Understanding speech-in-noise perception in adults: exploring the relative contributions of noise exposure, musical training and cognition

Theoretical thesis.Bibliography: pages 100-122.Chapter 1. Introduction -- Chapter 2. The effects of noise exposure and musical training on suprathreshold auditory processing and speech perception in noise -- Chapter 3. Working memory and extended high-frequency hearing in adults: diagnostic predictors of speech-in-noise perception -- Chapter 4. Attention and auditory processing skills in musicians -- Chapter 5. Case studies -- Chapter 6. Final discussion --Background. Current estimates are that between 5-15% of adults who present to medical or audiology clinics for hearing assessment, with concerns about difficulty understanding speech in background noise, are found to have normal pure-tone audiometric thresholds. Al though there is consensus amongst researchers that the audiogram inadequately reflects functional everyday listening, it remains unclear why, within the population of normal - hearing listeners, some people experience greater than expected perceptual difficulties. One suggestion is that excessive noise exposure may cause cochlear synaptopathy in humans, and subsequently lead to suprathreshold auditory processing and speech-in-noise difficulties prior to a clinical diagnosis of hearing loss. It has also been suggested that musical training may ameliorate any deficits arising from noise exposure, by enhancing speech perception in challenging listening environments, but there is debate as to whether such a 'musician advantage' is related to superior neural encoding of sound and/or higher order cognitive processes.Aims and objectives. The overarching goal of this thesis was to understand why some adults in their mid - years, despite having normal or 'near - normal' hearing thresholds, experience greater than expected difficulty understanding speech in noisy environments. Three studies were undertaken. Study 1 aimed to: (i) investigate whether noise exposure was associated with diminished auditory processing skills, including speech - in - noise perception ; and (ii) explore whether musical training is associated with improvements in aspects of auditory processing and counteracted any negative impacts of noise exposure. Study 2 aimed to : (i) identify the main factors that differentiated listeners with regard to their speech-in-noise perception; (ii) develop a model that predicted speech-in-noise difficulties; and (iii) evaluate the model's effectiveness as a 'diagnostic criterion'. Study 3 aimed to determine behavioural and physiological evidence of the 'musician advantage' ...1 online resource (xiv, 147 pages) illustration

Factors affecting reliability and validity of self-directed automatic in situ audiometry: implications for self-fitting hearing aids

Background: A reliable and valid method for the automatic in situ measurement of hearing thresholds is a prerequisite for the feasibility of a self-fitting hearing aid, whether such a device becomes an automated component of an audiological management program or is fitted by the user independently of a clinician. Issues that must be addressed before implementation of the procedure into a self-fitting hearing aid include the role of real-ear-to-dial difference correction factors in ensuring accurate results and the ability of potential users to successfully self-direct the procedure. Purpose: The purpose of this study was to evaluate the reliability and validity of an automatic audiometry algorithm that is fully implemented in a wearable hearing aid, to determine to what extent reliability and validity are affected when the procedure is self-directed by the user, and to investigate contributors to a successful outcome. Research Design: Design was a two-phase correlational study. Study Sample: A total of 60 adults with mild to moderately severe hearing loss participated in both studies: 20 in Study 1 and 40 in Study 2. Twenty-seven participants in Study 2 attended with a partner. Participants in both phases were selected for inclusion if their thresholds were within the output limitations of the test device. Data Collection and Analysis: In both phases, participants performed automatic audiometry through a receiver-in-canal, behind-the-ear hearing aid coupled to an open dome. In Study 1, the experimenter directed the task. In Study 2, participants followed a set of written, illustrated instructions to perform automatic audiometry independently of the experimenter, with optional assistance from a lay partner. Standardized measures of hearing aid self-efficacy, locus of control, cognitive function, health literacy, and manual dexterity were administered. Statistical analysis examined the repeatability of automatic audiometry; the match between automatically and manually measured thresholds; and contributors to successful, independent completion of the automatic audiometry procedure. Results: When the procedure was directed by an audiologist, automatic audiometry yielded reliable and valid thresholds. Reliability and validity were negatively affected when the procedure was self-directed by the user, but the results were still clinically acceptable: test-retest correspondence was 10 dB or lower in 97% of cases, and 91% of automatic thresholds were within 10 dB of their manual counterparts. However, only 58% of participants were able to achieve a complete audiogram in both ears. Cognitive function significantly influenced accurate and independent performance of the automatic audiometry procedure; accuracy was further affected by locus of control and level of education. Several characteristics of the automatic audiometry algorithm played an additional role in the outcome. Conclusions: Average transducer- and coupling-specific correction factors are sufficient for a self-directed in situ audiometry procedure to yield clinically reliable and valid hearing thresholds. Before implementation in a self-fitting hearing aid, however, the algorithm and test instructions should be refined in an effort to increase the proportion of users who are able to achieve complete audiometric results. Further evaluation of the procedure, particularly among populations likely to form the primary audience of a self-fitting hearing aid, should be undertaken

Acoustic Simulation Using 3d Modeling of the Development of a Super-directional System, past, Present and Future

It is well established that modern directional microphones in hearing aids provide listeners with an improved speech understanding in noise. De-spite this, the impact of directional microphones in real life conditions is limited. In fact, hearing in noise remains one of the biggest problems for hearing aid users. Fortunately, recent developments in super-directional technology, at least in laboratory settings, promise to deliver significant benefits to hearing aid users. Experiments suggest large improvements in speech understanding in noise and significant preference for highly directional systems. This advantage is often extrapolated to suggest equal advantages in real world listening situations. However, it is increasingly apparent that hearing in noise entails various complex tasks for the listener. Consequently, super-directional technology may be advantageous in some situations but may also have some limitations in its usage. Here we present a discussion of super-directional microphone technology based on several studies. In our research we have examined various factors that influence benefit such as beam width design, adaptation speed, preservation of spatial cues, vent sizes, acoustic scene, and reverberation. Our evidence appears to be confounded by individual characteristics of the listener such as age, hearing loss, personality traits, and cognition. All these factors combined will guide our discussions and thoughts about future research and development of super-directional system