Prevalence of Self-Reported Voice Concerns and Associated Risk Markers in a Nonclinical Sample of Military Service Members.

INTRODUCTION: Difficult communication environments are common in military settings, and effective voice use can be critical to mission success. This study aimed to estimate the prevalence of self-reported voice disorders among U.S. military service members and to identify factors that contribute to their voice concerns. METHOD: A nonclinical sample of 4,123 active-duty service members was recruited across Department of Defense hearing conservation clinics. During their required annual hearing evaluation, volunteers provided responses to voice-related questions including a slightly adapted version of the Voice Handicap Index-10 (VHI-10) as part of a larger survey about communication issues. Changepoint detection was applied to age and years of service to explore cohort effects in the reporting of voice concerns. Logistic regression analyses examined multiple available factors related to communication to identify factors associated with abnormal results on the VHI-10. RESULTS: Among the respondents, 41% reported experiencing vocal hoarseness or fatigue at least several times per year, and 8.2% (n = 336) scored above the recommended abnormal cut-point value of 11 on the VHI-10. Factors independently associated with the greatest risk for self-reported voice concerns were sex (female), cadmium exposure, vocal demands (the need for a strong, clear voice), and auditory health measures (frequency of experiencing temporary threshold shifts; self-reported hearing difficulties). CONCLUSIONS: Based on self-reported voice concerns and false negative rates reported in the literature, the prevalence of dysphonia in a large sample of active-duty service members is estimated to be 11.7%, which is higher than that in the general population. Certain predictors for voice concerns were expected based on previous literature, like female sex and voice use, but frequency of temporary threshold shifts and exposure to cadmium were surprising. The strong link between voice and auditory problems has particular implications regarding the need for effective communication in high-noise military and other occupational environments.

Assessment methods for determining small changes in hearing performance over time.

Although the behavioral pure-tone threshold audiogram is considered the gold standard for quantifying hearing loss, assessment of speech understanding, especially in noise, is more relevant to quality of life but is only partly related to the audiogram. Metrics of speech understanding in noise are therefore an attractive target for assessing hearing over time. However, speech-in-noise assessments have more potential sources of variability than pure-tone threshold measures, making it a challenge to obtain results reliable enough to detect small changes in performance. This review examines the benefits and limitations of speech-understanding metrics and their application to longitudinal hearing assessment, and identifies potential sources of variability, including learning effects, differences in item difficulty, and between- and within-individual variations in effort and motivation. We conclude by recommending the integration of non-speech auditory tests, which provide information about aspects of auditory health that have reduced variability and fewer central influences than speech tests, in parallel with the traditional audiogram and speech-based assessments.

Self-Adjustment of Hearing Aid Amplification for Lower Speech Levels: Independent Ratings, Paired Comparisons, and Speech Recognition.

PURPOSE: Self-adjustment of hearing aid amplification enables wearers to customize the hearing aid output to match their preferences and could become an important tool for programming direct-to-consumer devices for people with mild-to-moderate hearing loss. One risk is that user-selected settings may provide inadequate audibility. This study assessed that risk by quantifying relationships between self-adjusted settings, subjective preferences, and speech recognition performance using speech at low levels in quiet, where achieving high speech audibility requires sufficient amplification. METHOD: Fifteen people with symmetric, mild-to-moderate sensorineural hearing loss self-adjusted hearing aid amplification while listening to speech in quiet at 45, 55, and 65 dBA. After self-adjustment, 11 participants made blinded ratings of their self-adjusted fit, their NAL-NL2 prescriptive fit, and experimenter-created fits with reduced gain. Participants completed blinded paired comparisons and sentence recognition assessments using these settings. RESULTS: The gain of self-adjusted fits showed a large range of variability between participants. On average, self-adjusted gain was similar to NAL-NL2 prescribed gain for input signals of 55 dBA and slightly greater than prescribed gain for 45-dBA signals. Speech recognition scores for NAL-NL2 fits were consistently high, and differences in speech recognition results were strongly correlated with the overall preferences obtained from paired comparisons. CONCLUSIONS: Self-adjusted fits are highly variable between individuals for low-audibility conditions. Nonetheless, self-adjusted fits are at least as satisfactory as NAL-NL2 fits, and listeners tend to disfavor settings that result in poorer speech recognition. The findings argue against concerns that self-adjustment will result in inadequate audibility compared to prescribed settings.

Evaluation of Extended-Wear Hearing Aids as a Solution for Intermittently Noise-Exposed Listeners With Hearing Loss.

