Is It Okay to Use Compressed NU-6 Files for Clinical Word Recognition Testing?

PURPOSE: The purpose of this study was to evaluate the impact of file compression on clinically measured word recognition scores obtained using the Northwestern University Test Number Six (NU-6; Auditec recording) materials. METHOD: Participants were 86 adults (N = 170 ears; M age = 65.5). The 25 most difficult words from each of four NU-6 test lists were used to measure word recognition. Two lists were compressed using a freely available Advanced Audio Coding compression algorithm and two were not. Word recognition was measured in each ear using one compressed file and one uncompressed file. Percent correct scores were calculated in each test condition and log transformed for analyses. Clinically meaningful differences between uncompressed and compressed scores were examined using 95% critical difference ranges. The effects of file compression on word recognition scores were examined in the context of multiple potential confounding effects, including age and degree of hearing loss, using linear mixed-effects models (LMMs). RESULTS: Differences between compressed and uncompressed scores in a given ear exceeded the 95% critical difference range in about 7% of cases, approximating the 5% of expected cases occurring due to chance. Likewise, LMM results revealed no significant effect of file compression on clinically measured NU-6 word recognition scores and no significant interactions between compression effects and age or degree of hearing loss. CONCLUSIONS: While the original uncompressed audio files are clearly the most appropriate stimuli for clinical purposes, our study results suggest that file compression, even at an aggressive 64 kilobits per second, does not have a statistically significant, or clinically meaningful, effect on word recognition scores when measured using these Auditec materials.

Clinical evaluation of a new hearing aid anti-cardioid directivity pattern.

OBJECTIVE: The purpose of this research was to evaluate a new directional hearing aid algorithm which automatically adapts to an anti-cardioid pattern in background noise when a speech signal originates from behind the hearing aid user. DESIGN: Using the hearing-in-noise-test (HINT) in the soundfield, with the sentences delivered adaptively from the back (180°) and the standard HINT competing noise from the front (0°; 72 dB SPL), the participants were tested for three different hearing aid conditions: omnidirectional, conventional adaptive directional, and adaptive directional with the anti-cardioid algorithm enabled. STUDY SAMPLE: Adults (n = 21) with bilaterally symmetrical downward sloping sensorineural hearing loss; experienced hearing aid users and aided bilaterally for experimental testing. RESULTS: Results revealed a significant effect for the hearing aid microphone setting (p < .0001), with a HINT mean RTS of 4.2 dB for conventional adaptive directional, -0.1 dB for omnidirectional, and -5.7 dB when the anti-cardioid algorithm was active. This was a large effect size (Cohen's f2). CONCLUSION: The findings suggest that the signal classification system steered the algorithm correctly, and that when implemented, the anti-cardioid polar pattern resulted in an improvement in speech recognition in background noise for this listening situation.

Statistically derived factors of varied importance to audiologists when making a hearing aid brand preference decision.

PURPOSE: To determine the amount of importance audiologists place on various items related to their selection of a preferred hearing aid brand manufacturer. RESEARCH DESIGN: Three hundred forty-three hearing aid-dispensing audiologists rated a total of 32 randomized items by survey methodology. RESULTS: Principle component analysis identified seven orthogonal statistical factors of importance. In rank order, these factors were Aptitude of the Brand, Image, Cost, Sales and Speed of Delivery, Exposure, Colleague Recommendations, and Contracts and Incentives. While it was hypothesized that differences among audiologists in the importance ratings of these factors would dictate their preference for a given brand, that was not our finding. Specifically, mean ratings for the six most important factors did not differ among audiologists preferring different brands. A statistically significant difference among audiologists preferring different brands was present, however, for one factor: Contracts and Incentives. Its assigned importance, though, was always lower than that for the other six factors. CONCLUSIONS: Although most audiologists have a preferred hearing aid brand, differences in the perceived importance of common factors attributed to brands do not largely determine preference for a particular brand.

User preference and reliability of bilateral hearing aid gain adjustments.

The purpose of the current study was to evaluate the consistency and reliability of user adjustments to hearing aid gain and the resulting effects on speech understanding. Sixteen bilaterally aided individuals with hearing loss adjusted their hearing aid gain to optimize listening comfort and speech clarity while listening to speech in quiet and noisy backgrounds. Following these adjustments, participants readjusted their aids to optimize clarity and comfort while listening to speech in quiet. These final gain settings were recorded and compared to those provided by NAL-NL1 prescriptive targets. In addition, speech understanding was tested with the hearing aids set at target and user gain settings. Performance differences between the gain settings were then assessed. Study results revealed that although some listeners preferred more or less gain than prescribed, on average, user and prescribed gain settings were similar in both ears. Some individuals, however, made gain adjustments between ears resulting in "gain mismatches." These "mismatches" were often inconsistent across trials suggesting that these adjustments were unreliable. Speech testing results, however, showed no significant difference across the different gain settings suggesting that the gain deviations introduced in this study were not large enough to significantly affect speech understanding.

