Hearing Aid Prescription Research Articles

Reference Data for a Quick Speech-in-Noise Hearing Test in the French Language

Introduction: Difficulty in understanding speech in noise is the most common complaint of people with hearing impairment. Thus, there is a need for tests of speech-in-noise ability in clinical settings, which have to be evaluated for each language. Here, a reference dataset is presented for a quick speech-in-noise test in the French language (Vocale Rapide dans le Bruit, VRB; Leclercq, Renard, & Vincent, 2018). Methods: A large cohort (N = 641) was tested in a nationwide multicentric study. The cohort comprised normal-hearing individuals and individuals with a broad range of symmetrical hearing losses. Short everyday sentences embedded in babble noise were presented over a spatial array of loudspeakers. Speech level was kept constant, while noise level was progressively increased over a range of signal-to-noise ratios. The signal-to-noise ratio for which 50% of keywords could be correctly reported (speech reception threshold, SRT) was derived from psychometric functions. Other audiometric measures were collected for the cohort, such as audiograms and speech-in-quiet performance. Results: The VRB test was both sensitive and reliable, as shown by the steep slope of the psychometric functions and by the high test-retest consistency across sentence lists. Correlation analyses showed that pure tone averages derived from the audiograms explained 74% of the SRT variance over the whole cohort, but only 29% for individuals with clinically normal audiograms. SRTs were then compared to recent guidelines from the French Society of Audiology [Eur Ann Otorhinolaryngol Head Neck Dis. 2022;139(1):21–7]. Among individuals who would not have qualified for hearing aid prescription based on their audiogram or speech intelligibility in quiet, 18.4% were now eligible as they displayed SRTs in noise impaired by 3 dB or more. For individuals with borderline audiograms, between 20 dB HL and 30 dB HL, the prevalence of impaired SRTs increased to 71.4%. Finally, even though five lists are recommended for clinical use, a minute-long screening using only one VRB list detected 98.6% of impaired SRTs. Conclusion: The reference data suggest that VRB testing can be used to identify individuals with speech-in-noise impairment.

Comparing LTASS across languages using natural and AI speech samples

Hearing aid prescription protocols rely on estimates of speech spectra. One such estimate, the International Long-Term Average Speech Spectrum (ILTASS), is a common reference for the distribution of spectral energy within speech signals. However, recent research has suggested differences in speech spectra between some languages and the ILTASS standard. These disparities raise questions regarding the applicability of a language-general approach to hearing aid gain application. This study presents a comparative analysis of Long-Term Average Speech Spectra (LTASS) across various languages. Utilizing speech samples from both human and AI sources, LTASS was measured for speakers of different languages. Subsequently, these LTASS profiles were contrasted with the established ILTASS reference. Results reveal that while LTASS was very similar across languages, deviations were observed between LTASS derived from the human speech and AI speech data compared to ILTASS. Specifically, measured LTASS demonstrated a reduced 500 Hz peak in contrast to ILTASS. This research underscores the importance of accounting for spectral variations introduced during the recording process in the field of speech and hearing research. It also emphasizes the importance of standardized recording protocols to enhance the precision of hearing technologies.

A Review of Machine Learning Approaches for the Personalization of Amplification in Hearing Aids.

This paper provides a review of various machine learning approaches that have appeared in the literature aimed at individualizing or personalizing the amplification settings of hearing aids. After stating the limitations associated with the current one-size-fits-all settings of hearing aid prescriptions, a spectrum of studies in engineering and hearing science are discussed. These studies involve making adjustments to prescriptive values in order to enable preferred and individualized settings for a hearing aid user in an audio environment of interest to that user. This review gathers, in one place, a comprehensive collection of works that have been conducted thus far with respect to achieving the personalization or individualization of the amplification function of hearing aids. Furthermore, it underscores the impact that machine learning can have on enabling an improved and personalized hearing experience for hearing aid users. This paper concludes by stating the challenges and future research directions in this area.

Effect of changes in the hearing aid subsidy on the prevalence of hearing loss in South Korea.

