Extended-wear hearing aids (EWHAs) are small broadband analog amplification devices placed deeply enough in the ear canal to preserve most of the cues in the head-related transfer function. However, little is known about how EWHAs affect localization accuracy for normal hearing threshold (NHT) listeners. In this study, eight NHT participants were fitted with EWHAs and localized broadband sounds of different durations (250 ms and 4 s) and stimulus intensities (40, 50, 60, 70, and 80 dBA) in a spherical speaker array. When the EWHAs were in the active mode, localization accuracy was only slightly degraded relative to open-ear performance. However, when the EWHAs were turned off, localization performance was substantially degraded even at the highest stimulus intensities. An electro-acoustical evaluation of the EWHAs showed minimal effects of dynamic range compression on the signals and good preservation of the signal pattern for vertical polar sound localization. Between-study comparisons suggest that EWHA active mode localization accuracy is favorable compared to conventional active earplugs, and EWHA passive mode localization accuracy is comparable to conventional passive earplugs. These results suggest that the deep-insertion analog design of the EWHA is generally better at preserving localization accuracy of NHT listeners than conventional earplug devices.

Simpson et al. [JASA 129(4), 2489, (2011)] found that localization of a target presented in a simultaneous masker improved when, on a trial-by-trial basis, a preview of the masking stimulus was presented at the location of the upcoming masker. Subsequent research revealed that this improvement resulted solely from cueing the location of the masker (i.e., cueing spectro-temporal properties of the masker provided no additional benefit). In the present study, we examined the degree to which the benefit of cueing masker location depended on the modality in which this cue was provided. In separate blocks of trials, the location of the masker was cued auditorily, visually (LED activated at the masker location) and audio-visually, and compared to performance in a no-cue baseline. The results revealed a substantial (∼10 dB) benefit of cueing the masker auditorily over the no-cue condition, consistent with previous results. Importantly, there was also a substantial (albeit smaller) benefit of a visual cue (∼6 dB). Performance with a bimodal cue was no different than performance with an auditory cue. Thus, although hearing a sound from the upcoming masker location was most effective, the ability to effectively cue space crossmodally suggests that the spatial information itself is most critical.

Conventional hearing protection devices (HPDs) work well in predictable noise environments where it is practical to put them on prior to exposure and remove them after. However, some noise environments are characterized by long periods of relative quiet that are unpredictably interrupted by brief periods of hazardous noise. These environments make it difficult to ensure that HPDs are worn when exposure to hazardous levels occurs. One possible solution is the extended-wear hearing aid (EWHA), a hearing aid that completely blocks the ear canal and can remain in the ear for months at a time. Previous research has shown that the EWHA can provide protection from impulse noise without significantly interfering with detection and localization of environmental sounds. At that time, the major drawback of the EWHA was that once it was removed it could only be re-inserted by an audiologist. This limitation has been addressed by the development of a self-insertion tool that allows users to remove and re-insert the EWHA as desired. We will discuss the potential advantages of using the EWHA as an HPD, with an emphasis on situations where the EWHA could be used to reduce noise exposure without modifying the current commercially available device.

Disability is an important and often overlooked component of diversity. Individuals with disabilities bring a rare perspective to science, technology, engineering, mathematics, and medicine (STEMM) because of their unique experiences approaching complex issues related to health and disability, navigating the healthcare system, creatively solving problems unfamiliar to many individuals without disabilities, managing time and resources that are limited by physical or mental constraints, and advocating for themselves and others in the disabled community. Yet, individuals with disabilities are underrepresented in STEMM. Professional organizations can address this underrepresentation by recruiting individuals with disabilities for leadership opportunities, easing financial burdens, providing equal access, fostering peer-mentor groups, and establishing a culture of equity and inclusion spanning all facets of diversity. We are a group of deaf and hard-of-hearing (D/HH) engineers, scientists, and clinicians, most of whom are active in clinical practice and/or auditory research. We have worked within our professional societies to improve access and inclusion for D/HH individuals and others with disabilities. We describe how different models of disability inform our understanding of disability as a form of diversity. We address heterogeneity within disabled communities, including intersectionality between disability and other forms of diversity. We highlight how the Association for Research in Otolaryngology has supported our efforts to reduce ableism and promote access and inclusion for D/HH individuals. We also discuss future directions and challenges. The tools and approaches discussed here can be applied by other professional organizations to include individuals with all forms of diversity in STEMM.

