The perception of sound by the human auditory system is a complex process and its understanding is of major importance for many applications in our everyday life, e.g., the estimation of noise emissions, or the development of hearing aids. The mechanics of the human auditory system and the perception of sound are investigated in psychoacoustics. Psychoacoustic studies and measures help to characterize the perception of sound. The scope of this thesis is the perception of loudness and sound intensity. Loudness perception, among other aspects, depends on temporal and spectral properties of a sound. In the present thesis temporal and spectral effects of loudness as well as the changing of the perception of loudness and sound intensity in hearing-impaired listeners are investigated. Especially regarding the loudness of subcritical noise bands, the presented results are challenging for current ideas of modeling loudness perception.
Abstract: Normal hearing is typically defined by threshold audibility, or the loudness of sounds that an individual is able to hear. This convention exists despite the fact that everyday communication relies on extracting and interpreting features of supra-threshold sound. Many normal-hearing listeners struggle to perform certain supra-threshold auditory tasks, and debate persists as to whether such difficulties originate from deficits in cognitive processing or in peripheral, sensory encoding. In this work, we show that there are large individual differences among normal-hearing adults (18 to 55 years), who were asked to report a stream of digits located directly ahead in a simulated rectangular room. Simultaneous, competing masker digit streams were simulated at locations 15° left and right of center, and the level of reverberation was adjusted to vary task difficulty. Performance was best in the anechoic condition and worst in the high-reverberation condition, but listeners nearly always reported a digit from one of the three competing streams, showing that reverberation did not render the digits unintelligible. Most importantly, inter-subject differences were extremely large. These differences were not significantly correlated with age, memory span, or hearing status. They were, however, correlated with behavioral differences in the ability to detect small frequency modulations in pure tones and with the strength of the frequency following response (FFR), a physiological measure of spectro-temporal detail encoding in supra-threshold sounds early in the auditory pathway. The decomposition of the FFR into envelope and carrier components shows that envelope frequency following is the preferred cue for completing the spatial attention task, but it degrades with early aging. As a result, older listeners depend more on carrier phase locking cues than younger people. These results suggest that differences in peripheral encoding help explain individual differences in the ability to communicate in challenging settings, but that aging also has a separate, dissociable effect on early encoding in the auditory system. Tests like these may help tease apart contributions of peripheral and central deficits to communication impairments, ultimately leading to new approaches for helping listeners cope with complex listening environments.
Millions of Americans experience some degree of hearing loss. The Social Security Administration (SSA) operates programs that provide cash disability benefits to people with permanent impairments like hearing loss, if they can show that their impairments meet stringent SSA criteria and their earnings are below an SSA threshold. The National Research Council convened an expert committee at the request of the SSA to study the issues related to disability determination for people with hearing loss. This volume is the product of that study. Hearing Loss: Determining Eligibility for Social Security Benefits reviews current knowledge about hearing loss and its measurement and treatment, and provides an evaluation of the strengths and weaknesses of the current processes and criteria. It recommends changes to strengthen the disability determination process and ensure its reliability and fairness. The book addresses criteria for selection of pure tone and speech tests, guidelines for test administration, testing of hearing in noise, special issues related to testing children, and the difficulty of predicting work capacity from clinical hearing test results. It should be useful to audiologists, otolaryngologists, disability advocates, and others who are concerned with people who have hearing loss.
(cont.) However, further results in the third and fourth studies suggested a role for harmonic resolvability in pitch discrimination, inconsistent with the lack of dependence on resolvability of the modified autocorrelation model. In normal-hearing subjects at high stimulus levels and in hearing-impaired subjects, a wider spacing between adjacent frequency components, related to a reduction in frequency selectivity, was required to yield accurate FO discrimination performance. Thus, resolved harmonics may be necessary for accurate FO encoding, and the pitch discrimination deficit associated with sensorineural hearing loss may be related to a reduction in frequency selectivity. These results support spectral or spectrotemporal pitch models that derive FO from resolved harmonics, or a place-dependent temporal model whereby peripheral filter bandwidths limit the range of detectable periodicities. Because spectral processing plays an important role in pitch discrimination, hearing-impaired and cochlear-implant listeners may benefit from hearing-aid fitting procedures and cochlear-implant processing algorithms that emphasize or enhance spectral place cues.
Spatial-hearing ability has been found to vary widely across listeners. A survey of the existing auditory-space perception literature suggests that three main types of factors may account for this variability: - physical factors, e.g., acoustical characteristics related to sound-localization cues, - perceptual factors, e.g., sensory/cognitive processing, perceptual learning, multisensory interactions, - and methodological factors, e.g., differences in stimulus presentation methods across studies. However, the extent to which these–and perhaps other, still unidentified—factors actually contribute to the observed variability in spatial hearing across individuals with normal hearing or within special populations (e.g., hearing-impaired listeners) remains largely unknown. Likewise, the role of perceptual learning and multisensory interactions in the emergence of a multimodal but unified representation of “auditory space,” is still an active topic of research. A better characterization and understanding of the determinants of inter-individual variability in spatial hearing, and of its relationship with perceptual learning and multisensory interactions, would have numerous benefits. In particular, it would enhance the design of rehabilitative devices and of human-machine interfaces involving auditory, or multimodal space perception, such as virtual auditory/multimodal displays in aeronautics, or navigational aids for the visually impaired. For this Research Topic, we have considered manuscripts that: - present new methods, or review existing methods, for the study of inter-individual differences; - present new data (or review existing) data, concerning acoustical features relevant for explaining inter-individual differences in sound-localization performance; - present new (or review existing) psychophysical or neurophysiological findings concerning spatial hearing and/or auditory perceptual learning, and/or multisensory interactions in humans (normal or impaired, young or older listeners) or other species; - discuss the influence of inter-individual differences on the design and use of assistive listening devices (rehabilitation) or human-machine interfaces involving spatial hearing or multimodal perception of space (ergonomy).
The International Symposium on Hearing is a prestigious, triennial gathering where world-class scientists present and discuss the most recent advances in the field of human and animal hearing research. The 2015 edition will particularly focus on integrative approaches linking physiological, psychophysical and cognitive aspects of normal and impaired hearing. Like previous editions, the proceedings will contain about 50 chapters ranging from basic to applied research, and of interest to neuroscientists, psychologists, audiologists, engineers, otolaryngologists, and artificial intelligence researchers.