OBJECTIVES: Many individuals with noise-related hearing loss continue working in environments where they are periodically exposed to high levels of noise, which increases their risk for further hearing loss. These individuals often must remove their hearing aids in operational environments because of incompatibility with the mandated personal protective equipment, thus reducing situational awareness. Extended-wear hearing aids might provide a solution for these individuals because they can be worn for weeks or months at a time, protect users from high-level noise exposures, and are compatible with communication headsets, earmuffs, and other types of personal protective equipment. The purpose of this study was to evaluate localization ability and speech understanding, feasibility of fitting and use, and acceptability in terms of comfort in a population of noise-exposed, active duty Service members. DESIGN: Participants in the study were active duty Service members who were experienced hearing aid users and were currently using standard hearing aids bilaterally. Participants were fitted with extended-wear hearing aids for up to 14 weeks. Laboratory measures included functional gain, sound localization, and speech recognition (in quiet and in noise). Performance was compared between unaided, standard hearing aids, extended-wear hearing aids, and extended-wear hearing aids combined with a tactical communication device (3M Peltor ComTac). In addition, self-perceived benefit between extended-wear hearing aids and standard hearing aids was compared. RESULTS: The extended-wear hearing aids provided more attenuation of external sound when turned off compared to standard hearing aids. Speech understanding in quiet and in noise was comparable between extended-wear hearing aids and standard hearing aids and was better when a tactical communication device was worn in addition to extended-wear hearing aids. Localization with extended-wear hearing aids was the worst, intermediate with the standard hearing aids, and the best when the ears were unaided. The extended-wear hearing aids and standard hearing aids provided similar self-perceived communication benefits relative to unaided ears. Device failure and issues with extended-wear hearing aids fit and comfort contributed to a high participant withdrawal rate. CONCLUSIONS: Overall, the hearing benefits of extended-wear hearing aids for Service members with hearing loss were comparable to those obtained with standard hearing aids, except for sound localization, which was poorer with extended-wear hearing aids. Extended-wear hearing aids provide the additional benefits of protecting the ears from high-level impulsive noise and being compatible with tactical communication and protection systems and other existing personal protective equipment and communication gear. The withdrawal rate in this study, however, suggests that extended-wear hearing aids may not be suitable for active duty Service members in locations where properly trained hearing professionals are not available to replace or re-insert extended-wear hearing aids when needed due to discomfort or device failure.

Listener Factors Explain Little Variability in Self-Adjusted Hearing Aid Gain.

Self-adjustment of hearing aid gain can provide valuable information about the gain preferences of individual listeners, but these preferences are not well understood. Listeners with mild-to-moderate hearing loss used self-adjustment to select amplification gain and compression parameters in real time on a portable touch screen device while listening in quiet and noisy backgrounds. Adjustments to gain prescribed by the National Acoustics Laboratories' non-linear fitting procedure (NAL-NL2) showed large between-subject variability. Known listener characteristics (age, gender, hearing thresholds, hearing aid experience, acceptable noise level, and external ear characteristics) and listener engagement with the self-adjustment software were examined as potential predictors of this variability. Neither listener characteristics nor time spent adjusting gain were robust predictors of gain change from NAL-NL2. Listeners with less than 2 years of hearing aid experience and who also had better hearing thresholds tended to select less gain, relative to NAL-NL2, than experienced hearing aid users who had poorer thresholds. Listener factors explained no more than 10% of the between-subject variance in deviation from NAL-NL2, suggesting that modifying prescriptive fitting formulae based on the factors examined here would be unlikely to result in amplification parameters that are similar to user-customized settings. Self-adjustment typically took less than 3 min, indicating that listeners could use comparable technology without a substantial time commitment.

Self-Adjusted Amplification Parameters Produce Large Between-Subject Variability and Preserve Speech Intelligibility.

The current study used the self-fitting algorithm to allow listeners to self-adjust hearing-aid gain or compression parameters to select gain for speech understanding in a variety of quiet and noise conditions. Thirty listeners with mild to moderate sensorineural hearing loss adjusted gain parameters in quiet and in several types of noise. Outcomes from self-adjusted gain and audiologist-fit gain indicated consistent within-subject performance but a great deal of between-subject variability. Gain selection did not strongly affect intelligibility within the range of signal-to-noise ratios tested. Implications from the findings are that individual listeners have consistent preferences for gain and may prefer gain configurations that differ greatly from National Acoustic Laboratories-based prescriptions in quiet and in noise.

Amplitude fluctuations in a masker influence lexical segmentation in cochlear implant users.