Most speech perception studies assume that the talkers are speaking to the subject, but little is known regarding subject ability to monitor exchanges between interlocutors (i.e., “eavesdrop”). The current study measured subject ability to monitor two concurrent, artificially generated “conversations” using phrases from the Coordinate Response Measure corpus. Individual conversations consisted of a “prompt” phrase of the form: “Ready [call sign] go to [color]-[number] now” and a “response” phrase of the form: “[same call sign] going to [color]-[number]”. A color and/or number prompt-response mismatch occurred within a conversation on 50% of trials. The listener was asked to identify whether a mismatch took place and, if so, identify in which of the two conversations the mismatch occurred. The (virtual) conversations were either co-located or spatially separated (±15°, ±90°). All talkers were of the same gender, or competing prompters and competing responders were of different genders. Group-mean performance ranged from about 65–80% correct in mismatch detection, and about 70%–85% correct in call sign identification (for mistake-ID correct trials). Performance improved when competing talkers were separated to ±15 deg in space, and/or in gender. This suggests that, on average, listeners can follow simultaneous conversations over time, particularly when competing talkers differ in pitch or space.

Hearing-protection devices (HPD) are critical to hearing health in hazardous noise environments, but can be detrimental to job effectiveness and safety when degrading a wearer’s sound localization accuracy. Understanding specifically how localization is disrupted by HPDs is critical for mitigating the deleterious effects of HPDs on situation awareness. This study attempts to better quantify the effects of the degradations by predicting horizontal sound localization. A 360 deg horizontal array with 10 deg between-speaker spacing is used to collect head-related transfer functions (HRTFs) and to measure localization [ANSI/ASA S3.71] for the different conditions (open-ear, passive plugs, and both passive and active muffs). Our model attempts to select the response location that was most likely to have elicited the observed stimulus for the trial, by comparing narrow-band statistics between prior knowledge (“templates”) and trial observations. Bone conduction related noise is added, and the degree to which the priors are “device-related” (i.e., based on HRTFs captured for the device) or “open ear” related is varied. Results are discussed in terms of two potential mechanisms: (1) the wrong location is chosen due to a prior/template mismatch in percent device-related and (2) multiple response locations are viable because cue variability is reduced between locations compared to within.

