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.

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.

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.

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.