Die Entwicklung der Audiologie - von Helmholtz bis heute.

On occasion of the 200th anniversary of the birthday of Hermann von Helmholtz the article presents a historical review on the development of audiology over the past two centuries. Modern audiology is considered to be a multidisciplinary field addressing clinical work and research on all aspects of hearing impairment, particularly prevention/protection, diagnostics and treatment of hearing problems as well as rehabilitation of patients with any degree of hearing loss. To cover all these subjects comprehensively would go beyond the scope of a journal article. Therefore, the review focuses on two of these domains, namely hearing research and diagnostic procedures as representatives for the other areas of audiology being equally important. The paper concludes with a brief look into the development of the organizational structures of audiology and a summary.

Assessment of hearing aid algorithms using a master hearing aid: the influence of hearing aid experience on the relationship between speech recognition and cognitive capacity.

OBJECTIVES: Model-based hearing aid development considers the assessment of speech recognition using a master hearing aid (MHA). It is known that aided speech recognition in noise is related to cognitive factors such as working memory capacity (WMC). This relationship might be mediated by hearing aid experience (HAE). The aim of this study was to examine the relationship of WMC and speech recognition with a MHA for listeners with different HAE. DESIGN: Using the MHA, unaided and aided 80% speech recognition thresholds in noise were determined. Individual WMC capacity was assed using the Verbal Learning and Memory Test (VLMT) and the Reading Span Test (RST). STUDY SAMPLE: Forty-nine hearing aid users with mild to moderate sensorineural hearing loss divided into three groups differing in HAE. RESULTS: Whereas unaided speech recognition did not show a significant relationship with WMC, a significant correlation could be observed between WMC and aided speech recognition. However, this only applied to listeners with HAE of up to approximately three years, and a consistent weakening of the correlation could be observed with more experience. CONCLUSIONS: Speech recognition scores obtained in acute experiments with an MHA are less influenced by individual cognitive capacity when experienced HA users are taken into account.

Functionality of hearing aids: state-of-the-art and future model-based solutions.

A review about technical and perceptual factors in hearing aid technology, research and development is provided, covering current commercial solutions, underlying models of hearing loss for usage in hearing devices and emerging future technical solutions for hearing aid functionalities. A chain of techniques has provided incremental, but steady increases in user benefit, e.g. in the fields of hearing aid amplification, feedback suppression, dynamic compression, noise reduction and situation adaptation. The models describing the perceptual consequences of sensorineural hearing impairment describe the effects on the acoustical level, the neurosensory level and the cognitive level and provide the framework for compensatory (or even substitutional) functions of hearing aids in terms of the attenuation component, the distortion component and the neural component of the hearing loss. A major factor is the requirement of a strong individualisation of hearing aid solutions calling for an appropriate assessment of the different sensorineural components of a hearing loss, especially with respect to bilateral and binaural hearing aid solutions.

Comparison of single-microphone noise reduction schemes: can hearing impaired listeners tell the difference?

OBJECTIVE: The perceived qualities of nine different single-microphone noise reduction (SMNR) algorithms were to be evaluated and compared in subjective listening tests with normal hearing and hearing impaired (HI) listeners. DESIGN: Speech samples added with traffic noise or with party noise were processed by the SMNR algorithms. Subjects rated the amount of speech distortions, intrusiveness of background noise, listening effort and overall quality, using a simplified MUSHRA (ITU-R, 2003 ) assessment method. STUDY SAMPLE: 18 normal hearing and 18 moderately HI subjects participated in the study. RESULTS: Significant differences between the rating behaviours of the two subject groups were observed: While normal hearing subjects clearly differentiated between different SMNR algorithms, HI subjects rated all processed signals very similarly. Moreover, HI subjects rated speech distortions of the unprocessed, noisier signals as being more severe than the distortions of the processed signals, in contrast to normal hearing subjects. CONCLUSIONS: It seems harder for HI listeners to distinguish between additive noise and speech distortions or/and they might have a different understanding of the term "speech distortion" than normal hearing listeners have. The findings confirm that the evaluation of SMNR schemes for hearing aids should always involve HI listeners.

Hearing aid fitting in older persons with hearing impairment: the influence of cognitive function, age, and hearing loss on hearing aid benefit.

