Sentence Recognition in Steady-State Speech-Shaped Noise versus Four-Talker Babble

2019 ◽  
Vol 30 (01) ◽  
pp. 054-065
Author(s):  
Andrew J. Vermiglio ◽  
Caroline C. Herring ◽  
Paige Heeke ◽  
Courtney E. Post ◽  
Xiangming Fang

AbstractSpeech recognition in noise (SRN) evaluations reveal information about listening ability that is unavailable from pure-tone thresholds. Unfortunately, SRN evaluations are not commonly used in the clinic. A lack of standardization may be an explanation for the lack of widespread acceptance of SRN testing. Arguments have been made for the utilization of steady-state speech-shaped noise vs. multi-talker babble. Previous investigations into the effect of masker type have used a monaural presentation of the stimuli. However, results of monaural SRN tests cannot be generalized to binaural listening conditions.The purpose of this study was to investigate the effect of masker type on SRN thresholds under binaural listening conditions.The Hearing in Noise Test (HINT) protocol was selected in order to measure SRN thresholds in steady-state speech-shaped noise (HINT noise) and four-talker babble with and without the spatial separation of the target speech and masker stimuli.Fifty native speakers of English with normal pure-tone thresholds (≤ 25 dB HL, 250–4000 Hz) participated in the study. The mean age was 20.5 years (SD 1.01).All participants were tested using the standard protocol for the HINT in a simulated soundfield environment under TDH-50P headphones. Thresholds were measured for the Noise Front, Noise Left, and Noise Right listening conditions with HINT noise and four-talker babble. The HINT composite score was determined for each noise condition. The spatial advantage was calculated from the HINT thresholds. Pure-tone threshold data were collected using the modified Hughson-Westlake procedure. Statistical analyses include descriptive statistics, effect size, correlations, and repeated measures ANOVA followed by matched-pairs t-tests.Repeated measures ANOVA was conducted to investigate the effects of masker type and noise location on HINT thresholds. Both main effects and their interaction were statistically significant (p < 0.01). No significant differences were found between masker conditions for the Noise Front thresholds. However, for the Noise Side conditions the four-talker babble thresholds were significantly better than the HINT noise thresholds. Overall, greater spatial advantage was found for the four-talker babble as opposed to the HINT noise conditions (p < 0.01). Pearson correlation analysis revealed no significant relationships between four-talker babble and HINT noise speech recognition performances for the Noise Front, Noise Right conditions, and the spatial advantage measures. Significant relationships (p < 0.05) were found between masking noise performances for the Noise Left condition and the Noise Composite scores.One cannot assume that a patient who performs within normal limits on a speech in four-talker babble test will also perform within normal limits on a speech in steady-state speech-shaped noise test, and vice-versa. Additionally, performances for the Noise Front condition cannot be used to predict performances for the Noise Side conditions. The utilization of both HINT noise and four-talker babble maskers, with and without the spatial separation of the stimuli, may be useful when determining the range of speech recognition in noise abilities found in everyday listening conditions.

Author(s):  
Andrew J. Vermiglio ◽  
Lauren Leclerc ◽  
Meagan Thornton ◽  
Hannah Osborne ◽  
Elizabeth Bonilla ◽  
...  

Purpose The goal of this study was to determine the ability of the AzBio speech recognition in noise (SRN) test to distinguish between groups of participants with and without a self-reported SRN disorder and a self-reported signal-to-noise ratio (SNR) loss. Method Fifty-four native English-speaking young adults with normal pure-tone thresholds (≤ 25 dB HL, 0.25–6.0 kHz) participated. Individuals who reported hearing difficulty in a noisy restaurant (Reference Standard 1) were placed in the SRN disorder group. SNR loss groups were created based on the self-report of the ability to hear Hearing in Noise Test (HINT) sentences in steady-state speech-shaped noise, four-talker babble, and 20-talker babble in a controlled listening environment (Reference Standard 2). Participants with HINT thresholds poorer than or equal to the median were assigned to the SNR loss group. Results The area under the curve from the receiver operating characteristics curves revealed that the AzBio test was not a significant predictor of an SRN disorder, or an SNR loss using the steady-state noise Reference Standard 2 condition. However, the AzBio was a significant predictor of an SNR loss using the four-talker babble and 20-talker babble Reference Standard 2 conditions ( p < .05). The AzBio was a significant predictor of an SNR loss when using the average HINT thresholds across the three Reference Standard 2 masker conditions (area under the curve = .79, p = .001). Conclusions The AzBio test was not a significant predictor of a self-reported SRN disorder or a self-reported SNR loss in steady-state noise. However, it was a significant predictor of a self-reported SNR loss in babble noise and the average across all noise conditions. A battery of reference standard tests with a range of maskers in a controlled listening environment is recommended for diagnostic accuracy evaluations of SRN tests.


