Automated Adaptive Wideband Acoustic Stapedius Reflex Thresholds in Adults With Normal Hearing and Sensorineural Hearing Loss.

OBJECTIVES: This study compared the measurement of the acoustic stapedius reflex threshold (ART) obtained using a traditional method with that obtained using an automated adaptive wideband (AAW) method. Participants included three groups of adults with normal hearing (NH), mild sensorineural hearing loss (SNHL), or moderate SNHL. The purpose of the study was to compare ARTs for the three groups and to determine which method had the best performance in detecting SNHL. DESIGN: Ipsilateral and contralateral ARTs were obtained using 0.5, 1, and 2 kHz tonal activators, and broadband noise (BBN) activators on a traditional admittance system (Clinical) at tympanometric peak pressures (TPP) and on an experimental wideband system using an AAW method at both ambient pressure and TPP. ART data previously reported for 39 NH adults with a mean age of 47.7 years were compared with data for 25 participants with mild SNHL with a mean age of 63.8 years, and 20 participants with moderate SNHL with a mean age of 65.7 years. Differences in ARTs between the normal-hearing and SNHL groups for the three methods were examined using a General Linear Model Repeated-Measures test. A receiver operating characteristic curve (ROC) analysis was also used to determine the ability of an ART test to detect SNHL. RESULTS: For the 0.5 kHz activator condition, there were no significant group mean differences in ART between NH and SNHL groups for either ipsilateral or contralateral activator presentation modes for the Clinical or AAW methods. There were significant group mean differences for the 1 and 2 kHz tonal activators and BBN activator for both ipsilateral and contralateral modes with greater differences in ART between groups for the AAW method than the Clinical method. In these conditions, the mean ART was lower for the AAW tests relative to the Clinical test. The greatest difference between groups was for the ipsilateral AAW tests for the comparison of NH with moderate SNHL for the BBN activator. This difference was approximately 20 dB for the AAW tests and 8 dB for the Clinical test. The ROC analysis showed that the area under the ROC curve (AUC) increased with the frequency of the activator stimulus and with the degree of hearing loss and was maximal for the BBN activator for both the AAW and Clinical methods for both ipsilateral and contralateral presentations. CONCLUSIONS: For ipsilateral and contralateral ART tests for activator frequencies above 0.5 kHz and BBN, listeners with SNHL generally had elevated ARTs compared with those with NH. The AAW method resulted in greater differences between SNHL groups and NH than the Clinical method. The AUC for detecting SNHL also increased with activator frequency and degree of hearing loss and was greatest for the BBN activator for the AAW method in both the ambient and TPP conditions. The results are encouraging for the use of an AAW ART method for the assessment of individuals with SNHL.

Automated Adaptive Wideband Acoustic Reflex Threshold Estimation in Normal-hearing Adults.

OBJECTIVES: Acoustic stapedius reflex threshold (ART) tests are included in a standard clinical acoustic immittance test battery as an objective cross-check with behavioral results and to help identify site of lesion. In traditional clinical test batteries, middle-ear admittance of a 226 Hz probe is estimated using ear-canal measurements in the presence of a reflex-activating stimulus. In the wideband (WB) acoustic immittance ART test used in this study, the pure-tone probe is replaced by a WB probe stimulus and changes in absorbed power are estimated using ear-canal measurements in the presence of the activator. The ART is defined as the lowest level at which a criterion change in admittance (clinical) or absorbed power (WB) is observed in the presence of the activator. In the present study, ARTs were obtained in adults with normal hearing using the clinical, manual method and with a new WB automated adaptive threshold detection method. It was hypothesized that the WB test would result in lower ARTs than the clinical test because reflex-related changes in power absorbance could be observed across multiple frequency bands in the WB test compared with a single frequency in the traditional test. DESIGN: Data were collected in a prospective research design. ARTs were obtained in ipsilateral and contralateral conditions using 500, 1000, 2000 Hz, and broadband noise (BBN) activators on a clinical system and on an experimental WB system. The bandwidth of the BBN activator was 125 to 4000 Hz on the clinical system and 200 to 8000 Hz on the wideband system. ARTs were estimated at both tympanometric peak pressure (TPP) and ambient pressure on the WB system. Data were collected in both ears of 39 adults (21 males) of mean age 47.7 years (range 23-72 years). Differences in ARTs among the three threshold estimation methods (clinical, WB at TPP, WB at ambient) were examined using the general linear model repeated measures test in SPSS. Post-hoc pairwise comparisons were completed with Bonferroni correction for multiple comparisons. Statistical significance was defined as p < 0.05 for all analyses. RESULTS: ARTs obtained on the WB system at TPP and ambient pressure were significantly lower than obtained on the clinical system. ARTs obtained on the WB system at TPP were significantly higher than at ambient pressure in the 500 and 2000 Hz ipsilateral conditions. CONCLUSIONS: WB automated adaptive ARTs in normal-hearing adults were lower than for clinical methods when measured at TPP and ambient pressure. Lower presentation levels required to estimate ART in the WB test may be more tolerable to patients. Patients with ARTs that are not present at the maximum level of a traditional reflex test may have present ARTs with a WB ART test, which may reduce the need to refer for additional testing for possible retrocochlear involvement. Automation of the test may allow clinicians more time to attend to the other requisite tasks of a hearing evaluation and make the system useful for telehealth applications.

