Effects of coordinated compression and pinna compensation features on horizontal localization performance in hearing aid users.

BACKGROUND: Hearing-impaired listeners localize sounds better unaided than aided. Wide dynamic range compression circuits operating independently at each ear in bilateral fittings, and microphone positions of different hearing aid styles, have been cited as a reason. Two hearing aid features, inter-ear coordinated compression (IE) and pinna compensation (PC), were developed to mitigate the compromised aided localization performance. PURPOSE: This study examined the effect of IE and PC on aided localization performance in the horizontal plane with hearing-impaired listeners. RESEARCH DESIGN: A single-blind, repeated-measures design was used. STUDY SAMPLE: A total of 10 experienced hearing aid users with bilaterally symmetrical sensorineural hearing loss who had previously participated in localization training were evaluated. DATA COLLECTION AND ANALYSIS: Localization performance was measured using 12 loudspeakers spaced 30° apart on the horizontal plane. Aided performance was evaluated using a behind-the-ear hearing aid at four settings: omnidirectional microphone (Omni), Omni microphone with the PC feature, Omni microphone with IE, and Omni microphone with the PC feature and IE together. In addition, unaided localization performance was measured. RESULTS: Significant improvement in the localization accuracy was measured for sounds arriving from the back when comparing the PC with the Omni conditions. The use of IE reduced the magnitude of errors for some listeners for sounds originating from ±90°. The average reduction in the errors was 7.3°. CONCLUSIONS: This study confirmed that the use of the PC feature improved localization for sounds arriving from behind the listener. The use of IE may improve localization for some listeners for sounds arriving from the sides.

Amplification for listeners with a moderately severe high-frequency hearing loss.

BACKGROUND: Some evidence exists to support the use of an extended bandwidth (EBW) for those with a relatively mild to moderate degree of hearing loss. The use of frequency lowering is suggested for those with a severe/profound degree of hearing loss. The amplification option for those with a moderately severe hearing loss in the high frequencies is less clear. This study compared three amplification options for listeners with a moderately severe hearing loss in the high frequencies. PURPOSE: The efficacy of three amplification options-limited bandwidth to 4000 Hz, EBW, and frequency transposition-were evaluated for listeners with a moderately severe, high-frequency hearing loss. RESEARCH DESIGN: The experiment used a factorial repeated-measures design. STUDY SAMPLE: A total of 13 adults with bilateral hearing loss of 50-70 dB HL at 4000 Hz served as test participants. DATA COLLECTION AND ANALYSIS: The participants rated the sound quality of birdsongs and music when aided with the amplification options. Speech perception in quiet was measured at 50 dB SPL and 68 dB SPL input levels. The participants also completed a questionnaire on the best amplification option to use in different real-life environments during a 2 wk, take-home trial. The data were analyzed with repeated-measures analysis of variance. RESULTS: The findings showed that more listeners preferred the EBW for home use but that the frequency transposition was the least preferred. In addition, the performance of the EBW was better than that of the limited bandwidth in speech recognition but similar to that of the frequency transposition. CONCLUSIONS: The results supported the fitting of an EBW as the better choice for this group of listeners.

Evaluation of a localization training program for hearing impaired listeners.

OBJECTIVE: To evaluate the effectiveness of a home-based and a laboratory-based localization training program. DESIGN: This study examined the effectiveness of a localization training program on improving the localization ability of 15 participants with a mild-to-moderately severe hearing loss. These participants had worn the study hearing aids in a previous study. The training consisted of laboratory-based training and home-based training. The participants were divided into three groups: a control group, a group that performed the laboratory training first followed by the home training, and a group that completed the home training first followed by the laboratory training. The participants were evaluated before any training (baseline), at 2 weeks, 1 month, 2 months, and 3 months after baseline testing. All training was completed by the second month. The participants only wore the study hearing aids between the second month and the third month. Localization testing and laboratory training were conducted in a sound-treated room with a 360 degree, 12 loudspeaker array. There were three stimuli each randomly presented three times from each loudspeaker (nine test items from each loudspeaker) for a total of 108 items on each test or training trial. The stimuli, including a continuous noise, a telephone ring, and a speech passage "Search for the sound from this speaker" were high-pass filtered above 2000 Hz. The test stimuli had a duration of 300 ms, whereas the training stimuli had five durations (3 s, 2 s, 1 s, 500 ms, and 300 ms) and four back attenuation (-8, -4, -2, and 0 dB re: front presentation) values. All stimuli were presented at 30 dB SL or the most comfortable listening level of the participants. Each participant completed 6 to 8, 2 hr laboratory-based training within a month. The home training required a two-loudspeaker computer system using 30 different sounds of various durations (5) by attenuation (4) combinations. The participants were required to use the home training program for 30 min per day, 5 days per week for 4 weeks. RESULTS: Localization data were evaluated using a 30 degree error criterion. There was a significant difference in localization scores for sounds that originated from the back between baseline and 3 months for the two groups that received training. The performance of the control group remained the same across the 3 month period. Generalization to other stimuli and in the unaided condition was also seen. There were no significant differences in localization performance from other directions between baseline and 3 months. These results indicated that the training program was effective in improving the localization skills of these listeners under the current test set-up. CONCLUSIONS: The current study demonstrated that hearing aid wearers can be trained on their front/back localization skills using either laboratory-based or home-based training program. The effectiveness of the training was generalized to other acoustic stimuli and the unaided conditions when the stimulus levels were fixed.