Normal-hearing listeners show masking release, or better speech understanding in a fluctuating-amplitude masker than in a steady-amplitude masker, but most cochlear implant (CI) users consistently show little or no masking release even in artificial conditions where masking release is highly anticipated. The current study examined the hypothesis that the reduced or absent masking release in CI users is due to disruption of linguistic segmentation cues. Eleven CI subjects completed a sentence keyword identification task in a steady masker and a fluctuating masker with dips timed to increase speech availability. Lexical boundary errors in their responses were categorized as consistent or inconsistent with the use of the metrical segmentation strategy (MSS). Subjects who demonstrated masking release showed greater adherence to the MSS in the fluctuating masker compared to subjects who showed little or no masking release, while both groups used metrical segmentation cues similarly in the steady masker. Based on the characteristics of the segmentation cues, the results are interpreted as evidence that CI listeners showing little or no masking release are not reliably segregating speech from competing sounds, further suggesting that one challenge faced by CI users listening in noisy environments is a reduction of reliable segmentation cues.

Identification and multiplicity of double vowels in cochlear implant users.

PURPOSE: The present study examined cochlear implant (CI) users' perception of vowels presented concurrently (i.e., double vowels) to further our understanding of auditory grouping in electric hearing. METHOD: Identification of double vowels and single vowels was measured with 10 CI subjects. Fundamental frequencies (F0s) of vowels were either 100 + 100 Hz or 100 + 300 Hz. Vowels were presented either synchronously or with a time delay. In "Double" sessions, subjects were given only double vowels. In "Double + Single" sessions, while double and single vowels were presented, subjects reported the number and identity of the vowel(s). In addition to clinical settings, stimuli were delivered via an experimental method that interleaved pulse streams of two vowels. RESULTS: Although the time delay between vowels had a large effect on identification, the effect of change in fundamental frequency (ΔF0) was modest. Enumeration was poor in general, and identification of synchronous vowels was above chance in only the Double sessions with a priori knowledge about presentation. Interleaved presentation of vowel streams provided no benefit for identification and a marginal benefit for enumeration. CONCLUSIONS: The results demonstrate the importance of episodic context for CI users. Unreliable perception of multiplicity observed in the present results suggests that auditory grouping in CIs may be driven by a schema-based process.

Sentence recognition in noise promoting or suppressing masking release by normal-hearing and cochlear-implant listeners.

Normal-hearing (NH) listeners maintain robust speech understanding in modulated noise by "glimpsing" portions of speech from a partially masked waveform--a phenomenon known as masking release (MR). Cochlear implant (CI) users, however, generally lack such resiliency. In previous studies, temporal masking of speech by noise occurred randomly, obscuring to what degree MR is attributable to the temporal overlap of speech and masker. In the present study, masker conditions were constructed to either promote (+MR) or suppress (-MR) masking release by controlling the degree of temporal overlap. Sentence recognition was measured in 14 CI subjects and 22 young-adult NH subjects. Normal-hearing subjects showed large amounts of masking release in the +MR condition and a marked difference between +MR and -MR conditions. In contrast, CI subjects demonstrated less effect of MR overall, and some displayed modulation interference as reflected by poorer performance in modulated maskers. These results suggest that the poor performance of typical CI users in noise might be accounted for by factors that extend beyond peripheral masking, such as reduced segmental boundaries between syllables or words. Encouragingly, the best CI users tested here could take advantage of masker fluctuations to better segregate the speech from the background.

Effects of stimulation configurations on place pitch discrimination in cochlear implants.

The present study aimed to examine the effect of electrode configuration, specifically monopolar (MP) or bipolar (BP) stimulation, on place pitch discrimination in cochlear implants (CIs). Twelve subjects implanted with the Nucleus Freedom device were presented with various pairs of stimulation across the electrode array, with varying degrees of distance between stimulation sites, and asked to judge the higher of the two in pitch. Each pair was presented either in the same mode or in different modes of stimulation for the within-mode or across-mode condition, respectively, at least 20 times. The result of the within-mode condition revealed that subjects, on average, were able to discriminate pitches significantly better in MP than in BP, with the sensitivity index (d') for adjacent channels of 1.2 for MP and 0.8 for BP. The result of the across-mode condition revealed that while individual variability existed, there was a strong tendency for CI subjects to perceive a higher pitch in BP stimulation than in MP for a similar site of stimulation. In other words, an MP channel needed to be shifted in a basal direction by as much as two electrodes on average to elicit a pitch comparable to that of a BP channel.