediatric population.

Acoustic reflex measurement.

Middle ear muscle reflex (MEMR) measurements have been a part of the standard clinical immittance test battery for decades as a cross-check with the behavioral audiogram and as a way to separate cochlear from retrocochlear pathologies. MEMR responses are measured in the ear canal by using a probe stimulus (e.g., single frequency or broadband noise) to monitor admittance changes elicited by a reflex-activating stimulus. In the clinical MEMR procedures, one test yields changes in a single measurement (i.e., admittance) at a single pure tone (e.g., 226 or 1000 Hz). In contrast, for the wideband acoustic immittance (WAI) procedure,one test yields information about multiple measurements (e.g., admittance, power reflectance, absorbance) across a wide frequency range (e.g., 250 to 8000 Hz analysis bandwidth of the probe). One benefit of the WAI method is that the MEMR can be identified in a single test regardless of the frequency at which the maximum shift in the immittance measurement occurs; this is beneficial because maximal shifts in immittance vary as a function of age and other factors. Another benefit is that the wideband response analysis yields lower MEMR thresholds than with the clinical procedures. Lower MEMR thresholds would allow for MEMR decay tests in ears in which the activator levels could not be safely presented. Finally, the WAI procedures can be automated with objective identification of the MEMR, which would allow for use in newborn and other screening programs in which the tests are completed by nonaudiological personnel.

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.

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.

Wideband aural acoustic absorbance predicts conductive hearing loss in children.

OBJECTIVE: This study tested the hypothesis that wideband aural absorbance predicts conductive hearing loss (CHL) in children medically classified as having otitis media with effusion. DESIGN: Absorbance was measured in the ear canal over frequencies from 0.25 to 8 kHz at ambient pressure or as a swept tympanogram. CHL was defined using criterion air-bone gaps of 20, 25, and 30 dB at octaves from 0.25 to 4 kHz. A likelihood-ratio predictor of CHL was constructed across frequency for ambient absorbance, and across frequency and pressure for absorbance tympanometry. Performance was evaluated at individual frequencies and for any frequency at which a CHL was present. STUDY SAMPLE: Absorbance and conventional 0.226-kHz tympanograms were measured in children of age three to eight years with CHL and with normal hearing. RESULTS: Absorbance was smaller at frequencies above 0.7 kHz in the CHL group than the control group. Based on the area under the receiver operating characteristic curve, wideband absorbance in ambient and tympanometric tests were significantly better predictors of CHL than tympanometric width, the best 0.226-kHz predictor. Accuracies of ambient and tympanometric wideband absorbance did not differ. CONCLUSIONS: Absorbance accurately predicted CHL in children and was more accurate than conventional 0.226-kHz tympanometry.

Determining the presence or absence of middle ear disorders: an evidence-based systematic review on the diagnostic accuracy of selected assessment instruments.

PURPOSE: To conduct an evidence-based systematic review on the state of the evidence and the diagnostic accuracy of multifrequency tympanometry (MFT), 1000 Hz tympanometry, and wideband acoustic transfer functions in determining the presence or absence of middle ear disorders. METHOD: A systematic search of the literature published between 1975 and 2011 was conducted. Articles meeting the selection criteria were appraised by 2 reviewers and vetted by a 3rd for methodological quality. RESULTS: Ten studies were included and focused on participants with otosclerosis or otitis media. Two studies investigated 1000 Hz tympanometry, 7 examined MFT, and 2 addressed wideband reflectance (WBR). Methodological quality varied. Positive likelihood ratios (LR+) were predominantly uninformative for MFT and were mixed for 1000 Hz tympanometry. LR+ values for WBR ranged from diagnostically suggestive to informative. Negative likelihood ratios (LR-) for 1000 Hz tympanometry and WBR were at least diagnostically suggestive. LR- values for MFT were mixed, with half considered clinically uninformative and half considered diagnostically suggestive. CONCLUSIONS: Although some of the results are promising, limited evidence and methodological considerations restrict the conclusions that can be drawn regarding the diagnostic accuracy of these technologies. Additional investigations are needed to determine which tools can most accurately predict middle ear status.

Wideband acoustic transfer functions predict middle-ear effusion.