Effects of a transient noise reduction algorithm on speech understanding, subjective preference, and preferred gain.

BACKGROUND: Today's compression hearing aids with noise reduction systems may not manage transient noises effectively because of the short duration of these sounds compared to the onset times of the compressors and/or noise reduction algorithms. PURPOSE: The current study was designed to evaluate the effect of a transient noise reduction (TNR) algorithm on listening comfort, speech intelligibility in quiet, and preferred wearer gain in the presence of transients. RESEARCH DESIGN: A single-blinded, repeated-measures design was used. STUDY SAMPLE: Thirteen experienced hearing aid users with bilaterally symmetrical (≤7.5 dB) sensorineural hearing loss participated in the study. RESULTS: Speech identification in quiet (no transient noise) was identical between the TNR On and the TNR Off conditions. The participants showed subjective preference for the TNR algorithm when "comfortable listening" was used as the criterion. Participants preferred less gain than the default prescription in the presence of transient noise sounds. However, the preferred gain was 2.9 dB higher when the TNR was activated than when it was deactivated. This translated to 12.1% improvement in phoneme identification over the TNR Off condition for soft speech. CONCLUSIONS: This study demonstrated that the use of the TNR algorithm would not negatively affect speech identification. The results also suggested that this algorithm may improve listening comfort in the presence of transient noise sounds and ensure consistent use of prescribed gain. Such an algorithm may ensure more consistent audibility across listening environments.

Evaluation of a pinna compensation algorithm for sound localization and speech perception in noise.

PURPOSE: This study was designed to evaluate the effect of a pinna compensation (PC) algorithm on localization performance in the horizontal plane and speech intelligibility in noise. METHOD: Nine and 18 experienced hearing aid users with bilaterally symmetrical sensorineural hearing loss participated in the localization study and the speech-in-noise study, respectively. Performance was evaluated unaided, aided with a behind-the-ear (BTE) hearing aid with an omnidirectional microphone (Omni), and aided with the same hearing aid with the PC algorithm (Omni+PC). Localization performance was measured using 12 loudspeakers spaced 30° apart on a horizontal plane. Speech-in-noise performance was measured with speech presented from 0° or 180°. A single-blinded, repeated measures design was used. RESULTS: Significant improvement in localization accuracy was found when comparing the Omni+PC condition to the Omni condition. Also, the Omni+PC condition improved the signal-to-noise ratio by 2.4 dB when compared to the Omni condition when speech was presented from the front in a diffuse noise background. CONCLUSION: Use of the PC algorithm improved localization on the horizontal plane and speech-in-noise performance. These results support use of the PC algorithm in BTE hearing aid fittings.

Efficacy of a reverse cardioid directional microphone.