South Korea's National Health Insurance has provided hearing aids to registered individuals with hearing disabilities since 1989. In 2015, hearing aid subsidies increased to approximately US$1,000. This study aimed to understand hearing loss categories in Korea by analyzing patients between 2010 and 2020 and the effect of the 2015 hearing aid policy change on the prevalence of hearing loss. The participants were patients registered on the National Health Insurance Service database from 2010 to 2020 with hearing loss. A total of 5,784,429 patients were included in this study. Hearing loss was classified into conductive, sensorineural, and other categories. Patients with hearing loss were classified according to the International Classification of Diseases diagnostic code. Disability diagnosis and hearing aid prescription were defined using the National Health Insurance Disability and Hearing Aid Code. The increase in hearing aid prescriptions and hearing disability registrations following the subsidy increase impacts hearing loss prevalence. Hearing aid prescription and hearing disability were found to have an effect on increasing hearing loss prevalence in univariate and multivariate analyses. The r-value of each analysis exceeded 0.95. Other hearing losses increased rapidly after the increased subsidy. A hearing-impaired individual must be diagnosed with a hearing disability and prescribed a hearing aid to receive the subsidy. The prevalence of hearing loss was affected by increased hearing disabilities following changes in the hearing aid subsidy and the number of people prescribed hearing aids. Therefore, caution should be exercised when studying hearing loss prevalence over mid-long-term periods.

Impact of hearing aid technology level at first-fit on self-reported outcomes in patients with presbycusis: a randomized controlled trial.

To provide clinical guidance in hearing aid prescription for older adults with presbycusis, we investigated differences in self-reported hearing abilities and hearing aid effectiveness for premium or basic hearing aid users. Secondly, as an explorative analysis, we investigated if differences in gain prescription verified with real-ear measurements explain differences in self-reported outcomes. The study was designed as a randomized controlled trial in which the patients were blinded towards the purpose of the study. In total, 190 first-time hearing aid users (>60years of age) with symmetric bilateral presbycusis were fitted with either a premium or basic hearing aid. The randomization was stratified on age, sex, and word recognition score. Two outcome questionnaires were distributed: the International Outcome Inventory for Hearing Aids (IOI-HA) and the short form of the Speech, Spatial, and Qualities of Hearing Scale (SSQ-12). In addition, insertion gains were calculated from real-ear measurements at first-fit for all fitted hearing aids. Premium hearing aid users reported 0.7 (95%CI: 0.2; 1.1) scale points higher total SSQ-12 score per item and 0.8 (95%CI: 0.2; 1.4) scale points higher speech score per item, as well as 0.6 (95%CI: 0.2; 1.1) scale points higher qualities score compared to basic-feature hearing aid users. No significant differences in reported hearing aid effectiveness were found using the IOI-HA. Differences in the prescribed gain at 1 and 2kHz were observed between premium and basic hearing aids within each company. Premium-feature devices yielded slightly better self-reported hearing abilities than basic-feature devices, but a statistically significant difference was only found in three out of seven outcome variables, and the effect was small. The generalizability of the study is limited to community-dwelling older adults with presbycusis. Thus, further research is needed for understanding the potential effects of hearing aid technology for other populations. Hearing care providers should continue to insist on research to support the choice of more costly premium technologies when prescribing hearing aids for older adults with presbycusis. Clinical Trial Registration: https://register.clinicaltrials.gov/, identifier NCT04539847.

Investigation of hearing aid fitting according to the national acoustic laboratories’ prescription for non-linear hearing aids and the desired sensation level methods in Japanese speakers: a crossover-controlled trial

