Effects of Training on the Use of a Manual Microphone Shutoff on a BiCROS Device.

BACKGROUND: Bilateral contralateral routing of signals (BiCROS) hearing aids function to restore audibility of sounds originating from the side of the unaidable ear. However, when speech is presented to the side of the aidable ear and noise to the side of the unaidable ear, a BiCROS arrangement may reduce intelligibility of the speech signal. This negative effect may be circumvented if an on/off switch is available on the contralateral routing of signals (CROS) transmitter. PURPOSE: This study evaluated if the proper use of the on/off switch on a CROS transmitter could enhance speech recognition in noise and sound localization abilities. The participants' subjective reactions to the use of the BiCROS, including the use of the on/off switch in real-life were also evaluated. RESEARCH DESIGN: A between-subjects, repeated-measures design was used to assess differences in speech recognition (in quiet and in noise) and localization abilities under four hearing aid conditions (unaided, unilaterally aided, fixed BiCROS setting, and adjusted BiCROS setting) with speech and noise stimuli presented from different azimuths. Participants were trained on the use of the on/off switch on the BiCROS transmitter before testing in the adjusted BiCROS settings. Subjective ratings were obtained with the Speech, Spatial, and Sound Quality (SSQ) questionnaire and a custom questionnaire. STUDY SAMPLE: Nine adult BiCROS candidates participated in this study. DATA COLLECTION AND ANALYSIS: Participants wore the Widex Dream-m-CB hearing aid on the aidable ear for 1 week. They then wore the BiCROS for the remainder of the study. Speech recognition and localization testing were completed in four hearing aid conditions (unaided, unilateral aided, fixed BiCROS, and adjusted BiCROS). Speech recognition was evaluated during the first three visits, whereas localization was evaluated over the course of the study. Participants completed the SSQ questionnaire before each visit. The CROS questionnaire was completed at the final visit. A repeated measures analysis of variance with Bonferroni post hoc analysis was used to evaluate the significance of the results on speech recognition, localization, and the SSQ. RESULTS: The results revealed that the adjusted BiCROS condition improved speech recognition scores by 20 rau (rationalized arcsine unit) when speech was presented to the aidable ear and localization by 37% when sounds are presented from the side of the unaidable ear over the fixed BiCROS condition. Statistically significant benefit on the SSQ was also noted with the adjusted BiCROS condition compared to the unilateral fitting. CONCLUSIONS: These findings supported the value of an on/off switch on a CROS transmitter because it allows convenient selective transmission of sounds. It also highlighted the importance of instructions and practice in using the BiCROS hearing aid successfully.

Speech intelligibility benefits of hearing AIDS at various input levels.

BACKGROUND: Although the benefits of hearing aids are generally recognized for soft- and conversational-level sounds, most studies have reported negative benefits (i.e., poorer aided than unaided performance) at high noise inputs. Advances in digital signal processing such as compression, noise reduction, and directional microphone could improve speech perception at high input levels. This could alter our view on the efficacy of hearing aids in loud, noisy situations. PURPOSE: The current study compared the aided versus the unaided speech intelligibility performance of hearing-impaired (HI) listeners at various input levels (from 50-100 dB SPL) and signal-to-noise ratios (SNRs; quiet, +6, +3, and -3 dB) in order to document the benefits of modern hearing aids. In addition, subjective preference between aided and unaided sounds (speech and music) at various input levels was also compared. RESEARCH DESIGN: The experiment used a factorial repeated-measures design. STUDY SAMPLE: A total of 10 HI adults with symmetrical moderate to severe hearing losses served as test participants. In addition, speech intelligibility scores of five normal-hearing (NH) listeners were also measured for comparison. INTERVENTION: Speech perception was studied at 50 and 65 dB SPL input levels in quiet and also in noise at levels of 65, 85, and 100 dB SPL with SNRs of +6, +3, and -3 dB. This was done for all participants (HI and NH). In addition, the HI participants compared subjective preference between the aided and unaided presentations of speech and music stimuli at 50, 65, 85, and 100 dB SPL in quiet. DATA COLLECTION AND ANALYSIS: The data were analyzed with repeated-measures analysis of variance. RESULTS: The results showed a decrease in aided benefits as input levels increased. However, even at the two highest input levels (i.e., 85 and 100 dB SPL), aided speech scores were still higher than the unaided speech scores. Furthermore, NH listeners and HI listeners in the aided condition showed stable speech-in-noise performance between 65 and 100 dB SPL input levels, except that the absolute performance of the NH listeners was higher than that of the HI listeners. Subjective preference for the unaided sounds versus the aided sounds increased as input level increased, with a crossover intensity at approximately 75 dB SPL for speech and 80 dB SPL for music. CONCLUSIONS: The results supported the hypothesis that the study hearing aid can provide aided speech-in-noise benefit at very high noise inputs in a controlled environment.

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.

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.