Using trainable hearing aids to examine real-world preferred gain.

BACKGROUND: While there have been many studies of real-world preferred hearing aid gain, few data are available from participants using hearing aids with today's special features activated. Moreover, only limited data have been collected regarding preferred gain for individuals using trainable hearing aids. PURPOSE: To determine whether real-world preferred hearing aid gain with trainable modern hearing aids is in agreement with previous work in this area, and to determine whether the starting programmed gain setting influences preferred gain outcome. RESEARCH DESIGN: An experimental crossover study. Participants were randomly assigned to one of two treatment groups. Following initial treatment, each subject crossed to the opposite group and experienced that treatment. STUDY SAMPLE: Twenty-two adults with downward sloping sensorineural hearing loss served as participants (mean age 64.5; 16 males, 6 females). All were experienced users of bilateral amplification. INTERVENTION: Using a crossover design, participants were fitted to two different prescriptive gain conditions: VC (volume control) start-up 6 dB above NAL-NL1 (National Acoustic Laboratories-Non-linear 1) target or VC start-up 6 dB below NAL-NL1 target. The hearing aids were used in a 10 to 14 day field trial for each condition, and using the VC, the participants could "train" the overall hearing aid gain to their preferred level. During the field trial, daily hearing aid use was logged, as well as the listening situations experienced by the listeners based on the hearing instrument's acoustic scene analysis. The participants completed a questionnaire at the start and end of each field trial in which they rated loudness perceptions and their satisfaction with aided loudness levels. RESULTS: Because several participants potentially experienced floor or ceiling effects for the range of trainable gain, the majority of the statistical analysis was conducted using 12 of the 22 participants. For both VC-start conditions, the trained preferred gain differed significantly from the NAL-NL1 prescriptive targets. More importantly, the initial start-up gain significantly influenced the trained gain; the mean preferred gain for the +6 dB start condition was approximately 9 dB higher than the preferred gain for the -6 dB start condition, and this difference was statistically significant (p < .001). Partial eta squared (n2) = 0.919, which is a large effect size. Deviation from the NAL-NL1 target was not significantly influenced by the time spent in different listening environments, amount of hearing aid use during the trial period, or amount of hearing loss. Questionnaire data showed more appropriate ratings for loudness and higher satisfaction with loudness for the 6 dB below target VC-start condition. CONCLUSIONS: When trainable hearing aids are used, the initial programmed gain of hearing instruments can influence preferred gain in the real world.

The effects of digital noise reduction on the acceptance of background noise.

Modern hearing aids commonly employ digital noise reduction (DNR) algorithms. The potential benefit of these algorithms is to provide improved speech understanding in noise or, at the least, to provide relaxed listening or increased ease of listening. In this study, 22 adults were fitted with 16-channel wide-dynamic-range compression hearing aids containing DNR processing. The DNR includes both modulation-based and Wiener-filter-type algorithms working simultaneously. Both speech intelligibility and acceptable noise level (ANL) were assessed using the Hearing in Noise Test (HINT) with DNR on and DNR off. The ANL was also assessed without hearing aids. The results showed a significant mean improvement for the ANL (4.2 dB) for the DNR-on condition when compared to DNR-off condition. Moreover, there was a significant correlation between the magnitude of ANL improvement (relative to DNR on) and the DNR-off ANL. There was no significant mean improvement for the HINT for the DNR on condition, and on an individual basis, the HINT score did not significantly correlate with either aided ANL (DNR on or DNR off). These findings suggest that at least within the constraints of the DNR algorithms and test conditions employed in this study, DNR can significantly improve the clinically measured ANL, which may result in improved ease of listening for speech-in-noise situations.

Amplification with digital noise reduction and the perception of annoying and aversive sounds.

Hearing aid users report difficulties using their hearing aids in noisy environments. Problems include understanding speech, loudness discomfort, and annoyance with background noise. Digital noise reduction algorithms have been promoted as a method to solve speech understanding and comfort in noise problems. Research has failed to find improved speech understanding in noise. Little is known about how digital noise reduction affects noise annoyance and aversiveness. The goals of this investigation were to determine how a specific digital noise reduction system affects hearing aid users' perception of noise annoyance and aversiveness and to compare their perceptions to those of normal-hearing listeners. Ratings of noise annoyance and of aversiveness were obtained from 49 participants with moderate sensorineural hearing loss before fitting and after 3 weeks of hearing aid use. Findings were compared to measures obtained from normal-hearing listeners. Perceived annoyance and aversiveness increased with amplification. Annoyance and aversiveness with the hearing aid approximated normal perception. The results of this investigation suggest the need for counseling patients about realistic expectations related to annoyance and aversiveness of sounds at the time of hearing aid fitting.