ObjectiveSome studies have directly compared the National Acoustic Laboratories’ prescription for non-linear hearing aids (HAs) version 2 (NAL-NL2) and Desired Sensation Level for non-linear HAs version 5 (DSLv5), although none were performed in Japan. As the Japanese language is a tonal language that has different linguistic characteristics than those of the studied languages, we compared the outcomes of the NAL-NL2 and DSLv5 in hearing-impaired Japanese participants. MethodsA crossover-controlled trial was conducted on 18 first-time HA users with bilateral moderate sensorineural hearing loss. Participants wore HAs adjusted with each prescriptive method for four weeks. The prescriptions were assessed using speech discrimination testing and the abbreviated profile of hearing aid benefit (APHAB). Consequently, participants were asked to select their preferred prescription and determine which was better for “listening to a conversation” and when “noisy.” ResultsThe mean DSLv5 real ear insertion gain for an input level of 65 dB sound pressure level (SPL) was higher than that of the NAL-NL2 at 250 and 500 Hz. The average speech discrimination score was 78 ± 14% at a 65-dB SPL and 75 ± 17% at an 80-dB SPL for the NAL-NL2, and 79 ± 11% at a 65-dB SPL and 77 ± 17% at an 80-dB SPL for the DSLv5. These differences were not significant. No significant differences were observed in APHAB subscale scores between the two prescription methods. Ultimately, 11 (61%) and 7 (39%) participants preferred the NAL-NL2 and DSLv5, respectively, with no significant differences. ConclusionAlthough the gain of the NAL-NL2 is smaller than that of the DSLv5, both had the same hearing effect. Therefore, the NAL-NL2 may be more useful than the DSLv5 in Japanese.

Task-Dependent Effects of Signal Audibility for Processing Speech: Comparing Performance With NAL-NL2 and DSL v5 Hearing Aid Prescriptions at Threshold and at Suprathreshold Levels in 9- to 17-Year-Olds With Hearing Loss.

Hearing aid fitting formulas intended for the pediatric population can differ by 6 to 25 dB in prescribed output across frequency leading to large variations in aided audibility. Children perceive these differences and have expressed preferences that favor more audibility for quiet speech and less audibility for noisy speech. In this study, the effect of variations in audibility consistent with hearing aid fittings for children was examined. Sixteen children and adolescents (9-17 years) with mild-to-moderate hearing loss participated. Hearing aids programed to National Acoustic Laboratories or Desired Sensation Level v5.0a targets were fitted to each participant. Also, separate programs with and without a low-level adaptive gain feature were provided with each prescription. Speech reception threshold (SRT) was measured as well as performance for four suprathreshold auditory tasks that increased in cognitive demand. These tasks were word recognition, nonword detection, multiword recall, and rapid word learning. A significant effect of fitting formula, but not low-level or adaptive gain, was observed for SRT. Significant effects of presentation level, fitting formula, and low-level gain were observed for word recognition. The effect of presentation level was significant for nonword detection, multiword recall, and rapid word learning but no other main effects or interactions were significant. Finally, word recognition and nonword detection increased significantly with audibility while multiword recall and word learning did not. The results suggest that audibility assists with the initial perception of auditory input but plays a smaller role in memory formation and learning.

The trend in adoption of hearing aids following changes in provision policy in South Korea

The Korean government started to cover part of the price of hearing aids ($200) for individuals with hearing disabilities in 1997, and the reimbursement for a hearing aid increased in 2005 ($300) and again in 2015 ($1000). The aim of this study was to evaluate the annual trend of newly-registered individuals with hearing disability according to the changes of the hearing aid provision scheme. Subjects with newly-registered hearing disabilities were assessed using Korean National Health Insurance Service (KNHIS) data from January 1, 2004, to December 31, 2018. A total of 271,742 individuals were newly registered during the index period. Records of hearing aid prescriptions and hearing aid subsidies were used to assess the adoption of hearing aids. This study also assessed the intervals between registration of hearing disability and the adoption of hearing aids, as well as the number of hearing aid subsidies provided. From 2004 to 2009 there was a slight increase in the number of individuals newly registered with hearing disabilities, and from 2011 to 2015, the number showed a tendency to decrease. Then, from 2015, the number of individuals with hearing disabilities increased abruptly, and the proportion of subjects receiving hearing aid subsidies also increased. Between 2004 and 2018, the time interval from hearing disability registration to hearing aid adoption showed a decreasing trend. We conclude that the annual number of individuals with newly-registered hearing disabilities is affected by the level of the hearing aid subsidy, and there is much unregistered or unaddressed hearing loss prior to the introduction of realistic hearing aid provision.