BACKGROUND: Directional microphones have been shown to improve a listener's ability to communicate in noise by improving the signal to noise ratio. However, their efficacy may be questioned in situations where the listener needs to understand speech originating from the back. PURPOSE: The goal of the study was to examine the performance of a directional microphone mode that has an automatic reverse cardioid polar pattern. RESEARCH DESIGN: A single-blinded, factorial repeated-measures design was used to study the effect of microphone modes (reverse cardioid, omnidirectional, and front hypercardioid) and stimulus azimuths (front and back) on three outcome variables (aided thresholds, nonsense syllable identification in quiet, and sentence recognition in noise). STUDY SAMPLE: Twenty adults with a mild-to-severe bilaterally symmetrical (±5 dB) sensorineural hearing loss participated. INTERVENTION: Audibility in quiet was evaluated by obtaining aided sound field thresholds and speech identification at an input level of 50 dB SPL presented at 0 and 180° azimuths. In addition, speech understanding in noise was also assessed with the Hearing In Noise Test (HINT) sentences presented at both azimuths (0 and 180°) with a diffuse noise. DATA COLLECTION AND ANALYSIS: Repeated-measures analyses of variance (ANOVAs) were conducted to examine the effects of microphone mode (omnidirectional, front hypercardioid, reverse cardioid) and stimulus azimuth (0°, 180°) on aided thresholds, nonsense syllable identification, and HINT performance. RESULTS: Results with the reverse cardioid directional microphone in both quiet conditions were similar to the omnidirectional microphone. The results of the reverse cardioid microphone in noise were significantly better than the omnidirectional microphone and front hypercardioid microphone when speech was presented from the back (p < 0.001). CONCLUSIONS: These results support the possible benefits of a reverse cardioid directional microphone when used in specific listening situations.

Development of the ORCA nonsense syllable test.

OBJECTIVES: Many new processing features in hearing aids have their primary effects on information located in the high frequencies. Speech perception tests that are optimized for evaluating high-frequency processing are needed to adequately study its effects on speech identification. The goal of the current research was to develop a medium for evaluating the effects of high-frequency processing in hearing aids. DESIGN: A list of 115 consonant-vowel-consonant-vowel-consonant nonsense syllables with American English consonants in all word positions was created in an open-set phoneme identification format. The source material was spoken by a male and a female speaker. A custom computer program was developed for administration of the test and automatic analysis of the test results. Nine normal-hearing listeners were employed in the collection of the normative data. The test was presented to the listeners in quiet (at 68 dB SPL), in noise at five signal-to-noise ratios (SNRs; -10, -5, 0, 5, and 10), and in a low-pass filter condition with cutoff frequencies at 500, 1000, 1500, 2000, and 4000 Hz. The data were examined to evaluate the psychometric properties of the test for different phoneme positions and phoneme classes. In addition, a shortened version of the test was developed based on the data from normal-hearing listeners. The test-retest reliability was verified at 0 dB SNR. The full and shortened versions of the test were repeated in 10 hearing-impaired listeners at their most comfortable listening level in quiet and in noise at various SNRs. RESULTS: The availability of high-frequency output was verified with acoustic analysis. The performance intensity functions for both versions of the test (i.e., male and female speakers) showed expected monotonic growth with SNR and cutoff frequencies. High reliability was seen between test and retest identification scores in normal-hearing and hearing-impaired listeners. CONCLUSIONS: The current nonsense syllable test provided a reliable and efficient means for phoneme identification testing.

Subjective and objective evaluation of noise management algorithms.

PURPOSE: To measure the subjective and objective improvement of speech intelligibility in noise offered by a commercial hearing aid that uses a fully adaptive directional microphone and a noise reduction algorithm that optimizes the Speech Intelligibility Index (SII). RESEARCH DESIGN: Comparison of results on the Hearing in Noise Test (HINT) and the Acceptable Noise Level task (ANL). STUDY SAMPLE: Eighteen participants with varying configurations of sensorineural hearing loss. RESULTS: Both the directional microphone and the noise reduction algorithm improved the speech-in-noise performance of the participants. The benefits reported were higher for the directional microphone than the noise reduction algorithm. A moderate correlation was noted between the benefits measured on the HINT and the ANL for the directional microphone condition, the noise reduction condition, and the directional microphone plus noise reduction conditions. CONCLUSIONS: These results suggest that the directional microphone and the SII-based noise reduction algorithm may improve the SNR of the listening environments, and both the HINT and the ANL may be used to study their benefits.

Efficacy of linear frequency transposition on consonant identification in quiet and in noise.

