An evaluation of the CARL manikin for use in "patient-free" real ear measurement: consistency and comparison to normative data.

OBJECTIVE: Simulation-based learning experiences provide low-risk opportunities for procedural training and practice in audiology. A series of real ear measurements (REM) were completed using Clinical Assistant for Research and Learning (CARL) manikins to determine expected responses and to compare to normative data. DESIGN: (1) Real-ear Unaided Response (REUR) curves were measured with one CARL and each of three ear styles. (2) Test/retest reliability was evaluated by repeating each REUR. (3) Real ear to coupler difference (RECD) values for foam-tip and custom earmolds were calculated. (4) The reliability across copies of the CARL heads was evaluated by comparing REUR measurement from one set of ears on 4 heads. STUDY SAMPLE: Four adult CARL manikins and thirty ears (5 sets of large, small, and bent). RESULTS: Within each ear category, the average difference across frequencies from one ear to the next was less than 2.5 dB with no significant individual difference more than 5.8 dB. Test/retest reliability was excellent. Typical REUR and RECD curves were created for each ear style and compared to published data on human ears. CONCLUSIONS: REM using the adult CARL head are predictable and repeatable making this simulator a good tool for audiological training.

Venting Corrections Improve the Accuracy of Coupler-Based Simulated Real-Ear Verification for Use with Adult Hearing Aid Fittings.

BACKGROUND: Hearing aid responses can be verified with the Real-Ear Aided Response (REAR). Procedures for predicting the REAR from coupler-based verification exist, but have not incorporated corrections for venting, limiting their use and validity for vented and open fittings. A commercially available system for including venting effects in simulated real-ear measurement (S-REM) has recently been developed. PURPOSE: To evaluate the accuracy of a vent-corrected S-REM for predicting the REAR across test levels, for fittings with a wide range of coupling styles including modular domes. RESEARCH DESIGN: This was a within-subject comparison study using technical measures. Retrospective file review was used to obtain previously measured REARs from 104 fittings in 52 adults and three hearing aid styles. Prospective data collection was used to re-measure each fitting at three test levels using S-REM with and without venting corrections. Comparison of differences by frequency band was performed to assess the impact of the venting correction. RESULTS: The vent model reduced low-frequency error by up to 11 dB, and the effects were consistent with the expected effects of venting in hearing aid fitting: fittings with more open dome or tip styles had a larger improvement when the vent model was added. A larger sample of fittings was obtained for dome/sleeve couplings than for custom fittings. CONCLUSIONS: The vent-corrected S-REM system evaluated in this study provides improved fitting accuracy for dome or sleeve-fitted hearing aids for adults and supports the use of vented S-REM for open fittings. Further studies to examine a representative sample of custom tip or mold fittings, and fittings for children are future directions.

Detection, Speech Recognition, Loudness, and Preference Outcomes With a Direct Drive Hearing Aid: Effects of Bandwidth.

Direct drive hearing devices, which deliver a signal directly to the middle ear by vibrating the tympanic membrane via a lens placed in contact with the umbo, are designed to provide an extension of audible bandwidth, but there are few studies of the effects of these devices on preference, speech intelligibility, and loudness. The current study is the first to compare aided speech understanding between narrow and extended bandwidth conditions for listeners with hearing loss while fitted with a direct drive hearing aid system. The study also explored the effect of bandwidth on loudness perception and investigated subjective preference for bandwidth. Fifteen adult hearing aid users with symmetrical sensorineural hearing loss participated in a prospective, within-subjects, randomized single-blind repeated-measures study. Participants wore the direct drive hearing aids for 4 to 15 weeks (average 6 weeks) prior to outcome measurement. Outcome measures were completed in various bandwidth conditions achieved by reducing the gain of the device above 5000 Hz or by filtering the stimuli. Aided detection thresholds provided evidence of amplification to 10000 Hz. A significant improvement was found in high-frequency consonant detection and recognition, as well as for speech in noise performance in the full versus narrow bandwidth conditions. Subjective loudness ratings increased with provision of the full bandwidth available; however, real-world trials showed most participants were able to wear the full bandwidth hearing aids with only small adjustments to the prescription method. The majority of participants had either no preference or a preference for the full bandwidth setting.

"Aural Patching" After Bilateral Cochlear Implantation Is Challenging for Children With Prior Long-Term Unilateral Implant Experience.