2008 ◽  
Vol 19 (07) ◽  
pp. 548-556 ◽  
Author(s):  
Richard H. Wilson ◽  
Wendy B. Cates

Background: The Speech Recognition in Noise Test (SPRINT) is a word-recognition instrument that presents the 200 Northwestern University Auditory Test No. 6 (NU-6) words binaurally at 50 dB HL in a multitalker babble at a 9 dB signal-to-noise ratio (S/N) (Cord et al, 1992). The SPRINT was developed by and used by the Army as a more valid predictor of communication abilities (than pure-tone thresholds or word-recognition in quiet) for issues involving fitness for duty from a hearing perspective of Army personnel. The Words-in-Noise test (WIN) is a slightly different word-recognition task in a fixed level multitalker babble with 10 NU-6 words presented at each of 7 S/N from 24 to 0 dB S/N in 4 dB decrements (Wilson, 2003; Wilson and McArdle, 2007). For the two instruments, both the babble and the speakers of the words are different. The SPRINT uses all 200 NU-6 words, whereas the WIN uses a maximum of 70 words. Purpose: The purpose was to compare recognition performances by 24 young listeners with normal hearing and 48 older listeners with sensorineural hearing on the SPRINT and WIN protocols. Research Design: A quasi-experimental, mixed model design was used. Study Sample: The 24 young listeners with normal hearing (19 to 29 years, mean = 23.3 years) were from the local university and had normal hearing (≤20 dB HL; American National Standards Institute, 2004) at the 250–8000 Hz octave intervals. The 48 older listeners with sensorineural hearing loss (60 to 82 years, mean = 69.9 years) had the following inclusion criteria: (1) a threshold at 500 Hz between 15 and 30 dB HL, (2) a threshold at 1000 Hz between 20 and 40 dB HL, (3) a three-frequency pure-tone average (500, 1000, and 2000 Hz) of ≤40 dB HL, (4) word-recognition scores in quiet ≥40%, and (5) no history of middle ear or retrocochlear pathology as determined by an audiologic evaluation. Data Collection and Analysis: The speech materials were presented bilaterally in the following order: (1) the SPRINT at 50 dB HL, (2) two half lists of NU-6 words in quiet at 60 dB HL and 80 dB HL, and (3) the two 35-word lists of the WIN materials with the multitalker babble fixed at 60 dB HL. Data collection occurred during a 40–60 minute session. Recognition performances on each stimulus word were analyzed. Results: The listeners with normal hearing obtained 92.5% correct on the SPRINT with a 50% point on the WIN of 2.7 dB S/N. The listeners with hearing loss obtained 65.3% correct on the SPRINT and a WIN 50% point at 12.0 dB S/N. The SPRINT and WIN were significantly correlated (r = −0.81, p < .01), indicating that the SPRINT had good concurrent validity. The high-frequency, pure-tone average (1000, 2000, 4000 Hz) had higher correlations with the SPRINT, WIN, and NU-6 in quiet than did the traditional three-frequency pure-tone average (500, 1000, 2000 Hz). Conclusions: Graphically and numerically the SPRINT and WIN were highly related, which is indicative of good concurrent validity of the SPRINT.