Objectives: Single-sided deafness cochlear-implant (SSD-CI) listeners and bilateral cochlear-implant (BI-CI) listeners gain near-normal levels of head-shadow benefit but limited binaural benefits. One possible reason for these limited binaural benefits is that cochlear places of stimulation tend to be mismatched between the ears. SSD-CI and BI-CI patients might benefit from a binaural fitting that reallocates frequencies to reduce interaural place mismatch. However, this approach could reduce monaural speech recognition and head-shadow benefit by excluding low- or high-frequency information from one ear. This study examined how much frequency information can be excluded from a CI signal in the poorer-hearing ear without reducing head-shadow benefits and how these outcomes are influenced by interaural asymmetry in monaural speech recognition. Design: Speech-recognition thresholds for sentences in speech-shaped noise were measured for 6 adult SSD-CI listeners, 12 BI-CI listeners, and 9 normal-hearing listeners presented with vocoder simulations. Stimuli were presented using nonindividualized in-the-ear or behind-the-ear head-related impulse-response simulations with speech presented from a 70° azimuth (poorer-hearing side) and noise from 70° (better-hearing side), thereby yielding a better signal-to-noise ratio (SNR) at the poorer-hearing ear. Head-shadow benefit was computed as the improvement in bilateral speech-recognition thresholds gained from enabling the CI in the poorer-hearing, better-SNR ear. High- or low-pass filtering was systematically applied to the head-related impulse-response–filtered stimuli presented to the poorer-hearing ear. For the SSD-CI listeners and SSD-vocoder simulations, only high-pass filtering was applied, because the CI frequency allocation would never need to be adjusted downward to frequency-match the ears. For the BI-CI listeners and BI-vocoder simulations, both low and high pass filtering were applied. The normal-hearing listeners were tested with two levels of performance to examine the effect of interaural asymmetry in monaural speech recognition (vocoder synthesis-filter slopes: 5 or 20 dB/octave). Results: Mean head-shadow benefit was smaller for the SSD-CI listeners (~7 dB) than for the BI-CI listeners (~14 dB). For SSD-CI listeners, frequencies <1236 Hz could be excluded; for BI-CI listeners, frequencies <886 or >3814 Hz could be excluded from the poorer-hearing ear without reducing head-shadow benefit. Bilateral performance showed greater immunity to filtering than monaural performance, with gradual changes in performance as a function of filter cutoff. Real and vocoder-simulated CI users with larger interaural asymmetry in monaural performance had less head-shadow benefit. Conclusions: The “exclusion frequency” ranges that could be removed without diminishing head-shadow benefit are interpreted in terms of low importance in the speech intelligibility index and a small head-shadow magnitude at low frequencies. Although groups and individuals with greater performance asymmetry gained less head-shadow benefit, the magnitudes of these factors did not predict the exclusion frequency range. Overall, these data suggest that for many SSD-CI and BI-CI listeners, the frequency allocation for the poorer-ear CI can be shifted substantially without sacrificing head-shadow benefit, at least for energetic maskers. Considering the two ears together as a single system may allow greater flexibility in discarding redundant frequency content from a CI in one ear when considering bilateral programming solutions aimed at reducing interaural frequency mismatch.

The extended-wear hearing aid (EWHA) is a hearing assistive device that combines a low-power analog amplification circuit with a soft biocompatible foam plug that allows it to remain in the ear canal for several months at a time without replacement. EWHAs fit snugly in the ear canal and are not vented and so produce insertion losses comparable to a passive earplug when inserted into the ear canal with the active circuitry turned off. However, EWHAs are not marketed as hearing protection devices, and other than a general warning to users that the device will have impaired auditory awareness when the device is inserted in the "off" mode, relatively little has been reported about the attenuation characteristics of EWHAs. In this study, commercially-available EWHAs were evaluated using the ANSI standard procedures for measuring hearing protector attenuation in impulse noise [ANSI (2010). S1242-2010, Methods for the Measurement of Insertion Loss of Hearing Protective Devices in Continuous or Impulsive Noise Using Microphone-In-Real-Ear or Acoustic Text Fixture Procedures (American National Standards Institute, New York)] and in continuous noise [ANSI (2006). S12.6, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors (American National Standards Institute, New York)]. Attenuation values were also measured in double and triple protection conditions that combined EWHAs with traditional earplugs and earmuffs. The results show that properly-fit EWHAs can provide passive attenuation comparable to conventional passive earplugs, which may make it possible to use them to provide persistent protection from intermittent noise sources.

For single-sided deafness cochlear-implant (SSD-CI) listeners, different peripheral representations for electric versus acoustic stimulation, combined with interaural frequency mismatch, might limit the ability to perceive bilaterally presented speech as a single voice. The assessment of binaural fusion often relies on subjective report, which requires listeners to have some understanding of the perceptual phenomenon of object formation. Two experiments explored whether binaural fusion could instead be assessed using judgments of the number of voices in a mixture. In an SSD-CI simulation, normal-hearing listeners were presented with one or two "diotic" voices (i.e., unprocessed in one ear and noise-vocoded in the other) in a mixture with additional monaural voices. In experiment 1, listeners reported how many voices they heard. Listeners generally counted the diotic speech as two separate voices, regardless of interaural frequency mismatch. In experiment 2, listeners identified which of two mixtures contained diotic speech. Listeners performed significantly better with interaurally frequency-matched than with frequency-mismatched stimuli. These contrasting results suggest that listeners experienced partial fusion: not enough to count the diotic speech as one voice, but enough to detect its presence. The diotic-speech detection task (experiment 2) might provide a tool to evaluate fusion and optimize frequency mapping for SSD-CI patients.