Age Differences in Speech Perception in Noise and Sound Localization in Individuals With Subjective Normal Hearing.

Hearing loss in old age, which often goes untreated, has far-reaching consequences. Furthermore, reduction of cognitive abilities and dementia can also occur, which also affects quality of life. The aim of this study was to investigate the hearing performance of seniors without hearing complaints with respect to speech perception in noise and the ability to localize sounds. Results were tested for correlations with age and cognitive performance. The study included 40 subjects aged between 60 and 90 years (mean age: 69.3 years) with not self-reported hearing problems. The subjects were screened for dementia. Audiological tests included pure-tone audiometry and speech perception in two types of background noise (continuous and amplitude-modulated noise) which was either co-located or spatially separated (multi-source noise field, MSNF) from the target speech. Sound localization ability was assessed and hearing performance was self-evaluated by a questionnaire. Speech in noise and sound localization was compared with young normal hearing adults. Although considering themselves as hearing normal, 17 subjects had at least a mild hearing loss. There was a significant negative correlation between hearing loss and dementia screening (DemTect) score. Speech perception in noise decreased significantly with age. There were significant negative correlations between speech perception in noise and DemTect score for both spatial configurations. Mean SRTs obtained in the co-located noise condition with amplitude-modulated noise were on average 3.1 dB better than with continuous noise. This gap-listening effect was severely diminished compared to a younger normal hearing subject group. In continuous noise, spatial separation of speech and noise led to better SRTs compared to the co-located masker condition. SRTs in MSNF deteriorated in modulated noise compared to continuous noise by 2.6 dB. Highest impact of age was found for speech perception scores using noise stimuli with temporal modulation in binaural test conditions. Mean localization error was in the range of young adults. Mean amount of front/back confusions was 11.5% higher than for young adults. Speech perception tests in the presence of temporally modulated noise can serve as a screening method for early detection of hearing disorders in older adults. This allows for early prescription of hearing aids.

Prognostic factors in non-organic hearing loss in children

Objective Exploring factors that predict a favourable clinical outcome in non-organic hearing loss (NOHL) in children. NOHL is defined as a subjective hearing loss without correlation in objective measures. Design Retrospective analysis of all childrens’ data with the diagnosis NOHL seen between 2005 and 2017 at a tertiary referral centre. Study sample Sixty-seven children (44 female, 23 male; mean age 11.26 years) were included. Statistical analyses included descriptive statistics, logistic regression, correlations, and Mann–Whitney U tests. Results A quarter of the children (17/67) had been provided previously with hearing aids without objective sensorineural hearing loss. Having been provided with hearing aids before the first visit to our clinic lowered the chance of normal hearing at the final visit by 76%. The prescription of hearing aids was significantly more likely in girls. Children provided with hearing aids were significantly older than those without and the time span between the first occurrence of the NOHL and first presentation at our department was longer than in children not provided with hearing aids. Conclusions In cases of NOHL, hearing aid prescription is not indicated and significantly lowers a child’s chance of full recovery and, thus, should not be prescribed unless NOHL is ruled out.

Uni- and bilateral spectral loudness summation and binaural loudness summation with loudness matching and categorical loudness scaling

Objective Current hearing aid prescription rules assume that spectral loudness summation decreases with hearing impairment and that binaural loudness summation is independent of hearing loss and signal bandwidth. Previous studies have shown that these assumptions might be incorrect. Spectral loudness summation was measured and compared for loudness scaling and loudness matching. Design In this study, the effect of bandwidth on binaural summation was investigated by comparing loudness perception of low-pass filtered, high-pass filtered, and broadband pink noise at 35 Categorical Units for both unilateral and bilateral presentation. Study sample Sixteen hearing-impaired listeners. Results The results show that loudness differences between the three signals are different for bilateral presentation than for unilateral presentation. In specific, binaural loudness summation is larger for the low-pass filtered pink noise than for the high-pass filtered pink noise. Finally, individual variability in loudness perception near loudness discomfort level was found to be very large. Conclusions Loudness matching is offered as a fast and reliable method to measure individual loudness perception. As discomfort with loud sounds is one of the major problems encountered by hearing aid users, measurement of individual loudness perception could improve hearing aid fitting substantially.