2009 ◽  
Vol 20 (04) ◽  
pp. 264-271 ◽  
Author(s):  
Karen S. Helfer ◽  
Megan Vargo

Purpose: This study was designed to examine speech understanding ability and temporal processing in middle-aged women with normal or near-normal pure-tone thresholds. Research Design: Speech understanding, temporal processing ability, and self-assessed hearing were measured in groups of younger and middle-aged females. Study Sample: Participants were younger and middle-aged females (n = 12 per group) with normal hearing through 4000 Hz bilaterally. Subjects were drawn from nonclinical populations. Data Collection and Analysis: Speech understanding was measured in the presence of steady-state noise and competing speech, with and without perceived spatial separation of the target speech and masker. The Gaps-In-Noise (GIN) test (Musiek et al, 2005) was used to assess temporal resolution ability. In addition, subjects completed a questionnaire with several items from the Speech, Spatial, and Qualities of Hearing Scale (Gatehouse and Noble, 2004) to gauge their subjective ability to understand speech in complex listening situations. Data were analyzed via repeated-measures ANOVA and Pearson r correlations. Results: Results showed that the performance of the middle-aged subjects was significantly poorer than that of the younger participants in the presence of a spatially coincident speech masker. Although performance in this listening condition was unrelated to pure-tone thresholds, it was strongly correlated with scores on the GIN test. Speech understanding performance in the presence of a steady-state masker was related to high-frequency pure-tone thresholds. Conclusions: These results suggest that some middle-aged women with little or no pure-tone hearing loss experience listening difficulty in complex environments. Results also suggest a strong relationship between temporal processing and speech understanding in certain competing speech situations.


2019 ◽  
Vol 30 (05) ◽  
pp. 431-443 ◽  
Author(s):  
Erin C. Schafer ◽  
Kamakshi V. Gopal ◽  
Lauren Mathews ◽  
Skyler Thompson ◽  
Kara Kaiser ◽  
...  

AbstractIndividuals who have a normal pure-tone audiogram but are diagnosed with autism spectrum disorder (ASD) often exhibit poorer speech recognition and auditory processing when compared with neurotypical peers with normal pure-tone audiograms.The purpose of this study was to determine the efficacy and effectiveness of a 12-week auditory processing training (APT) program that was designed to address the deleterious effects of background noise and auditory processing deficits that are common among individuals diagnosed with ASD.A repeated measures design was used.The sample consisted of 15 high-functioning children and young adults who had a formal diagnosis of ASD and who were recruited from local clinics and school districts.Participants completed the 12-week APT program consisting of computerized dichotic training, one-on-one therapist-directed auditory training, and the use of remote microphone (RM) technology at home and in the classroom.Participants completed a comprehensive test battery to assess general auditory processing skills, speech recognition in noise, acceptance of background noise, spatial processing, binaural integration abilities, self-perceived difficulties, and observed behaviors. Testing was conducted before (n = 15), immediately after (n = 15), and 12 weeks after (n = 7) the completion of the APT program. Paired t-tests, repeated measures analysis of variance, or nonparametric tests were used to analyze the data.On average, the APT program significantly enhanced general auditory processing abilities, including binaural integration and subjective listening abilities in the classroom. When the RM was used, significantly improved speech recognition and improved acceptance of background noise was measured relative to a condition with no technology.Following the APT program, the participants exhibited the greatest improvements in testing that required binaural integration and auditory working memory. The use of the RM technology was able to address the deleterious effects of noise on speech recognition in noise and acceptance of noise levels.


2020 ◽  
Vol 50 (1) ◽  
pp. 9
Author(s):  
Widayat Alviandi ◽  
Jenny Bashiruddin ◽  
Brastho Bramantyo ◽  
Farisa Rizky