Virtual localization experiments have demonstrated that Head Related Transfer Functions measured a few millimeters inside a blocked ear canal can produce localization performance approaching what is measured in the free field. This suggests that an earplug inserted entirely inside the ear canal should be able to preserve normal localization performance so long as the stimulus is loud enough to overcome any insertion loss in the device at all frequencies. In this study, localization performance of normal-hearing listeners was measured with the Lyric extended wear hearing aid, both in active mode (where it acted like an electronic pass-through earplug) and in passive mode (where it acted like a passive hearing protector). In an active mode, localization accuracy approached the open-ear condition. However, under the passive condition, localization was much worse than with the open ear even at high stimulus levels where the full spectrum should have been audible. This result suggests there may be fundamental limitations on localization accuracy with passive hearing protection that are unrelated to the directionality of the HRTF. [The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of the Army/Air Force, Department of Defense, or U.S. Government.]

Sabin et al. (2005) measured localization accuracy for 250-ms broadband noises that varied in location along a spherical surface, and varied in stimulus level, from 0 to 60 dB above the detection threshold. They found that, for lower stimulus levels, responses tended to be biased towards lower elevations and to the front, and were more accurate at higher stimulus levels. Whereas Sabin et al. (2005) randomized level and location between trials, the current study fixed location and increased level until a correct response was given (or the 80 dB SPL limit was reached). Our initial level was 12.5 dB SPL, and our step size 2.5 dB SPL. Responses tended to be biased towards lower vertical elevations and to the front at low stimulus levels, and be more accurate at higher levels, consistent with Sabin et al. The percentage of front/back errors was generally greater for locations in the rear hemifield relative to those in the frontal hemifield, and for locations at higher elevations relative to locations at lower elevations. Audibility analysis, performed using a KEMAR manikin, showed that localization errors tended to decrease the most when audible bandwidth increased at the acoustically better ear.

Localization accuracy for a target presented in a simultaneous masker, whose location varies randomly from trial to trial, improves when a preview of the masker location is provided (by playing a sound from that location) prior to the target + masker interval (i.e., a pre-trial cue) [B. Simpson, Ph.D. dissertation (Wright State University, 2011)]. One explanation is that knowing the masker location allows a listener to establish a “spatial attention filter” at the masker location. The present study compares the effect of such a pre-trial cue to the case in which the cue comes after the target + masker interval (post-trial cueing). That is, the cue is presented either 500 ms prior to the onset of a 60-ms, 100-Hz click-train target embedded in a 60-ms broadband masker, or 500 ms subsequent to the offset of the target + masker stimulus. The data indicate that both cue types lead to similar improvements in performance over the no-cue condition, with the greatest improvement from cueing (~6 dB) seen for localization in the left/right dimension. While these data are roughly consistent with previous results, they cannot be explained by a simple spatial filter hypothesis.

OBJECTIVES:"Channel-linked" and "multi-band" front-end automatic gain control (AGC) were examined as alternatives to single-band, channel-unlinked AGC in simulated bilateral cochlear implant (CI) processing. In channel-linked AGC, the same gain control signal was applied to the input signals to both of the two CIs ("channels"). In multi-band AGC, gain control acted independently on each of a number of narrow frequency regions per channel.DESIGN:Speech intelligibility performance was measured with a single target (to the left, at -15 or -30°) and a single, symmetrically-opposed masker (to the right) at a signal-to-noise ratio (SNR) of -2 decibels. Binaural sentence intelligibility was measured as a function of whether channel linking was present and of the number of AGC bands. Analysis of variance was performed to assess condition effects on percent correct across the two spatial arrangements, both at a high and a low AGC threshold. Acoustic analysis was conducted to compare postcompressed better-ear SNR, interaural differences, and monaural within-band envelope levels across processing conditions.RESULTS:Analyses of variance indicated significant main effects of both channel linking and number of bands at low threshold, and of channel linking at high threshold. These improvements were accompanied by several acoustic changes. Linked AGC produced a more favorable better-ear SNR and better preserved broadband interaural level difference statistics, but did not reduce dynamic range as much as unlinked AGC. Multi-band AGC sometimes improved better-ear SNR statistics and always improved broadband interaural level difference statistics whenever the AGC channels were unlinked. Multi-band AGC produced output envelope levels that were higher than single-band AGC.CONCLUSIONS:These results favor strategies that incorporate channel-linked AGC and multi-band AGC for bilateral CIs. Linked AGC aids speech intelligibility in spatially separated speech, but reduces the degree to which dynamic range is compressed. Combining multi-band and channel-linked AGC offsets the potential impact of diminished dynamic range with linked AGC without sacrificing the intelligibility gains observed with linked AGC.