OBJECTIVES/HYPOTHESIS: Compare the accuracy of wideband acoustic transfer functions (WATFs) measured in the ear canal at ambient pressure to methods currently recommended by clinical guidelines for predicting middle-ear effusion (MEE). STUDY DESIGN: Cross-sectional validating diagnostic study among young children with and without MEE to investigate the ability of WATFs to predict MEE. METHODS: WATF measures were obtained in an MEE group of 44 children (53 ears; median age, 1.3 years) scheduled for middle-ear ventilation tube placement and a normal age-matched control group of 44 children (59 ears; median age, 1.2 years) with normal pneumatic otoscopic findings and no history of ear disease or middle-ear surgery. An otolaryngologist judged whether MEE was present or absent and rated tympanic-membrane (TM) mobility via pneumatic otoscopy. A likelihood-ratio classifier reduced WATF data (absorbance, admittance magnitude and phase) from 0.25 to 8 kHz to a single predictor of MEE status. Absorbance was compared to pneumatic otoscopy classifications of TM mobility. RESULTS: Absorbance was reduced in ears with MEE compared to ears from the control group. Absorbance and admittance magnitude were the best single WATF predictors of MEE, but a predictor combining absorbance, admittance magnitude, and phase was the most accurate. Absorbance varied systematically with TM mobility based on data from pneumatic otoscopy. CONCLUSIONS: Results showed that absorbance is sensitive to middle-ear stiffness and MEE, and WATF predictions of MEE in young children are as accurate as those reported for methods recommended by the clinical guidelines.

Wideband acoustic-reflex test in a test battery to predict middle-ear dysfunction.

A wideband (WB) aural acoustical test battery of middle-ear status, including acoustic-reflex thresholds (ARTs) and acoustic-transfer functions (ATFs, i.e., absorbance and admittance) was hypothesized to be more accurate than 1-kHz tympanometry in classifying ears that pass or refer on a newborn hearing screening (NHS) protocol based on otoacoustic emissions. Assessment of middle-ear status may improve NHS programs by identifying conductive dysfunction and cases in which auditory neuropathy exists. Ipsilateral ARTs were assessed with a stimulus including four broadband-noise or tonal activator pulses alternating with five clicks presented before, between and after the pulses. The reflex shift was defined as the difference between final and initial click responses. ARTs were measured using maximum likelihood both at low frequencies (0.8-2.8 kHz) and high (2.8-8 kHz). The median low-frequency ART was elevated by 24 dB in NHS refers compared to passes. An optimal combination of ATF and ART tests performed better than either test alone in predicting NHS outcomes, and WB tests performed better than 1-kHz tympanometry. Medial olivocochlear efferent shifts in cochlear function may influence ARs, but their presence would also be consistent with normal conductive function. Baseline clinical and WB ARTs were also compared in ipsilateral and contralateral measurements in adults.

Sound-conduction effects on distortion-product otoacoustic emission screening outcomes in newborn infants: test performance of wideband acoustic transfer functions and 1-kHz tympanometry.

OBJECTIVE: Universal newborn hearing screening (UNHS) test outcomes can be influenced by conditions affecting the sound conduction pathway, including ear canal and/or middle ear function. The purpose of this study was to evaluate the test performance of wideband (WB) acoustic transfer functions and 1-kHz tympanometry in terms of their ability to predict the status of the sound conduction pathway for ears that passed or were referred in a UNHS program. DESIGN: A distortion-product otoacoustic emission (DPOAE) test was used to determine the UNHS status of 455 infant ears (375 passed and 80 referred). WB and 1-kHz tests were performed immediately after the infant's first DPOAE test (day 1). Of the 80 infants referred on day 1, 67 infants were evaluated again after a second UNHS DPOAE test the next day (day 2). WB data were acquired under ambient and tympanometric (pressurized) ear canal conditions. Clinical decision theory analysis was used to assess the test performance of WB and 1-kHz tests in terms of their ability to classify ears that passed or were referred, using DPOAE UNHS test outcomes as the "gold standard." Specifically, performance was assessed using previously published measurement criteria and a maximum-likelihood procedure for 1-kHz tympanometry and WB measurements, respectively. RESULTS: For measurements from day 1, the highest area under the receiver operating characteristic curve was 0.87 for an ambient WB test predictor. The highest area under the receiver operating characteristic curve among several variables derived from 1-kHz tympanometry was 0.75. In general, ears that passed the DPOAE UNHS test had higher energy absorbance compared with those that were referred, indicating that infants who passed the DPOAE UNHS had a more acoustically efficient conductive pathway. CONCLUSIONS: Results showed that (1) WB tests had better performance in classifying UNHS DPOAE outcomes than 1-kHz tympanometry; (2) WB tests provide data to suggest that many UNHS referrals are a consequence of transient conditions affecting the sound conduction pathway; (3) WB data reveal changes in sound conduction during the first 2 days of life; and (4) because WB measurements used in the present study are objective and quick it may be feasible to consider implementing such measurements in conjunction with UNHS programs.