Background: Patients with hearing disturbance will generally undergo pure tone audiometry andspeech audiometry in a quiet room, but those examinations cannot evaluate the ability to understand speech in daily environment with a noisy background. Words in noise test will provide valuable informationregarding patient’s hearing problem in noise. Purpose: To evaluate the hearing threshold using wordsin noise test in adults with normal hearing. Method: This cross-sectional study was conducted in CiptoMangunkusumo Hospital from January to April 2017. All subjects who fulfilled the inclusion and exclusioncriteria underwent pure tone audiometry, speech audiometry, and words in noise test. Results: A total of71 individuals with normal hearing were recruited for this study. Words in noise test showed the medianvalue of 67 dB and 100 dB for Speech Recognition Threshold (SRT) 50% and Speech DiscriminationScore (SDS) 100%, respectively. The SRT 50% and SDS 100% were significantly higher in the age group40–60 years compared to the age group 18–39 years. There was also a statistically significant differencebetween males and females at SRT 50% assessed by words in noise audiometry. Conclusion: Wordsin noise test showed a statistically significant difference in SRT 50% and SDS 100% between two agegroups, but no difference was found between genders. The result of this study can be used as a referencefor SRT and SDS values of speech audiometry test in noise.Keywords: words in noise, speech audiometry, speech recognition threshold, speech discrimination score ABSTRAKLatar belakang: Pasien dengan gangguan pendengaran umumnya menjalani pemeriksaanaudiometri nada murni dan audiometri tutur di ruangan yang sunyi, tetapi pemeriksaan ini tidakdapat menggambarkan kemampuan pemahaman wicara di lingkungan sehari-hari yang ramai. Testutur dalam bising dapat mengevaluasi masalah pendengaran pasien dalam keadaan bising. Tujuan:Untuk mengevaluasi ambang pendengaran menggunakan tes tutur dalam bising pada orang dewasadengan pendengaran normal. Metode: Penelitian potong lintang ini dilakukan di Rumah Sakit CiptoMangunkusumo dari Januari hingga April 2017. Semua subjek yang memenuhi kriteria inklusi daneksklusi menjalani pemeriksaan audiometri nada murni, audiometri tutur, dan tes tutur dalam bising.Hasil: Sebanyak 71 orang dengan pendengaran normal diikutsertakan dalam penelitian ini. Tes tuturdalam bising menunjukkan nilai median masing-masing 67 dB dan 100 dB pada Speech RecognitionThreshold (SRT) 50% dan Speech Discrimination Score (SDS) 100%. SRT 50% dan SDS 100% secarasignifikan lebih tinggi pada kelompok usia 40–60 tahun dibandingkan dengan kelompok usia 18–39 tahun. Hasil pemeriksaan tes tutur dalam bising menunjukkan perbedaan yang signifikan antara laki-laki dan wanita pada nilai SRT 50%. Kesimpulan: Tes tutur dalam bising menunjukkan perbedaan yang bermakna secara statistik pada SRT 50% dan SDS 100% antara dua kelompok umur, tetapi tidak ada perbedaan signifikan diantara jenis kelamin. Hasil penelitian ini dapat digunakan sebagai acuan untuk nilai SRT dan SDS pada pemeriksaan audiometri tutur dalam bising.


2012 ◽  
Vol 23 (03) ◽  
pp. 171-181 ◽  
Author(s):  
Rachel A. McArdle ◽  
Mead Killion ◽  
Monica A. Mennite ◽  
Theresa H. Chisolm

Background: The decision to fit one or two hearing aids in individuals with binaural hearing loss has been debated for years. Although some 78% of U.S. hearing aid fittings are binaural (Kochkin , 2010), Walden and Walden (2005) presented data showing that 82% (23 of 28 patients) of their sample obtained significantly better speech recognition in noise scores when wearing one hearing aid as opposed to two. Purpose: To conduct two new experiments to fuel the monaural/binaural debate. The first experiment was a replication of Walden and Walden (2005), whereas the second experiment examined the use of binaural cues to improve speech recognition in noise. Research Design: A repeated measures experimental design. Study Sample: Twenty veterans (aged 59–85 yr), with mild to moderately severe binaurally symmetrical hearing loss who wore binaural hearing aids were recruited from the Audiology Department at the Bay Pines VA Healthcare System. Data Collection and Analysis: Experiment 1 followed the procedures of the Walden and Walden study, where signal-to-noise ratio (SNR) loss was measured using the Quick Speech-in-Noise (QuickSIN) test on participants who were aided with their current hearing aids. Signal and noise were presented in the sound booth at 0° azimuth under five test conditions: (1) right ear aided, (2) left ear aided, (3) both ears aided, (4) right ear aided, left ear plugged, and (5) unaided. The opposite ear in (1) and (2) was left open. In Experiment 2, binaural Knowles Electronics Manikin for Acoustic Research (KEMAR) manikin recordings made in Lou Malnati's pizza restaurant during a busy period provided a typical real-world noise, while prerecorded target sentences were presented through a small loudspeaker located in front of the KEMAR manikin. Subjects listened to the resulting binaural recordings through insert earphones under the following four conditions: (1) binaural, (2) diotic, (3) monaural left, and (4) monaural right. Results: Results of repeated measures ANOVAs demonstrated that the best speech recognition in noise performance was obtained by most participants with both ears aided in Experiment 1 and in the binaural condition in Experiment 2. Conclusions: In both experiments, only 20% of our subjects did better in noise with a single ear, roughly similar to the earlier Jerger et al (1993) finding that 8–10% of elderly hearing aid users preferred one hearing aid.