Evaluation of a second-order directional microphone hearing aid: I. Speech perception outcomes.

This clinical trial was undertaken to evaluate the benefit obtained from hearing aids employing second-order adaptive directional microphone technology, used in conjunction with digital noise reduction. Data were collected for 49 subjects across two sites. New and experienced hearing aid users were fit bilaterally with behind-the-ear hearing aids using the National Acoustics Laboratory-Nonlinear version 1 (NAL-NL1) prescriptive method with manufacturer default settings for various parameters of signal processing (e.g., noise reduction, compression, etc.). Laboratory results indicated that (1) for the stationary noise environment, directional microphones provided better speech perception than omnidirectional microphones, regardless of the number of microphones; and (2) for the moving noise environment, the three-microphone option (whether in adaptive or fixed mode) and the two-microphone option in its adaptive mode resulted in better performance than the two-microphone fixed mode, or the omnidirectional modes.

Evaluation of a second-order directional microphone hearing aid: II. Self-report outcomes.

This clinical trial was undertaken to evaluate the subjective benefit obtained from hearing aids employing automatic switching second-order adaptive directional microphone technology, used in conjunction with digital noise reduction, as compared to a fixed directional microphone or omnidirectional microphone response with the same digital noise reduction. Data were collected for 49 participants across two sites. Both new and experienced hearing aid users were fit bilaterally with behind-the-ear hearing aids using the NAL-NL1 (National Acoustics Laboratory-Nonlinear version 1) prescriptive method with manufacturer default settings for various signal processing (e.g., noise reduction, compression parameters, etc.). During ten days of hearing aid use, participants responded to daily journal questions. Subjective ratings for each of the three hearing aid responses (omnidirectional, automatic-adaptive directional, and automatic-fixed directional) were similar. Overall preference for a microphone condition was equally distributed between no preference, omnidirectional, and automatic adaptive and/or fixed directional.

Fitting hearing aids to adults using prescriptive methods: an evidence-based review of effectiveness.

The use of a prescriptive fitting approach for hearing aid selection has been a common practice for the past 60-70 years. While there are prescriptive approaches that have been validated, in recent years it has become popular to deviate from these validated methods and use manufacturers' proprietary algorithms, which in many cases are significantly different. This research review was designed to examine if there was evidence supporting the use of specific gain requirements for hearing aid fitting. Specifically, the question that was asked was "Are there real-world outcome measures from adult patients that show a preference for the gain prescribed by a specific prescriptive fitting procedure?" Inclusion criteria were as follows: adult subjects, consistent technology (e.g., different prescriptive methods compared using same hearing aids), real-ear verification of gain, and real-world outcome measures. For this review, in addition to subjective responses, preferred use gain was considered a real-world outcome measure. The National Acoustic Laboratories' revised (NAL-R), revised for severe/profound (NAL-RP), and the National Acoustic Laboratories-Non-Linear 1 (NAL-NL1) prescriptive methods were used as a common reference, as they have been the most commonly studied methods with adults. Eleven studies were identified that met the inclusion criteria. Eight of the studies supported gain similar to that prescribed by the NAL-R or NAL-RP methods; three studies supported prescribed gain less than the NAL-R or NAL-RP. There was no evidence that gain greater than that prescribed by the NAL methods should be used. The level of evidence was moderate, as the supporting studies were either Level 2 or Level 4, and the statistical power of the studies was low.

Fitting hearing aids using clinical measures of loudness discomfort levels: an evidence-based review of effectiveness.

Clinical measurement of the loudness discomfort level (LDL) historically has been part of the hearing aid fitting procedure, and this clinical practice remains popular today. LDL measurements also are recommended in contemporary hearing aid fitting protocols. Yet, surveys show that many hearing aid users are dissatisfied with the loudness of their hearing aids. In this evidence-based review article, we evaluate the effectiveness of clinical LDL measurements. Specifically, we asked the question "Are the clinical measurements of LDL for adult patients predictive of aided acceptance and satisfaction of loudness for high inputs in the real world?" Nearly 200 articles were reviewed; three met the criteria set forth in this review. The evidence supported using unaided LDLs for selecting the maximum real-ear output of hearing aids. No study using aided LDLs or aided loudness verification met the criteria. The level of the evidence for the three articles using unaided LDLs was low; no higher than Level 4. The limited number of studies, the level of evidence, and the statistical power of the studies prevents us from making a strong recommendation concerning the clinical use of LDL measures. Additional research in this area, especially research employing randomized controlled trials would be a useful addition to this body of literature.