Effects of Otosclerosis on Middle Ear Function Assessed With Wideband Absorbance and Absorbed Power.

OBJECTIVE: Wideband absorbance and absorbed power were evaluated in a group of subjects with surgically confirmed otosclerosis (Oto group), mean age 51.6 years. This is the first use of absorbed power in the assessment of middle ear disorders. Results were compared with control data from two groups of adults, one with normal hearing (NH group) mean age of 31 years, and one that was age- and sex-matched with the Oto group and had sensorineural hearing loss (SNHL group). The goal was to assess group differences using absorbance and absorbed power, to determine test performance in detecting otosclerosis, and to evaluate preoperative and postoperative test results. DESIGN: Audiometric and wideband tests were performed over frequencies up to 8 kHz. The three groups were compared on wideband tests using analysis of variance to assess group mean differences. Receiver operating characteristic (ROC) curve analysis was also used to assess test accuracy at classifying ears as belonging to the Oto or control groups using the area under the ROC curve (AUC). A longitudinal design was used to compare preoperative and postoperative results at 3 and 6 months. RESULTS: There were significant mean differences in the wideband parameters between the Oto and control groups with generally lower absorbance and absorbed power for the Oto group at ambient and tympanometric peak pressure (TPP) depending on frequency. The SNHL group had more significant differences with the Oto group than did the NH group in the high frequencies for absorbed power at ambient pressure and tympanometric absorbed power at TPP, as well as for the tympanometric tails. The greatest accuracy for classifying ears as being in the Oto group or a control group was for absorbed power at ambient pressure at 0.71 kHz with an AUC of 0.81 comparing the Oto and NH groups. The greatest accuracy for an absorbance measure was for the comparison between the Oto and NH groups for the peak-to-negative tail condition with an AUC of 0.78. In contrast, the accuracy for classifying ears into the control or Oto groups for static acoustic admittance at 226 Hz was near chance performance, which is consistent with previous findings. There were significant mean differences between preoperative and postoperative tests for absorbance and absorbed power. CONCLUSIONS: Consistent with previous studies, wideband absorbance showed better sensitivity for detecting the effects of otosclerosis on middle ear function than static acoustic admittance at 226 Hz. This study showed that wideband absorbed power is similarly sensitive and may perform even better in some instances than absorbance at classifying ears as having otosclerosis. The use of a group that was age- and sex-matched to the Oto group generally resulted in greater differences between groups in the high frequencies for absorbed power, suggesting that age-related norms in adults may be useful for the wideband clinical applications. Absorbance and absorbed power appear useful for monitoring changes in middle ear function following surgery for otosclerosis.

Home Hearing Test: Within-Subjects Threshold Variability.