Using attribution theory to explore the reasons adults with hearing loss do not use their hearing aids.

Hearing aids are an effective treatment for individuals with hearing loss that have been shown to dampen (and sometime ameliorate) the negative effects of hearing loss. Despite the devices' efficacy, many reject hearing aids as a form of treatment. In the present qualitative study, we explored the reasons for hearing aid non-use in the United States that emerged from the stories of adults with hearing loss who do not to utilize hearing aids. We specifically used thematic analysis in concert with an attribution theory framework to identify and analyze recurring themes and reasons throughout these individuals' narratives. A total of nine themes describing reasons of hearing aid non-use emerged. Four reasons were internally motivated: (1) non-necessity, (2) stigmatization, (3) lack of integration into daily living, and (4) unreadiness due to lack of education; five reasons were externally motivated: (5) discomfort, (6) financial setback, (7) burden, (8) professional distrust, and (9) priority setting. These findings contribute to the field of hearing healthcare by providing professionals with insight into reasons that people across the provided when recounting their experiences following the diagnosis of hearing loss, prescription for hearing aids, and their hearing aid non-use. These findings are an important step toward the development of more effective, person-centered hearing healthcare that can best address these individuals' concerns and expectations surrounding hearing loss and hearing aids.

Evaluation of Universal Newborn Hearing Screening and follow-up

Universal newborn hearing screening (UNHS) was established in Germany in 2009. Even compliance was tested in early studies, there is little knowledge regarding the follow-up examination of children with suspected hearing disorder. A retrospective evaluation was performed in 570cases of children who failed newborn hearing screening for the years between 2009-2016. Hearing deficiency was defined as having a hearing threshold ≥ 35 dB. Compliance with national guidelines was checked. Every child received brainstem evoked response audiometry (BERA). Permanent hearing disorder was found in 24 %, of whom about half (51 %) had an inner ear hearing loss (of these in 73 % bilateral). Only 27 % of high risk children born in peripheral hospitals were tested immediately by the envisaged automated auditory brainstem response (AABR) method. They often presented tardy, leading to a delayed diagnosis and therapy. Children tracked by the Bavarian health office presented little earlier but had less cases who were lost to follow-up. In 93 % a diagnosis was made during first examination and therapy (e. g. prescription of hearing aids) initiated on average within four months age. The rate of deafness corresponded with national averages. The quality of primary screenings is crucial in revealing problems and avoiding delay in dealing with them.

Hearing Aid Self-Adjustment: Effects of Formal Speech-Perception Test and Noise.

While listening to recorded sentences with a sound-field level of 65 dB SPL, 24 adults with hearing-aid experience used the “Goldilocks” explore-and-select procedure to adjust level and spectrum of amplified speech to preference. All participants started adjustment from the same generic response. Amplification was provided by a custom-built Master Hearing Aid with online processing of microphone input. Primary goals were to assess the effects of including a formal speech-perception test between repeated self-adjustments and of adding multitalker babble (signal-to-noise ratio +6 dB) during self-adjustment. The speech test did not affect group-mean self-adjusted output, which was close to the National Acoustics Laboratories’ prescription for Non-Linear hearing aids. Individuals, however, showed a wide range of deviations from this prescription. Extreme deviations at the first self-adjustment fell by a small but significant amount at the second. The multitalker babble had negligible effect on group-mean self-selected output but did have predictable effects on word recognition in sentences and on participants’ opinion regarding the most important subjective criterion guiding self-adjustment. Phoneme recognition in monosyllabic words was better with the generic starting response than without amplification and improved further after self-adjustment. The findings continue to support the efficacy of hearing aid self-fitting, at least for level and spectrum. They do not support the need for inclusion of a formal speech-perception test, but they do support the value of completing more than one self-adjustment. Group-mean data did not indicate a need for threshold-based prescription as a starting point for self-adjustment.