Effects of maturation on tympanometric wideband acoustic transfer functions in human infants.

Wideband acoustic transfer function (ATF) measurements of energy reflectance (ER) and admittance magnitude (|Y|) were obtained at varying static ear-canal pressures in 4-, 12-, and 27-week-old infants and young adults. Developmental changes in wideband ATF measurements varied as a function of frequency. For frequencies from 0.25 to 0.75 kHz there was as much as a 30% change in mean ER and mid |Y| with changes in static ear-canal pressure between 4 and 24 weeks of age. From 0.75 to 2 kHz, the effects of pressure produced a small number of significant differences in ER and mid |Y| with age, suggestive of a developmentally stable frequency range. Between 2 and 6 kHz, there were differential effects of pressure for the youngest infants; negative pressures caused increased ER and mid |Y| and positive pressures caused decreased ER and mid |Y|; the magnitude of this effect decreased with age. Findings from this study demonstrate developmental differences in wideband tympanometric ATF measurements in 4-, 12- and 24-week-old infants and provide additional insight on the effects of static ear-canal pressure in the young infant's ear. The maturational effects shown in the experimental data are discussed in light of known age-related anatomical changes in the developing outer and middle ear.

Wideband absorbance tympanometry using pressure sweeps: system development and results on adults with normal hearing.

A system with potential for middle-ear screening and diagnostic testing was developed for the measurement of wideband energy absorbance (EA) in the ear canal as a function of air pressure, and tested on adults with normal hearing. Using a click stimulus, the EA was measured at 60 frequencies between 0.226 and 8 kHz. Ambient-pressure results were similar to past studies. To perform tympanometry, air pressure in the ear canal was controlled automatically to sweep between -300 and 200 daPa (ascending/descending directions) using sweep speeds of approximately 75, 100, 200, and 400 daPas. Thus, the measurement time for wideband tympanometry ranged from 1.5 to 7 s and was suitable for clinical applications. A bandpass tympanogram, calculated for each ear by frequency averaging EA from 0.38 to 2 kHz, had a single-peak shape; however, its tympanometric peak pressure (TPP) shifted as a function of sweep speed and direction. EA estimated at the TPP was similar across different sweep speeds, but was higher below 2 kHz than EA measured at ambient pressure. Future studies of EA on normal ears of a different age group or on impaired ears may be compared with the adult normal baseline obtained in this study.

Detection of the acoustic stapedius reflex in infants using wideband energy reflectance and admittance.

This study examined the measurement of the contralateral acoustic stapedius reflex in six-week-old infants and adults using wideband shifts in admittance and energy reflectance (YR). The reflex activator was bandpass noise from 2,500 to 11,000 Hz presented at a maximum spectrum level of 51 dB SPL measured in the ear canal. Reflexes were detected by calculating a cross-correlation between one-twelfth-octave measurements of YR for the highest activator level and responses to lower levels. The reflex-induced shifts in YR for the infant ears were similar in pattern to adult responses but were noisy at frequencies below 1000 Hz. Infant reflexes were more successfully detected when the cross-correlation was calculated from 1000 to 8000 Hz, whereas adult reflexes were more successfully detected for a cross-correlation from 250 to 2000 Hz. This method may be useful in capturing the most robust frequency region for acoustic reflex detection across postnatal middle ear development.