BACKGROUND: The Home Hearing Test (HHT) is an automated pure-tone threshold test that obtains an air conduction audiogram at five test frequencies. It was developed to provide increased access to hearing testing and support home telehealth programs. PURPOSE: Test and retest thresholds for 1000-Hz stimuli were analyzed to determine intrasubject variability from two independent data sets. RESEARCH DESIGN: Prospective, repeated measures. STUDY SAMPLE: In the Veterans Affairs (VA) study, results from 26 subjects 44 to 88 years of age (mean = 65) recruited from the Nashville VA audiology clinic were analyzed. Subjects were required to have a Windows PC in the home and were self-reported to be comfortable with using computers. Two subjects had normal hearing, and 24 had hearing losses of various severities and configurations. The National Center for Rehabilitative Auditory Research (NCRAR) sample included 100 subjects (68 males; 32 females) with a complaint of hearing difficulty recruited from the local community and Veteran population. Subjects ranged in age from 32 to 87 years (mean = 63.7 years). They were tested in a quiet room at the NCRAR. DATA COLLECTION AND ANALYSIS: Subjects in the VA study were provided kits for installing HHT on their home computers. HHT was installed on a computer at NCRAR to test subjects in the NCRAR study. HHT obtains a five-frequency air conduction audiogram with a retest of 1000 Hz in both ears. Only the 1000-Hz test-retest results are analyzed in this report. Six statistical measures of test-retest variability are reported. RESULTS: Test and retest thresholds were highly correlated in both studies (r ≥ 0.96). Test-retest differences were within ±5 dB ≥92% of the time in the two studies. Standard deviations of absolute test-retest difference were ≤3.5 dB in the two studies. CONCLUSIONS: Intrasubject variability is comparable to that obtained with manual testing by audiologists in sound-treated test rooms.

Optimizing Clinical Interpretation of Distortion Product Otoacoustic Emissions in Infants.

OBJECTIVES: The purpose of this study was to analyze distortion product otoacoustic emission (DPOAE) level and signal to noise ratio in a group of infants from birth to 4 months of age to optimize prediction of hearing status. DPOAEs from infants with normal hearing (NH) and hearing loss (HL) were used to predict the presence of conductive HL (CHL), sensorineural HL (SNHL), and mixed HL (MHL). Wideband ambient absorbance was also measured and compared among the HL types. DESIGN: This is a prospective, longitudinal study of 279 infants with verified NH and HL, including conductive, sensorineural, and mixed types that were enrolled from a well-baby nursery and two neonatal intensive care units in Cincinnati, Ohio. At approximately 1 month of age, DPOAEs (1-8 kHz), wideband absorbance (0.25-8 kHz), and air and bone conduction diagnostic tone burst auditory brainstem response (0.5-4 kHz) thresholds were measured. Hearing status was verified at approximately 9 months of age with visual reinforcement audiometry (0.5-4 kHz). Auditory brainstem response air conduction thresholds were used to assign infants to an NH or HL group, and the efficacy of DPOAE data to classify ears as NH or HL was analyzed using receiver operating characteristic (ROC) curves. Two summary statistics of the ROC curve were calculated: the area under the ROC curve and the point of symmetry on the curve at which the sensitivity and specificity were equal. DPOAE level and signal to noise ratio cutoff values were defined at each frequency as the symmetry point on their respective ROC curve, and DPOAE results were combined across frequency in a multifrequency analysis to predict the presence of HL. RESULTS: Single-frequency test performance of DPOAEs was best at mid to high frequencies (3-8 kHz) with intermediate performance at 1.5 and 2 kHz and chance performance at 1 kHz. Infants with a conductive component to their HL (CHL and MHL combined) displayed significantly lower ambient absorbance values than the NH group. No differences in ambient absorbance were found between the NH and SNHL groups. Multifrequency analysis resulted in the best prediction of HL for the SNHL/MHL group with poorer sensitivity values when infants with CHL were included. CONCLUSIONS: Clinical interpretation of DPOAEs in infants can be improved by using age-appropriate normative ranges and optimized cutoff values. DPOAE interpretation is most predictive at higher F2 test frequencies in young infants (2-8 kHz) due to poor test performance at 1 to 1.5 kHz. Multifrequency rules can be used to improve sensitivity while balancing specificity. Last, a sensitive middle ear measure such as wideband absorbance should be included in the test battery to assess possibility of a conductive component to the HL.

Longitudinal Development of Distortion Product Otoacoustic Emissions in Infants With Normal Hearing.