Just-noticeable differences (JNDs) in interaural time delay (ITD), interaural level difference (ILD), and interaural cross-correlation (ICC) were measured with low- and high-frequency noise bands over multiple sessions for 10 normal-hearing (NH) and 11 hearing-impaired (HI) listeners. Individual subject thresholds tended to improve with training then stabilize. Measured JNDs varied over these experienced listeners, for both subject groups and all tasks. Group JNDs were seldom predictable from hearing level. Individual listeners' JNDs were highly correlated across frequency for each task and group, except for ICC in the HI listeners. Further, ITD JNDs almost always significantly correlated with ILD JNDs within a group. Finally, although the ICC JNDs always significantly correlated with the ITD or ILD JNDs for the NH listeners, they often did not for the HI listeners. These findings suggest that little information about binaural sensitivity is added for NH listeners with multiple ITD, ILD, and ICC measures. For HI listeners, however, while ITD and ILD measures are well correlated, information is added with ICC measures. In general, the results suggest that less information is added with JND measures for NH listeners (15 significant correlations) than for HI listeners (six significant correlations).

Auditory training studies have varied in degree-of-similarity between the training and testing conditions. Some focused testing on the trained task (e.g., Sweetow and Henderson Sabes, 2007), while others addressed whether the training effects generalize to other tasks. The current study used speech and non-speech stimuli to explore how much training in a specific analytical listening task would generalize to performance improvements for another. Naïve listeners participated. Percent correct was measured as a function of signal-to-noise ratio (SNR) in pre- and post-tests with the “multiple-bursts same” (MBS) paradigm (Kidd et al., 1994) and the speech-target/speech-masker Coordinate Response Measure (CRM) paradigm. There were three training groups in a between-groups design: 1) training in a masked speech identification task (the CRM) with the competitors varying in f0 separation (Darwin et al., 2003); 2) training in the MBS task with the protected-region (frequency region with no maskers) bandwidth around the target varying; and 3) no training. Preliminary data describe individual-subject variability in pre-test performance and indicate performance improvements with auditory training. The degree of generalization will be explored for the trained sub-groups. 1) Int J. Audiol. 46. 374. 2) J. Acoust. Soc. Am. 114, 2913. 3) J. Acoust. Soc. Am. 95, 962.

Bilateral cochlear implants (CIs) are becoming increasingly common. It is hoped for bilateral CI users that audibility in quiet will be complemented by performance benefits in everyday binaural listening tasks, like location-identification of a speech talker presented amid other talkers. While normal-hearing (NH) listeners have typically performed well in such kinds of tasks, bilateral CI users have performed poorly. It is possible that, for bilateral CI users, better performances can be attained through a re-thinking of device signal-processing strategies. In particular, we are interested in evaluating alternatives to single-channel independent compression, as is typically applied at the automatic gain control (AGC) stage. Specifically, we test the hypothesis that for simulated bilateral CI users (listeners with both NH and hearing impairments, HI), lower rms-error in a masked lateralization task will be achieved for multi-channel AGC and linked AGC, than for single-channel independent AGC, with and without pre-emphasis filtering, and for low and high compression thresholds. Preliminary data suggest a lower rms-error for linked compression than for independent compression, in conjunction with no detrimental effect of multi-channel compression. These data support the possibility of linked AGC with multi-channel AGC as an alternative to independent AGC in bilateral CI listening.