BACKGROUND: Frequency transposition has gained renewed interest in recent years. This type of processing takes sounds in the unaidable high-frequency region and moves them to the lower frequency region. One concern is that the transposed sounds mask or distort the original low-frequency sounds and lead to a poorer performance. On the other hand, experience with transposition may allow the listeners to relearn the new auditory percepts and benefit from transposition. PURPOSE: The current study was designed to examine the effect of linear frequency transposition on consonant identification in quiet (50 dB SPL and 68 dB SPL) and in noise at three intervals--the initial fit, after one month of use (along with auditory training), and a further one month of use (without directed training) of transposition. RESEARCH DESIGN: A single-blind, factorial repeated-measures design was used to study the effect of test conditions (three) and hearing aid setting/time interval (four) on consonant identification. STUDY SAMPLE: Eight adults with a severe-to-profound high-frequency sensorineural hearing loss participated. INTERVENTION: Participants were fit with the Widex m4-m behind-the-ear hearing aids binaurally in the frequency transposition mode, and their speech scores were measured initially. They wore the hearing aids home for one month and were instructed to complete a self-paced "bottom-up" training regimen. They returned after the training, and their speech performance was measured. They wore the hearing aids home for another month, but they were not instructed to complete any auditory training. Their speech performance was again measured at the end of the two-month trial. DATA COLLECTION AND ANALYSIS: Consonant performance was measured with a nonsense syllable test (ORCA-NST) that was developed at this facility (Office of Research in Clinical Amplification [Widex]). The test conditions included testing in quiet at 50 dB SPL and 68 dB SPL, and at 68 dB SPL in noise (SNR [signal-to-noise ratio] = +5). The hearing aid conditions included no transposition at initial fit (V1), transposition at initial fit (V2), transposition at one month post-fit (V3), and transposition at 2 months post-fit (V4). Identification scores were analyzed for each individual phoneme and phonemic class. Repeated-measures ANOVA were conducted using SPSS software to examine significant differences. RESULTS: For all test conditions (50 dB SPL in quiet, 68 dB SPL in quiet, and 68 dB SPL in noise), a statistically significant difference (p < 0.05 level) was reached between the transposition condition measured at two months postfitting and the initial fitting (with and without transposition) for fricatives only. The difference between transposition and the no-transposition conditions at the 50 dB SPL condition was also significant for the initial and one-month intervals. Analysis of individual phonemes showed a decrease in the number of confusions and an increase in the number of correct identification over time. CONCLUSIONS: Linear frequency transposition improved fricative identification over time. Proper candidate selection with appropriate training is necessary to fully realize the potential benefit of this type of processing.

Comparison of vent effects between a solid earmold and a hollow earmold.

BACKGROUND: Hollow earmolds have become a popular type of earmold used in thin-tube, microsize hearing aid fittings. It is desirable for clinicians to be familiar with their characteristics and limitations. PURPOSE: This investigation compared the effects of vent diameter between a traditional solid earmold and a hollow earmold that is used in modern thin-tube hearing aid fittings. RESEARCH DESIGN: A single-blind, 2 x 4 factorial design was used. STUDY SAMPLE: Eight adults with a high-frequency hearing loss participated. INTERVENTION: Custom earmolds for use with thin-tube hearing aids were made for each participant. Two types of earmolds were made: a solid earmold with a traditional vent length and a hollow earmold where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. DATA COLLECTION AND ANALYSIS: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probe-microphone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. RESULTS: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. CONCLUSIONS: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects.

Stress shield: a model of police resiliency.

This paper discusses the development of a new model of police officer resiliency. Following Antonovsky's definition of resilience, the model is built on the view that the resilience of a person or group reflects the extent to which they can call upon their psychological and physical resources and competencies in ways that allow them to render challenging events coherent, manageable, and meaningful. The model posits that a police officer's capacity to render challenging experiences meaningful, coherent, and manageable reflects the interaction of person, team, and organizational factors. The paper argues that a model that encompasses these factors can be developed using theories drawn from the literatures of occupational health and empowerment. The development of the model is also informed by the need to ensure that it can accommodate the importance of learning from past experiences to build resilience in ways that increase officers' capacity to adapt to future risk and uncertainty. By building on recent empirical research, this paper outlines a new multi-level model of resilience and adaptive capacity. The Stress Shield model of resilience integrates person, team and organizational factors to provide a proactive framework for developing and sustaining police officer resilience.

Personal amplification for school-age children with auditory processing disorders.