OBJECTIVES: The purpose of this study was to describe normal characteristics of distortion product otoacoustic emission (DPOAE) signal and noise level in a group of newborns and infants with normal hearing followed longitudinally from birth to 15 months of age. DESIGN: This is a prospective, longitudinal study of 231 infants who passed newborn hearing screening and were verified to have normal hearing. Infants were enrolled from a well-baby nursery and two neonatal intensive care units (NICUs) in Cincinnati, OH. Normal hearing was confirmed with threshold auditory brainstem response and visual reinforcement audiometry. DPOAEs were measured in up to four study visits over the first year after birth. Stimulus frequencies f1 and f2 were used with f2/f1 = 1.22, and the DPOAE was recorded at frequency 2f1-f2. A longitudinal repeated-measure linear mixed model design was used to study changes in DPOAE level and noise level as related to age, middle ear transfer, race, and NICU history. RESULTS: Significant changes in the DPOAE and noise levels occurred from birth to 12 months of age. DPOAE levels were the highest at 1 month of age. The largest decrease in DPOAE level occurred between 1 and 5 months of age in the mid to high frequencies (2 to 8 kHz) with minimal changes occurring between 6, 9, and 12 months of age. The decrease in DPOAE level was significantly related to a decrease in wideband absorbance at the same f2 frequencies. DPOAE noise level increased only slightly with age over the first year with the highest noise levels in the 12-month-old age range. Minor, nonsystematic effects for NICU history, race, and gestational age at birth were found, thus these results were generalizable to commonly seen clinical populations. CONCLUSIONS: DPOAE levels were related to wideband middle ear absorbance changes in this large sample of infants confirmed to have normal hearing at auditory brainstem response and visual reinforcement audiometry testing. This normative database can be used to evaluate clinical results from birth to 1 year of age. The distributions of DPOAE level and signal to noise ratio data reported herein across frequency and age in normal-hearing infants who were healthy or had NICU histories may be helpful to detect the presence of hearing loss in infants.

Chirp-Evoked Otoacoustic Emissions and Middle Ear Absorbance for Monitoring Ototoxicity in Cystic Fibrosis Patients.

OBJECTIVES: The goal of this study was to investigate the use of transient-evoked otoacoustic emissions (TEOAEs) and middle ear absorbance measurements to monitor auditory function in patients with cystic fibrosis (CF) receiving ototoxic medications. TEOAEs were elicited with a chirp stimulus using an extended bandwidth (0.71 to 8 kHz) to measure cochlear function at higher frequencies than traditional TEOAEs. Absorbance over a wide bandwidth (0.25 to 8 kHz) provides information on middle ear function. The combination of these time-efficient measurements has the potential to identify early signs of ototoxic hearing loss. DESIGN: A longitudinal study design was used to monitor the hearing of 91 patients with CF (median age = 25 years; age range = 15 to 63 years) who received known ototoxic medications (e.g., tobramycin) to prevent or treat bacterial lung infections. Results were compared to 37 normally hearing young adults (median age = 32.5 years; age range = 18 to 65 years) without a history of CF or similar treatments. Clinical testing included 226-Hz tympanometry, pure-tone air-conduction threshold testing from 0.25 to 16 kHz and bone conduction from 0.25 to 4 kHz. Experimental testing included wideband absorbance at ambient and tympanometric peak pressure and TEOAEs in three stimulus conditions: at ambient pressure and at tympanometric peak pressure using a chirp stimulus with constant incident pressure level across frequency and at ambient pressure using a chirp stimulus with constant absorbed sound power across frequency. RESULTS: At the initial visit, behavioral audiometric results indicated that 76 of the 157 ears (48%) from patients with CF had normal hearing, whereas 81 of these ears (52%) had sensorineural hearing loss for at least one frequency. Seven ears from four patients had a confirmed behavioral change in hearing threshold for ≥3 visits during study participation. Receiver operating characteristic curve analyses demonstrated that all three TEOAE conditions were useful for distinguishing CF ears with normal hearing from ears with sensorineural hearing loss, with an area under the receiver operating characteristic curve values ranging from 0.78 to 0.92 across methods for frequency bands from 2.8 to 8 kHz. Case studies are presented to illustrate the relationship between changes in audiometric thresholds, TEOAEs, and absorbance across study visits. Absorbance measures permitted identification of potential middle ear dysfunction at 5.7 kHz in an ear that exhibited a temporary hearing loss. CONCLUSIONS: The joint use of TEOAEs and absorbance has the potential to explain fluctuations in audiometric thresholds due to changes in cochlear function, middle ear function, or both. These findings are encouraging for the joint use of TEOAE and wideband absorbance objective tests for monitoring ototoxicity, particularly, in patients who may be too ill for behavioral hearing tests. Additional longitudinal studies are needed in a larger number of CF patients receiving ototoxic drugs to further evaluate the clinical utility of these measures in an ototoxic monitoring program.