Incidence and Risk of Various Disorders of the External Ear in Patients With Hearing Aids Treated in ENT Practices in Germany.

The aim of the study was to investigate the relationship between the presence of a hearing aid (HA) and the occurrence of various disorders of the external ear, using data from ear, nose, and throat (ENT) practices in Germany from a nationwide, representative practice database. In the period between 2012 and 2016, the incidences of disorders of the external ear (ICD-10 groups H60 and H61) in patients with HA prescriptions were compared retrospectively with a control group without HA prescriptions (1:1 matching). A total of 20,127 patients with HA prescriptions were compared with 20,127 controls. The highest 12-month incidences (HA vs. controls) were determined for "Impacted cerumen" (H61.2) (16.5% vs. 4.2%), "Unspecified otitis externa" (H60.9) (2.6% vs. 1.2%) and 'Acute noninfective otitis externa' (H60.5) (2.3% vs. 0.7%). The most significant risk increases for HA wearers were found for "Abscess of external ear' (H60.0, OR 10.03), "Other otitis externa' (H60.8, OR 6.00), and "Impacted cerumen' (H61.2, OR 4.55). A smaller risk increase was found for "Cholesteatoma of external ear' (H60.4, OR 2.26), among others. In HA wearers, the risk of developing almost all of the diagnoses reviewed is significantly increased, especially for external auditory canal (EAC) furuncle, chronic otitis externa, and impacted cerumen. This study provides the first epidemiological evidence for HA as a risk factor for the rare EAC cholesteatoma.

A Machine Learning Approach to Fitting Prescription for Hearing Aids

A successful Hearing-Aid Fitting (HAF) is more than just selecting an appropriate HearingAid (HA) device for a patient with Hearing Loss (HL). The initial fitting is given by the prescriptionbased on user’s hearing loss; however, it is often necessary for the audiologist to readjust someparameters to satisfy the user demands. Therefore, in this paper, we concentrated on a new applicationof Neural Network (NN) combined with a Transfer Learning (TL) strategy to develop a fittingalgorithm with the prescription database for hearing loss and readjusted gain to minimize the gapbetween fitting satisfaction. As prior information, we generated the data set from two popularhearing-aid fitting software, then fed the training data to our proposed model, and verified theperformance of the architecture. Pondering real life circumstances, where numerous fitting recordsmay not always be accessible, we first investigated the number of minimum fitting records requiredfor possible sufficient training. After that, we evaluated the performance of the proposed algorithmin two phases: (a) NN with refined hyper parameter showed enhanced performance in compareto state-of-the-art DNN approach, and (b) the TL approach boosted the performance of the NNalgorithm in a broad way. Altogether, our model provides a pragmatic and promising tool for HAF.

Evaluating human neural envelope coding as the basis of speech intelligibility in noise

Models of speech intelligibility that accurately reflect human listening performance across a broad range of background-noise conditions are clinically important (e.g., for deriving hearing-aid prescriptions, and optimizing cochlear-implant signal processing). A leading hypothesis in the field is that internal representations of envelope information ultimately determine intelligibility. However, this hypothesis has not been tested neurophysiologically. Here, we address this gap by combining human electroencephalography (EEG) with simultaneous perceptual intelligibility measurements. First, we derive a neural envelope-coding metric (ENVneural) from EEG responses to speech in multiple levels of stationary noise, and identify a mapping between the neural metric and corresponding speech intelligibility. Then, using the same mapping, we use only EEG measurements to test whether ENVneural is predictive of speech intelligibility in novel background-noise conditions and in the presence of linear and non-linear distortions. Preliminary results suggest that neural envelope coding can predict speech intelligibility to varying degrees for different realistic listening conditions. These results inform modeling approaches based on neural coding of envelopes, and may lead to the future development of physiological assays for characterizing individual differences in speech-in-noise perceptual abilities.