OBJECTIVES: To assess the use of "aural patching" as a strategy to potentially reduce the known persistence of aural preference in children receiving bilateral cochlear implants (CIs) with long inter-implant delays by removing the first device to increase stimulation to the second implanted side. DESIGN: Children/adolescents who received a second CI at 12.8 ± 3.5 years of age after 9.4 ± 2.9 years of unilateral CI use were asked to remove their first CI for regular periods daily (aural patching). Their compliance was monitored, and asymmetries in speech perception were measured at the end of the study period. RESULTS: Partial adherence to aural patching over the first few months of bilateral hearing use markedly declined with time. As expected, the group demonstrated asymmetries in speech perception that were not significantly affected by the limited aural patching. CONCLUSIONS: The aural patching protocol was a challenge to maintain for most children and families studied, reflecting both the expected aural preference for the first implanted ear and their challenges to reverse it.

Balancing current levels in children with bilateral cochlear implants using electrophysiological and behavioral measures.

Children have benefited from bilateral cochlear implants (CIs) over unilateral CIs despite often missing important periods in bilateral auditory development. This suggests a remarkable perceptual ability by children to "work around" abnormal changes in the auditory pathways. Nonetheless, these children rely primarily on interaural level differences as interaural timing cues are more difficult to access or detect. Mismatched levels provided to the two implants could distort interaural level cues thus compromising the benefits of bilateral CI use. We asked whether "balanced" or "centered" perception of bilateral input can be predicted by physiological or behavioral measures. Twenty-four children who had used unilateral CIs for 9.21 ± 2.66 years prior to bilateral implantation participated. "Balanced bilateral levels" were identified by responses occurring with a probability of 50% on the right side of the head and 50% on the left in a two choice lateralization task. Loudness judgments of current presented unilaterally by each implant were measured on a continuous visual scale. Maximum wave eV amplitudes were evoked unilaterally by each implant and matched amplitudes were identified. Balanced bilateral levels were predicted within 10 Clinical Units (CU) in 9 of 13 (69%) children using matched wave eV amplitudes. Bilaterally balanced levels were reasonably predicted by similar loudness judgments (<10% difference between CIs) in only 6 of 13 (46%) children. Results indicate that matching amplitudes of physiological responses can produce a balanced perception of bilateral input despite unilateral strengthening of the auditory pathways and can potentially be used clinically to provide a first approximation of balance/centered levels.

Fitting Noise Management Signal Processing Applying the American Academy of Audiology Pediatric Amplification Guideline: Verification Protocols.

BACKGROUND: Although guidelines for fitting hearing aids for children are well developed and have strong basis in evidence, specific protocols for fitting and verifying some technologies are not always available. One such technology is noise management in children's hearing aids. Children are frequently in high-level and/or noisy environments, and many options for noise management exist in modern hearing aids. Verification protocols are needed to define specific test signals and levels for use in clinical practice. PURPOSE: This work aims to (1) describe the variation in different brands of noise reduction processors in hearing aids and the verification of these processors and (2) determine whether these differences are perceived by 13 children who have hearing loss. Finally, we aimed to develop a verification protocol for use in pediatric clinical practice. STUDY SAMPLE: A set of hearing aids was tested using both clinically available test systems and a reference system, so that the impacts of noise reduction signal processing in hearing aids could be characterized for speech in a variety of background noises. A second set of hearing aids was tested across a range of audiograms and across two clinical verification systems to characterize the variance in clinical verification measurements. Finally, a set of hearing aid recordings that varied by type of noise reduction was rated for sound quality by children with hearing loss. RESULTS: Significant variation across makes and models of hearing aids was observed in both the speed of noise reduction activation and the magnitude of noise reduction. Reference measures indicate that noise-only testing may overestimate noise reduction magnitude compared to speech-in-noise testing. Variation across clinical test signals was also observed, indicating that some test signals may be more successful than others for characterization of hearing aid noise reduction. Children provided different sound quality ratings across hearing aids, and for one hearing aid rated the sound quality as higher with the noise reduction system activated. CONCLUSIONS: Implications for clinical verification systems may be that greater standardization and the use of speech-in-noise test signals may improve the quality and consistency of noise reduction verification cross clinics. A suggested clinical protocol for verification of noise management in children's hearing aids is suggested.