Assessing Sensorineural Hearing Loss Using Various Transient-Evoked Otoacoustic Emission Stimulus Conditions.

OBJECTIVES: An important clinical application of transient-evoked otoacoustic emissions (TEOAEs) is to evaluate cochlear outer hair cell function for the purpose of detecting sensorineural hearing loss (SNHL). Double-evoked TEOAEs were measured using a chirp stimulus, in which the stimuli had an extended frequency range compared to clinical tests. The present study compared TEOAEs recorded using an unweighted stimulus presented at either ambient pressure or tympanometric peak pressure (TPP) in the ear canal and TEOAEs recorded using a power-weighted stimulus at ambient pressure. The unweighted stimulus had approximately constant incident pressure magnitude across frequency, and the power-weighted stimulus had approximately constant absorbed sound power across frequency. The objective of this study was to compare TEOAEs from 0.79 to 8 kHz using these three stimulus conditions in adults to assess test performance in classifying ears as having either normal hearing or SNHL. DESIGN: Measurements were completed on 87 adult participants. Eligible participants had either normal hearing (N = 40; M F = 16 24; mean age = 30 years) or SNHL (N = 47; M F = 20 27; mean age = 58 years), and normal middle ear function as defined by standard clinical criteria for 226-Hz tympanometry. Clinical audiometry, immittance, and an experimental wideband test battery, which included reflectance and TEOAE tests presented for 1-min durations, were completed for each ear on all participants. All tests were then repeated 1 to 2 months later. TEOAEs were measured by presenting the stimulus in the three stimulus conditions. TEOAE data were analyzed in each hearing group in terms of the half-octave-averaged signal to noise ratio (SNR) and the coherence synchrony measure (CSM) at frequencies between 1 and 8 kHz. The test-retest reliability of these measures was calculated. The area under the receiver operating characteristic curve (AUC) was measured at audiometric frequencies between 1 and 8 kHz to determine TEOAE test performance in distinguishing SNHL from normal hearing. RESULTS: Mean TEOAE SNR was ≥8.7 dB for normal-hearing ears and ≤6 dB for SNHL ears for all three stimulus conditions across all frequencies. Mean test-retest reliability of TEOAE SNR was ≤4.3 dB for both hearing groups across all frequencies, although it was generally less (≤3.5 dB) for lower frequencies (1 to 4 kHz). AUCs were between 0.85 and 0.94 for all three TEOAE conditions at all frequencies, except for the ambient TEOAE condition at 2 kHz (0.82) and for all TEOAE conditions at 5.7 kHz with AUCs between 0.78 and 0.81. Power-weighted TEOAE AUCs were significantly higher (p < 0.05) than ambient TEOAE AUCs at 2 and 2.8 kHz, as was the TPP TEOAE AUC at 2.8 kHz when using CSM as the classifier variable. CONCLUSIONS: TEOAEs evaluated in an ambient condition, at TPP and in a power-weighted stimulus condition, had good test performance in identifying ears with SNHL based on SNR and CSM in the frequency range from 1 to 8 kHz and showed good test-retest reliability. Power-weighted TEOAEs showed the best test performance at 2 and 2.8 kHz. These findings are encouraging as a potential objective clinical tool to identify patients with cochlear hearing loss.

Normative Wideband Reflectance, Equivalent Admittance at the Tympanic Membrane, and Acoustic Stapedius Reflex Threshold in Adults.