BACKGROUND: Children with auditory processing disorders (APD) are described to have a signal-to-noise ratio (SNR) difficulty. Frequency-modulated (FM) systems have been reported to improve this situation. Yet the use of personal amplification that may be more portable has not been attempted. PURPOSE: To determine whether personal amplification would result in improvement in speech-in-noise performances (attentiveness and speech recognition) and daily functioning in children with diagnosed APD. In addition, the desired hearing aid features (such as required gain, directional microphone and noise reduction, and open-ear fitting) are examined. RESEARCH DESIGN: A single-blind, longitudinal descriptive study in which subjects served as their own control in various hearing aid conditions. STUDY SAMPLE: Fourteen normal hearing children who had a diagnosis of APD and who were between the ages of 7 and 11 participated. INTERVENTION: All subjects wore bilateral, mild-gain, behind-the-ear, wide dynamic range compression hearing aids fitted in an open-ear mode. Gain on the hearing aids was adjusted to provide approximately 10 dB of insertion gain for conversational input. Directional microphone and noise reduction were used on the hearing aids. Subjects wore the hearing aids home and were encouraged to use them as much as possible in their daily environments (school, home, and social activities). Subjects were seen four times: an initial visit where hearing aids were fitted, then visits at 2 weeks, 3 months, and 6 months after the initial fitting. The majority of the testing was completed during these final three visits. DATA COLLECTION AND ANALYSIS: The children were evaluated on the Northwestern University word-list (NU-6) and the Auditory Continuous Performance Test (ACPT) in noise at most visits. The hearing aids were evaluated in the omnidirectional microphone mode only, omnidirectional microphone with noise reduction (NR) mode, and directional microphone with NR mode. The children's parents and teachers were asked to complete the Children's Auditory Processing Performance Scale (CHAPS) questionnaire both before and at the end of the study. RESULTS: The results showed that the use of hearing aids in the omnidirectional microphone mode alone did not improve speech identification in noise over the unaided condition. However, the inclusion of the NR algorithm and directional microphones improved speech understanding in noise. Amplification reduced the number of errors on the ACPT and improved several areas on the CHAPS; however, the results were not statistically significant. CONCLUSIONS: The use of mild-gain, open-ear fitting hearing aids with a directional microphone and noise reduction algorithm may be attempted on some children with APD on a trial basis.

Performance of a fully adaptive directional microphone to signals presented from various azimuths.

The signal-to-noise ratio advantage of a directional microphone is achieved by reducing the sensitivity of the microphone to sounds from the sides and back. A fully adaptive directional microphone (one that automatically switches between an omnidirectional mode and various directional polar patterns) may allow the achievement of signal-to-noise (SNR) improvement with minimal loss on audibility to sounds that originate from the sides and back. To demonstrate such possibilities, this study compared the soundfield aided thresholds, speech in quiet at different input levels, and speech in noise performance of 17 hearing-impaired participants under three microphone modes (omnidirectional, fixed hypercardioid, and fully [or automatic] adaptive) as the stimuli were presented from 0 degrees to 180 degrees in 45 degrees intervals. The results showed a significant azimuth effect only with the fixed directional microphone. In quiet, the fully adaptive microphone performed similarly as the omnidirectional microphone at all frequencies, input levels, and azimuths. In noise, the fully adaptive microphone achieved similar SNR improvement as the fixed directional microphone. Clinical implications of the results of this study were discussed.

Real-world performance of a reverse-horn vent.

The present study compared differences in subjective and objective performance in completely-in-the-canal (CIC) hearing aids with conventional uniform 1.5 mm parallel vents and another with a reverse horn vent where the diameter increased from 1.5 mm on the lateral faceplate to 3 mm on the medial opening of the hearing aid. Nine hearing-impaired persons with a high-frequency hearing loss participated. The test battery included unaided in situ thresholds, amount of available gain before feedback, speech in quiet, speech in noise (HINT), subjective ratings of hollowness and tolerance, objective measures of the occlusion effect, and real-ear aided response. Results showed less available gain before feedback but less occlusion effect for subjective ratings and objective measures with the reverse horn vent. This type of vent design may be useful to increase the effective vent diameter of custom (including CIC) hearing aids.

Vent configurations on subjective and objective occlusion effect.

The current study reexamined the effect of vent diameters on objective and subjective occlusion effect (OE) while minimizing two possible sources of variability. Nine hearing-impaired participants with primarily a high-frequency hearing loss were evaluated. Laser shell-making technology was used to make ear inserts of completely-in-the-canal (CIC) hearing aids for the study. This was to minimize any potential slit leakage from the inserts. The vent dimensions were systematically altered during the study. Participants sustained /i/ for 5 sec, and the real-ear occluded response was measured with a custom-made program that performed frequency averaging to reduce response variability. Participants also repeated the phrase "Baby Jeannie is teeny tiny" and rated their own voice. The results showed a systematic change in the objective OE and subjective ratings of OE as the vent diameter was modified. Furthermore, a significant correlation was seen between subjective rating and objective occlusion effect.