PURPOSE: To examine the association of cognitive function, age, and hearing loss with clinically assessed hearing aid benefit in older hearing-impaired persons. METHODS: Hearing aid benefit was assessed using objective measures regarding speech recognition in quiet and noisy environments as well as a subjective measure reflecting everyday situations captured using a standardized questionnaire. A broad range of general cognitive functions such as attention, memory, and intelligence were determined using different neuropsychological tests. Linear regression analyses were conducted with the outcome of the neuropsychological tests as well as age and hearing loss as independent variables and the benefit measures as dependent variables. Thirty experienced older hearing aid users with typical age-related hearing impairment participated. RESULTS: Most of the benefit measures revealed that the participants obtained significant improvement with their hearing aids. Regression models showed a significant relationship between a fluid intelligence measure and objective hearing aid benefit. When individual hearing thresholds were considered as an additional independent variable, hearing loss was the only significant contributor to the benefit models. Lower cognitive capacity - as determined by the fluid intelligence measure - was significantly associated with greater hearing loss. Subjective benefit could not be predicted by any of the variables considered. CONCLUSION: The present study does not give evidence that hearing aid benefit is critically associated with cognitive function in experienced hearing aid users. However, it was found that lower fluid intelligence scores were related to higher hearing thresholds. Since greater hearing loss was associated with a greater objective benefit, these results strongly support the advice of using hearing aids regardless of age and cognitive function to counter hearing loss and the adverse effects of age-related hearing impairment. Still, individual cognitive capacity might be relevant for hearing aid benefit during an initial phase of hearing aid provision if acclimatization has not yet taken place.

A comparison of conventional and in-situ audiometry on participants with varying levels of sensorineural hearing loss.

BACKGROUND: In-situ audiometry is a hearing aid feature that enables the measurement of hearing threshold levels through the hearing instrument using the built-in sound generator and the hearing aid receiver. This feature can be used in hearing aid fittings instead of conventional pure-tone audiometry (PTA), particularly in places where no standard audiometric equipment is available. Differences between conventional and in-situ thresholds are described and discussed for some particular hearing aids. No previous investigation has measured and compared these differences for a number of current hearing aid models by various manufacturers across a wide range of hearing losses. PURPOSE: The purpose of this study was to perform a model-based comparison of conventionally and in-situ measured hearing thresholds. Data were collected for a range of hearing aid devices to study and generalize the effects that may occur under clinical conditions. RESEARCH DESIGN: Research design was an experimental and regression study. STUDY SAMPLE: A total of 30 adults with sensorineural hearing loss served as test persons. They were assigned to three subgroups of 10 subjects with mild (M), moderate to severe (MS), and severe (S) sensorineural hearing loss. INTERVENTION: All 30 test persons underwent both conventional PTA and in-situ audiometry with four hearing aid models by various manufacturers. DATA COLLECTION AND ANALYSIS: The differences between conventionally and in-situ measured hearing threshold levels were calculated and evaluated by an exploratory data analysis followed by a sophisticated statistical modeling process. RESULTS: At 500 and 1500 Hz, almost all threshold differences (conventional PTA minus in-situ data) were negative, i.e., in the low to mid frequencies, hearing loss was overestimated by most devices relative to PTA. At 4000 Hz, the majority of differences (7 of 12) were positive, i.e., in the frequency range above 1500 Hz, hearing loss was frequently underestimated. As hearing loss increased (M→MS→S), the effect of the underestimation decreased. At 500 and 1500 Hz, Resound devices showed the smallest threshold deviations, followed by Phonak, Starkey, and Oticon instruments. At 4000 Hz, this observed pattern partly disappeared and Starkey and Oticon devices showed a reversed effect with increasing hearing loss (M→MS→S). Because of high standard errors for the estimates, only a few explicit rankings of the devices could be established based on significant threshold differences (5% level). CONCLUSIONS: Differences between conventional PTA and in-situ threshold levels may be attributed to (1) frequency, (2) device/hearing loss, and (3) calibration/manufacturer effects. Frequency effects primarily resulting in an overestimation of hearing loss by in-situ audiometry in the low and mid frequencies are mainly due to sound drain-off through vents and leaks. Device/hearing loss effects may be due to leakage as well as boundary effects because in-situ audiometry is confined to a limited measurement range. Finally, different calibration approaches may result in different offset levels between PTA and in-situ audiometry calibration. In some cases, the observed threshold differences of up to 10-15 dB may translate to varied hearing aid fittings for the same user depending on how hearing threshold levels were measured.

Development of a German reading span test with dual task design for application in cognitive hearing research.