OBJECTIVES: Wideband acoustic immittance (WAI) measures such as pressure reflectance, parameterized by absorbance and group delay, equivalent admittance at the tympanic membrane (TM), and acoustic stapedius reflex threshold (ASRT) describe middle ear function across a wide frequency range, compared with traditional tests employing a single frequency. The objective of this study was to obtain normative data using these tests for a group of normal-hearing adults and investigate test-retest reliability using a longitudinal design. DESIGN: A longitudinal prospective design was used to obtain normative test and retest data on clinical and WAI measures. Subjects were 13 males and 20 females (mean age = 26 years). Inclusion criteria included normal audiometry and clinical immittance. Subjects were tested on two separate visits approximately 1 month apart. Reflectance and equivalent admittance at the TM were measured from 0.25 to 8.0 kHz under three conditions: at ambient pressure in the ear canal and with pressure sweeps from positive to negative pressure (downswept) and negative to positive pressure (upswept). Equivalent admittance at the TM was calculated using admittance measurements at the probe tip that were adjusted using a model of sound transmission in the ear canal and acoustic estimates of ear-canal area and length. Wideband ASRTs were measured at tympanometric peak pressure (TPP) derived from the average TPP of downswept and upswept tympanograms. Descriptive statistics were obtained for all WAI responses, and wideband and clinical ASRTs were compared. RESULTS: Mean absorbance at ambient pressure and TPP demonstrated a broad band-pass pattern typical of previous studies. Test-retest differences were lower for absorbance at TPP for the downswept method compared with ambient pressure at frequencies between 1.0 and 1.26 kHz. Mean tympanometric peak-to-tail differences for absorbance were greatest around 1.0 to 2.0 kHz and similar for positive and negative tails. Mean group delay at ambient pressure and at TPP were greatest between 0.32 and 0.6 kHz at 200 to 300 µsec, reduced at frequencies between 0.8 and 1.5 kHz, and increased above 1.5 kHz to around 150 µsec. Mean equivalent admittance at the TM had a lower level for the ambient method than at TPP for both sweep directions below 1.2 kHz, but the difference between methods was only statistically significant for the comparison between the ambient method and TPP for the upswept tympanogram. Mean equivalent admittance phase was positive at all frequencies. Test-retest reliability of the equivalent admittance level ranged from 1 to 3 dB at frequencies below 1.0 kHz, but increased to 8 to 9 dB at higher frequencies. The mean wideband ASRT for an ipsilateral broadband noise activator was 12 dB lower than the clinical ASRT, but had poorer reliability. CONCLUSIONS: Normative data for the WAI test battery revealed minor differences for results at ambient pressure compared with tympanometric methods at TPP for reflectance, group delay, and equivalent admittance level at the TM for subjects with middle ear pressure within ±100 daPa. Test-retest reliability was better for absorbance at TPP for the downswept tympanogram compared with ambient pressure at frequencies around 1.0 kHz. Large peak-to-tail differences in absorbance combined with good reliability at frequencies between about 0.7 and 3.0 kHz suggest that this may be a sensitive frequency range for interpreting absorbance at TPP. The mean wideband ipsilateral ASRT was lower than the clinical ASRT, consistent with previous studies. Results are promising for the use of a wideband test battery to evaluate middle ear function.

Comparing otoacoustic emissions evoked by chirp transients with constant absorbed sound power and constant incident pressure magnitude.

Human ear-canal properties of transient acoustic stimuli are contrasted that utilize measured ear-canal pressures in conjunction with measured acoustic pressure reflectance and admittance. These data are referenced to the tip of a probe snugly inserted into the ear canal. Promising procedures to calibrate across frequency include stimuli with controlled levels of incident pressure magnitude, absorbed sound power, and forward pressure magnitude. An equivalent pressure at the eardrum is calculated from these measured data using a transmission-line model of ear-canal acoustics parameterized by acoustically estimated ear-canal area at the probe tip and length between the probe tip and eardrum. Chirp stimuli with constant incident pressure magnitude and constant absorbed sound power across frequency were generated to elicit transient-evoked otoacoustic emissions (TEOAEs), which were measured in normal-hearing adult ears from 0.7 to 8 kHz. TEOAE stimuli had similar peak-to-peak equivalent sound pressure levels across calibration conditions. Frequency-domain TEOAEs were compared using signal level, signal-to-noise ratio (SNR), coherence synchrony modulus (CSM), group delay, and group spread. Time-domain TEOAEs were compared using SNR, CSM, instantaneous frequency and instantaneous bandwidth. Stimuli with constant incident pressure magnitude or constant absorbed sound power across frequency produce generally similar TEOAEs up to 8 kHz.