2009 ◽  
Vol 20 (07) ◽  
pp. 409-421 ◽  
Author(s):  
Jace Wolfe ◽  
Erin C. Schafer ◽  
Benjamin Heldner ◽  
Hans Mülder ◽  
Emily Ward ◽  
...  

Background: Use of personal frequency-modulated (FM) systems significantly improves speech recognition in noise for users of cochlear implants (CIs). Previous studies have shown that the most appropriate gain setting on the FM receiver may vary based on the listening situation and the manufacturer of the CI system. Unlike traditional FM systems with fixed-gain settings, Dynamic FM automatically varies the gain of the FM receiver with changes in the ambient noise level. There are no published reports describing the benefits of Dynamic FM use for CI recipients or how Dynamic FM performance varies as a function of CI manufacturer. Purpose: To evaluate speech recognition of Advanced Bionics Corporation or Cochlear Corporation CI recipients using Dynamic FM vs. a traditional FM system and to examine the effects of Autosensitivity on the FM performance of Cochlear Corporation recipients. Research Design: A two-group repeated-measures design. Participants were assigned to a group according to their type of CI. Study Sample: Twenty-five subjects, ranging in age from 8 to 82 years, met the inclusion criteria for one or more of the experiments. Thirteen subjects used Advanced Bionics Corporation, and 12 used Cochlear Corporation implants. Intervention: Speech recognition was assessed while subjects used traditional, fixed-gain FM systems and Dynamic FM systems. Data Collection and Analysis: In Experiments 1 and 2, speech recognition was evaluated with a traditional, fixed-gain FM system and a Dynamic FM system using the Hearing in Noise Test sentences in quiet and in classroom noise. A repeated-measures analysis of variance (ANOVA) was used to evaluate effects of CI manufacturer (Advanced Bionics and Cochlear Corporation), type of FM system (traditional and dynamic), noise level, and use of Autosensitivity for users of Cochlear Corporation implants. Experiment 3 determined the effects of Autosensitivity on speech recognition of Cochlear Corporation implant recipients when listening through the speech processor microphone with the FM system muted. A repeated-measures ANOVA was used to examine the effects of signal-to-noise ratio and Autosensitivity. Results: In Experiment 1, use of Dynamic FM resulted in better speech recognition in noise for Advanced Bionics recipients relative to traditional FM at noise levels of 65, 70, and 75 dB SPL. Advanced Bionics recipients obtained better speech recognition in noise with FM use when compared to Cochlear Corporation recipients. When Autosensitivity was enabled in Experiment 2, the performance of Cochlear Corporation recipients was equivalent to that of Advanced Bionics recipients, and Dynamic FM was significantly better than traditional FM. Results of Experiment 3 indicate that use of Autosensitivity improves speech recognition in noise of signals directed to the speech processor relative to no Autosensitivity. Conclusions: Dynamic FM should be considered for use with persons with CIs to improve speech recognition in noise. At default CI settings, FM performance is better for Advanced Bionics recipients when compared to Cochlear Corporation recipients, but use of Autosensitivity by Cochlear Corporation users results in equivalent group performance.


2018 ◽  
Vol 29 (10) ◽  
pp. 948-954 ◽  
Author(s):  
Paige Heeke ◽  
Andrew J. Vermiglio ◽  
Emery Bulla ◽  
Keerthana Velappan ◽  
Xiangming Fang