OBJECTIVE: To report the development of a standardized German version of a reading span test (RST) with a dual task design. Special attention was paid to psycholinguistic control of the test items and time-sensitive scoring. We aim to establish our RST version to use for determining an individual's working memory in the framework of hearing research in German contexts. DESIGN: RST stimuli were controlled and pretested for psycholinguistic factors. The RST task was to read sentences, quickly determine their plausibility, and later recall certain words to determine a listener's individual reading span. RST results were correlated with outcomes of additional sentence-in-noise tests measured in an aided and an unaided listening condition, each at two reception thresholds. STUDY SAMPLE: Item plausibility was pre-determined by 28 native German participants. An additional 62 listeners (45-86 years, M = 69.8) with mild-to-moderate hearing loss were tested for speech intelligibility and reading span in a multicenter study. RESULTS: The reading span test significantly correlated with speech intelligibility at both speech reception thresholds in the aided listening condition. CONCLUSION: Our German RST is standardized with respect to psycholinguistic construction principles of the stimuli, and is a cognitive correlate of intelligibility in a German matrix speech-in-noise test.

A multi-site evaluation of a proposed test for verifying hearing aid maximum output.

The aim of this study was to evaluate a clinical test proposed to verify the output setting of hearing aids. Across three test sites, 56 bilaterally fitted hearing aid users were recruited. They answered questions about real-life loudness discomfort experiences and then completed the output verification test. Using an ascending method, a 1,500 kHz narrowband noise and a selection of broadband environmental noises were presented in 5 dB steps from 80 to 90 dB SPL. Response options included 'acceptably loud', and 'uncomfortably loud'. A swept pure tone presented at 90 dB SPL was also administered. Some loudness discomfort was reportedly experienced in real life by 82% of the participants. Generally, the test noises produced low specificity, with the 1,500 kHz narrowband noise being the best predictor of loudness discomfort experiences in real life, while the swept pure tone showed low sensitivity. Individual reactions to specific sounds and the test equipment and environment used are argued to affect the laboratory performance. A better understanding of these factors is needed before the test can be improved. an ser mejoradas.

The design of a project to assess bilateral versus unilateral hearing aid fitting.

Binaural hearing provides advantages over monaural in several ways, particularly in difficult listening situations. For a person with bilateral hearing loss, the bilateral fitting of hearing aids thus seems like a natural choice. However, surprisingly few studies have been reported in which the additional benefit of bilateral versus unilateral hearing aid use has been investigated based on real-life experiences. Therefore, a project has been designed to address this issue and to find tools to identify people for whom the drawbacks would outweigh the advantages of bilateral fitting. A project following this design is likely to provide reliable evidence concerning differences in benefit between unilateral and bilateral fitting of hearing aids by evaluating correlations between entrance data and outcome measures and final preferences.

The occlusion effect in unilateral versus bilateral hearing aids.

The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids.

Fitting strategies and candidature criteria for unilateral and bilateral hearing aid fittings.

In this paper, hearing aid fitting strategies are reviewed and candidature criteria for unilateral and bilateral fittings are discussed. Fitting strategies are primarily governed by the objectives of hearing aid fitting that can be set in different ways. Based on common goals, fitting strategies can be broken down into three stages: (1) basic fitting, (2) fine-tuning and (3) verification and validation. A fine-tuning concept basing on so-called meta-controllers is described and the issue of bilateral fitting strategies is discussed. In a first order approach, bilateral hearing aids can be fitted in parallel as unilateral aids, followed by bilateral fine-tuning, making sure that loudness is balanced and overall loudness is accepted. Parallel fitting of bilateral aids is more favourable than sequential fitting to avoid rejection because of a negative experience with unilateral amplification due to difficulties in disadvantageous listening situations. Candidature criteria are presented by means of a flow chart structuring the decision making process and arriving at the conclusion that bilateral fitting should be considered the normal case. If there is any doubt about the benefit of bilateral fitting, a trial with bilateral aids should be performed.

Occlusion effect of earmolds with different venting systems.

In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent cross-sectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher ("high OE" ear) than in the "low OE" ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.

Modeling relationships between various domains of hearing aid provision.

Various inventories have been developed to quantify the success of hearing aid provision. Though numerous parameters including initial measures (hearing disability, handicap) or 'outcome measures' (e.g. benefit, satisfaction and usage) are recorded, relationships and interactions among them are still unclear. A study applying a questionnaire addressing 11 domains relevant to amplification was conducted in order to generate different psychometric models with the AMOS software package for structural equation modeling. The models expose easily interpretable interactions and are helpful in understanding effects occurring with commonly used outcome measures: benefit reflects the difference between the aided and unaided condition but additionally comprises the importance of the hearing aid within a specific situation. Satisfaction is highly reliant on benefit. Usage is strongly dependent on the severity of hearing problems and therefore not appropriate in assessing the success of amplification. Moreover, the models help to predict the outcome of clinically used inventories (i.e. the Glasgow Hearing Aid Benefit Profile).