Wideband acoustic immittance in children with Down syndrome: prediction of middle-ear dysfunction, conductive hearing loss and patent PE tubes.

OBJECTIVE: The purpose of this study was to evaluate pressurised wideband acoustic immittance (WAI) tests in children with Down syndrome (DS) and in typically developing children (TD) for prediction of conductive hearing loss (CHL) and patency of pressure equalising tubes (PETs). DESIGN: Audiologic diagnosis was determined by audiometry in combination with distortion-product otoacoustic emissions, 0.226 kHz tympanometry and otoscopy. WAI results were compared for ears within diagnostic categories (Normal, CHL and PET) and between groups (TD and DS). STUDY SAMPLE: Children with DS (n = 40; mean age 6.4 years), and TD children (n = 48; mean age 5.1 years) were included. RESULTS: Wideband absorbance was significantly lower at 1-4 kHz in ears with CHL compared to NH for both TD and DS groups. In ears with patent PETs, wideband absorbance and group delay (GD) were larger than in ears without PETs between 0.25 and 1.5 kHz. Wideband absorbance tests were performed similarly for prediction of CHL and patent PETs in TD and DS groups. CONCLUSIONS: Wideband absorbance and GD revealed specific patterns in both TD children and those with DS that can assist in detection of the presence of significant CHL, assess the patency of PETs, and provide frequency-specific information in the audiometric range.

Comparisons of transient evoked otoacoustic emissions using chirp and click stimuli.

Transient-evoked otoacoustic emission (TEOAE) responses (0.7-8 kHz) were measured in normal-hearing adult ears using click stimuli and chirps whose local frequency increased or decreased linearly with time over the stimulus duration. Chirp stimuli were created by allpass filtering a click with relatively constant incident pressure level over frequency. Chirp TEOAEs were analyzed as a nonlinear residual signal by inverse allpass filtering each chirp response into an equivalent click response. Multi-window spectral and temporal averaging reduced noise levels compared to a single-window average. Mean TEOAE levels using click and chirp stimuli were similar with respect to their standard errors in adult ears. TEOAE group delay, group spread, instantaneous frequency, and instantaneous bandwidth were similar overall for chirp and click conditions, except for small differences showing nonlinear interactions differing across stimulus conditions. These results support the theory of a similar generation mechanism on the basilar membrane for both click and chirp conditions based on coherent reflection within the tonotopic region. TEOAE temporal fine structure was invariant across changes in stimulus level, which is analogous to the intensity invariance of click-evoked basilar-membrane displacement data.

Air and Bone Conduction Click and Tone-Burst Auditory Brainstem Thresholds Using Kalman Adaptive Processing in Nonsedated Normal-Hearing Infants.

OBJECTIVES: To study normative thresholds and latencies for click and tone-burst auditory brainstem response (TB-ABR) for air and bone conduction in normal infants and those discharged from neonatal intensive care units, who passed newborn hearing screening and follow-up distortion product otoacoustic emission. An evoked potential system (Vivosonic Integrity) that incorporates Bluetooth electrical isolation and Kalman-weighted adaptive processing to improve signal to noise ratios was employed for this study. Results were compared with other published data. DESIGN: One hundred forty-five infants who passed two-stage hearing screening with transient-evoked otoacoustic emission or automated auditory brainstem response were assessed with clicks at 70 dB nHL and threshold TB-ABR. Tone bursts at frequencies between 500 and 4000 Hz were used for air and bone conduction auditory brainstem response testing using a specified staircase threshold search to establish threshold levels and wave V peak latencies. RESULTS: Median air conduction hearing thresholds using TB-ABR ranged from 0 to 20 dB nHL, depending on stimulus frequency. Median bone conduction thresholds were 10 dB nHL across all frequencies, and median air-bone gaps were 0 dB across all frequencies. There was no significant threshold difference between left and right ears and no significant relationship between thresholds and hearing loss risk factors, ethnicity, or gender. Older age was related to decreased latency for air conduction. Compared with previous studies, mean air conduction thresholds were found at slightly lower (better) levels, while bone conduction levels were better at 2000 Hz and higher at 500 Hz. Latency values were longer at 500 Hz than previous studies using other instrumentation. Sleep state did not affect air or bone conduction thresholds. CONCLUSIONS: This study demonstrated slightly better wave V thresholds for air conduction than previous infant studies. The differences found in the present study, while statistically significant, were within the test step size of 10 dB. This suggests that threshold responses obtained using the Kalman weighting software were within the range of other published studies using traditional signal averaging, given step-size limitations. Thresholds were not adversely affected by variable sleep states.