Perception of binaural cues develops in children who are deaf through bilateral cochlear implantation.

There are significant challenges to restoring binaural hearing to children who have been deaf from an early age. The uncoordinated and poor temporal information available from cochlear implants distorts perception of interaural timing differences normally important for sound localization and listening in noise. Moreover, binaural development can be compromised by bilateral and unilateral auditory deprivation. Here, we studied perception of both interaural level and timing differences in 79 children/adolescents using bilateral cochlear implants and 16 peers with normal hearing. They were asked on which side of their head they heard unilaterally or bilaterally presented click- or electrical pulse- trains. Interaural level cues were identified by most participants including adolescents with long periods of unilateral cochlear implant use and little bilateral implant experience. Interaural timing cues were not detected by new bilateral adolescent users, consistent with previous evidence. Evidence of binaural timing detection was, for the first time, found in children who had much longer implant experience but it was marked by poorer than normal sensitivity and abnormally strong dependence on current level differences between implants. In addition, children with prior unilateral implant use showed a higher proportion of responses to their first implanted sides than children implanted simultaneously. These data indicate that there are functional repercussions of developing binaural hearing through bilateral cochlear implants, particularly when provided sequentially; nonetheless, children have an opportunity to use these devices to hear better in noise and gain spatial hearing.

Unilateral cochlear implant use promotes normal-like loudness perception in adolescents with childhood deafness.

OBJECTIVES: Behavioral measures of cochlear implant (CI) device stimulation levels can be difficult to obtain in individuals with limited or no hearing experience. Loudness measures are particularly challenging. It would therefore be useful to have a battery of objective and behavioral measures to determine CI stimulation levels in listeners with childhood deafness. In the present study, the authors characterized loudness growth in 20 adolescents: 8 with normal hearing and 12 CI participants with pre/perilingual bilateral sensorineural hearing loss. They asked (1) do adolescent CI users with childhood deafness experience similar increases in loudness as their peers with normal hearing? and (2) can loudness be predicted by objective measures of auditory activity? The authors hypothesized that loudness perception would be significantly different between CI and normal-hearing groups and that it would correlate with objective measures. DESIGN: CI users were recruited from the Cochlear Implant Program at The Hospital for Sick Children and all had used unilateral Nucleus CIs for at least 2 years. The dynamic range for each participant was defined as the difference between the behavioral threshold and the electrically evoked stapedius reflex (ESR) threshold. Loudness growth was assessed within this range behaviorally on a continuous visual scale and objectively with physiological measures. Auditory brainstem responses (ABRs) and ESRs were recorded in both groups and electrically evoked compound action potentials (ECAPs) of the auditory nerve were recorded in addition in CI listeners. The regression line slopes of ECAP and ABR amplitude growth functions were then calculated and compared with behavioral loudness growth slopes in the upper portion (40-100%) and lower portion (0-40%) of the dynamic range. Electrical pulse stimuli (in CI users) and acoustic clicks (in normal-hearing participants) were presented within each participant's dynamic range. RESULTS: The mean dynamic range in CI listeners was more variable than in normal-hearing individuals. Despite this difference, loudness at the ESR threshold was not significantly different in CI adolescents from their normal-hearing peers, and CI users exhibited normal-like loudness growth. There was a significantly positive correlation between ECAP amplitude growth and loudness growth in CI users in the upper portion of the dynamic range, while ABR wave V amplitude growth was not related to loudness growth in either group. CONCLUSIONS: We confirmed that the ESR threshold is a good measure of comfortably loud levels in adolescents with cochlear implants and their normal-hearing peers. Adolescents using CIs show normal-like rates of loudness growth on average, despite having highly variable dynamic ranges of hearing. Individual rates of loudness growth in the upper dynamic range in CI users can be predicted by the rate of amplitude growth of the ECAP. Thus, the rate of neural recruitment with increasing CI current is important for loudness perception in pre/perilingually deaf listeners and should be considered when programming their CIs.

Three familial cases of Michel's aplasia.

Complete agenesis of the bony labyrinth, first described by Michel, represents the most severe form of inner ear defect. A search of the literature yielded only one report of this rare anomaly, affecting two siblings. Three familial cases of bilateral inner ear aplasia are reported here, and the probable inheritance pattern of this condition is discussed.