Beyond motivation: identifying targets for intervention to increase hearing aid use in adults

Objective: The present study investigated: (a) how motivated patients are to use their hearing aid, and (b) whether post-motivational variables (e.g. action planning, coping planning) have anything to offer in terms of developing interventions to boost hearing aid use.Design: participants completed a questionnaire designed to tap Health Action Process Approach constructs prior to their hearing aid prescription and fitting. Study sample: Sixty-seven patients attending NHS audiology clinics.Results: Participants reported very strong intentions to use hearing aids (Median = 7.00 Q1 and Q3 = 6.67, 7.00, on a +1 to +7 scale) and high self-efficacy (Median = 7.00, Q1 and Q3 = 6.00, on a +1 to +7 scale) leaving little room for improvement. In contrast, participants reported moderate levels of post-motivational variables (action planning Median = 4.25, Q1 and Q3 = 1.13, 7.00 and coping planning Median = 2.75, Q1 and Q3 = 1.00, both measured on +1 to +7 scales) thereby showing significant scope for change.Conclusions: Future interventions to increase hearing aid use should focus on ensuring that patients’ motivation is translated into action, rather than further trying to boost motivation.

How to Optimally Fit a Hearing Aid for Bimodal Cochlear Implant Users: A Systematic Review.

Bimodal hearing has shown to improve speech recognition in quiet and in noise and to improve sound localization compared with unilateral cochlear implant (CI) use alone. Fitting the CI and hearing aid (HA) separately has been described well, but HA fitting procedures for bimodal CI users are not well researched or widely accepted. The aim of the present study was to systematically review the literature on the effect of different HA fitting strategies on auditory performance in bimodal CI users. Original articles, written in English, were identified through systematic searches in Medline (OvidSP), Embase, Web of Science, Scopus, CINAHL, Cochrane, PubMed publisher, and Google Scholar. The quality of the studies was assessed on five aspects: methodologic quality (with the methodological index for nonrandomized studies score), number of subjects, quality of the description of contralateral hearing loss, quality of HA verification, and direct comparison of HA fitting procedures based on auditory performance. A total of 1665 records were retrieved, of which 17 were included for systematical reviews. Critical appraisal led to three high-quality studies, 10 medium-quality studies, and four low-quality studies. The results of the studies were structured according to four topics: frequency response, frequency translation/transposition, dynamic range compression, and loudness. In general, a bimodal benefit was found in most studies, using various strategies for the HA fitting. Using a standard prescription rule such as National Acoustics Laboratory formula-non-linear 1, National Acoustics Laboratory formula-non-linear 2, or desired sensation level is a good starting point in children and adults. Although a bimodal benefit was found in most studies, there is no clear evidence how certain choices in HA fitting contribute to optimal bimodal performance. A generally accepted HA prescription rule is an essential part of most fitting procedures used in the studies. Current evidence suggests that frequency lowering or transposition is not beneficial. Individual fine tuning based on loudness or general preference is often applied, but its additional value for auditory performance should be investigated more thoroughly. Good quality comparative studies are needed to further develop evidence-based fitting procedures in case of bimodal listening.

Phyllis M. Tookey Kerridge and the science of audiometric standardization in Britain.

The provision of standardized hearing aids is now considered to be a crucial part of the UK National Health Service. Yet this is only explicable through reference to the career of a woman who has, until now, been entirely forgotten. Dr Phyllis Margaret Tookey Kerridge (1901-1940) was an authoritative figure in a variety of fields: medicine, physiology, otology and the construction of scientific apparatus. The astounding breadth of her professional qualifications allowed her to combine features of these fields and, later in her career, to position herself as a specialist to shape the discipline of audiometry. Rather than framing Kerridge in the classic 'heroic-woman' narrative, in this article we draw out the complexities of her career by focusing on her pursuit of standardization of hearing tests. Collaboration afforded her the necessary networks to explore the intricacies of accuracy in the measurement of hearing acuity, but her influence was enhanced by her ownership of Britain's first Western Electric (pure-tone) audiometer, which she placed in a specially designed and unique 'silence room'. The room became the centre of Kerridge's hearing aid clinic that, for the first time, allowed people to access free and impartial advice on hearing aid prescription. In becoming the guardian expert and advocate of the audiometer, Kerridge achieved an objectively quantified approach to hearing loss that eventually made the latter an object of technocratic intervention.