Procedures for ambient-pressure and tympanometric tests of aural acoustic reflectance and admittance in human infants and adults.

Procedures are described to measure acoustic reflectance and admittance in human adult and infant ears at frequencies from 0.2 to 8 kHz. Transfer functions were measured at ambient pressure in the ear canal, and as down- or up-swept tympanograms. Acoustically estimated ear-canal area was used to calculate ear reflectance, which was parameterized by absorbance and group delay over all frequencies (and pressures), with substantial data reduction for tympanograms. Admittance measured at the probe tip in adults was transformed into an equivalent admittance at the eardrum using a transmission-line model for an ear canal with specified area and ear-canal length. Ear-canal length was estimated from group delay around the frequency above 2 kHz of minimum absorbance. Illustrative measurements in ears with normal function are described for an adult, and two infants at 1 month of age with normal hearing and a conductive hearing loss. The sensitivity of this equivalent eardrum admittance was calculated for varying estimates of area and length. Infant-ear patterns of absorbance peaks aligned in frequency with dips in group delay were explained by a model of resonant canal-wall mobility. Procedures will be applied in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function.

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.

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.

Prediction of conductive hearing loss using wideband acoustic immittance.

The purpose of this article was to review the effectiveness of wideband acoustic immittance (WAI) and tympanometry in detecting conductive hearing loss (CHL). Eight studies were included that measured CHL through air-and bone-conducted thresholds in at least a portion of their participants. One study included infants, three studies included children, one study included older children and adults, and three studies included adults. WAI identified CHL well in all populations. In infants and children, WAI in several single-frequency bands identified CHL with equal accuracy to measures of middle ear admittance using clinical tympanometry with a single probe tone (1000 Hz for infants; 226 Hz for children and adults). When WAI was combined across frequency bands, it identified CHL superior to traditional, single-frequency tympanometry. Only two studies used WAI tympanometry, which assesses the outer/middle ear across both frequency and introduced air pressure, and differing results were reported as to whether introducing pressure into the ear canal provides better identification of CHL. In general, WAI appears to be a promising clinical tool, and further investigation is warranted.

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.

Fundamental Concepts for Assessment and Interpretation of Wideband Acoustic Immittance Measurements.

Assessment of middle ear impedance using noninvasive electroacoustic measurements has undergone successive developments since its first clinical application in the 1940s, and gained widespread adoption since the 1970s in the form of 226-Hz tympanometry, and applications in multifrequency tympanometry. More recently, wideband acoustic immittance (WAI) is allowing unprecedented assessments of the middle ear acoustic mechanics thanks to the ability to record responses over a wide range of frequencies. The purpose of this article is to present fundamental concepts for the assessment and interpretation of wideband measures, including a review of acoustic impedance and its relation to the mass, stiffness, and resistance components of the middle ear. Additionally, an understanding of the middle ear transfer function reveals the relationship between impedance and middle-ear gain as a function of frequency. Wideband power absorbance, a WAI measure, quantifies the efficiency of sound conduction through the middle ear over a wide range of frequencies, and can serve as an analogous clinical measure to the transfer function. The interpretation of absorbance measures in ears with or without a conductive condition using absorbance measured at ambient pressure and pressurized conditions (wideband tympanometry) is described using clinical case examples. This article serves as an introduction to the fundamental principles of WAI measurements.