AbstractTemporal acoustic cues are particularly important for speech understanding, and past research has inferred a relationship between temporal resolution and speech recognition in noise ability. A temporal resolution disorder is thought to affect speech understanding abilities because persons would not be able to accurately encode these frequency transitions, creating speech discrimination errors even in the presence of normal pure-tone hearing.The primary purpose was to investigate the relationship between temporal resolution as measured by the Random Gap Detection Test (RGDT) and speech recognition in noise performance as measured by the Hearing in Noise Test (HINT) in adults with normal audiometric thresholds. The second purpose was to examine the relationship between temporal resolution and spatial release from masking.The HINT and RGDT protocols were administered under headphones according to the guidelines specified by the developers. The HINT uses an adaptive protocol to determine the signal-to-noise ratio where the participant recognizes 50% of the sentences. For HINT conditions, the target sentences were presented at 0° and the steady-state speech-shaped noise and a four-talker babble (4TB) was presented at 0°, +90°, or −90° for noise front, noise right, and noise left conditions, respectively. The RGDT is used to evaluate temporal resolution by determining the smallest time interval between two matching stimuli that can be detected by the participant. The RGDT threshold is the shortest time interval where the participant detects a gap. Tonal (0.5, 1, 2, and 4 kHz) and click stimuli random gap subtests were presented at 60 dB HL. Tonal subtests were presented in a random order to minimize presentation order effects.Twenty-one young, native English-speaking participants with normal pure-tone thresholds (≤25 dB HL for 500–4000 Hz) participated in this study. The average age of the participants was 20.2 years (SD = 0.66).Spearman rho correlation coefficients were conducted using SPSS 22 (IBM Corp., Armonk, NY) to determine the relationships between HINT and RGDT thresholds and derived measures (spatial advantage and composite scores). Nonparametric testing was used because of the ordinal nature of RGDT data.Moderate negative correlations (p < 0.05) were found between eight RGDT and HINT threshold measures and a moderate positive correlation (p < 0.05) was found between RGDT click thresholds and HINT 4TB spatial advantage. This suggests that as temporal resolution abilities worsened, speech recognition in noise performance improved. These correlations were not statistically significant after the p value reflected the Bonferroni correction for multiple comparisons.The results of the present study imply that the RGDT and HINT use different temporal processes. Performance on the RGDT cannot be predicted from HINT thresholds or vice versa.


2011 ◽  
Vol 22 (06) ◽  
pp. 313-331 ◽  
Author(s):  
Véronique Vaillancourt ◽  
Chantal Laroche ◽  
Christian Giguère ◽  
Marc-André Beaulieu ◽  
Jean-Pierre Legault

Background: Auditory fitness for duty (AFFD) testing is an important element in an assessment of workers’ ability to perform job tasks safely and effectively. Functional hearing is particularly critical to job performance in law enforcement. Most often, assessment is based on pure-tone detection thresholds; however, its validity can be questioned and challenged in court. In an attempt to move beyond the pure-tone audiogram, some organizations like the Royal Canadian Mounted Police (RCMP) are incorporating additional testing to supplement audiometric data in their AFFD protocols, such as measurements of speech recognition in quiet and/or in noise, and sound localization. Purpose: This article reports on the assessment of RCMP officers wearing hearing aids in speech recognition and sound localization tasks. The purpose was to quantify individual performance in different domains of hearing identified as necessary components of fitness for duty, and to document the type of hearing aids prescribed in the field and their benefit for functional hearing. The data are to help RCMP in making more informed decisions regarding AFFD in officers wearing hearing aids. Research Design: The proposed new AFFD protocol included unaided and aided measures of speech recognition in quiet and in noise using the Hearing in Noise Test (HINT) and sound localization in the left/right (L/R) and front/back (F/B) horizontal planes. Sixty-four officers were identified and selected by the RCMP to take part in this study on the basis of hearing thresholds exceeding current audiometrically based criteria. This article reports the results of 57 officers wearing hearing aids. Results: Based on individual results, 49% of officers were reclassified from nonoperational status to operational with limitations on fine hearing duties, given their unaided and/or aided performance. Group data revealed that hearing aids (1) improved speech recognition thresholds on the HINT, the effects being most prominent in Quiet and in conditions of spatial separation between target and noise (Noise Right and Noise Left) and least considerable in Noise Front; (2) neither significantly improved nor impeded L/R localization; and (3) substantially increased F/B errors in localization in a number of cases. Additional analyses also pointed to the poor ability of threshold data to predict functional abilities for speech in noise (r2 = 0.26 to 0.33) and sound localization (r2 = 0.03 to 0.28). Only speech in quiet (r2 = 0.68 to 0.85) is predicted adequately from threshold data. Conclusions: Combined with previous findings, results indicate that the use of hearing aids can considerably affect F/B localization abilities in a number of individuals. Moreover, speech understanding in noise and sound localization abilities were poorly predicted from pure-tone thresholds, demonstrating the need to specifically test these abilities, both unaided and aided, when assessing AFFD. Finally, further work is needed to develop empirically based hearing criteria for the RCMP and identify best practices in hearing aid fittings for optimal functional hearing abilities.


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