Scandinavian audiology. Supplementum最新文献

In recent years, findings that exposure to industrial chemicals may affect hearing and interact with noise brought to light a risk that had not been given substantial attention previously. The need for research becomes clear when the magnitude of the population of workers exposed to noise and chemicals and the number of potentially hazardous chemicals found in work environments are taken into consideration. The need for research is this area is further heightened by the fact that there are no guidelines or standards for combined exposures of chemical and physical agents. The present paper reviews the effects of combined exposures to chemicals and noise on hearing and examines study designs, hearing assessment alternatives, and strategies for the analysis of combined effects.

Distortion Product Otoacoustic Emissions (DPOAEs) shows a vulnerability to acoustic overstimulation that is easily detectable by changes in amplitude, frequency distribution and time course. The frequency-specific changes in DPOAE provide more information than the more general changes in click evoked otoacoustic emissions. In this work five anesthetized guinea pigs were examined for changes DPOAE after exposure to pure tones. The noise was a 110 dB SPL pure tones for 45 minutes and the fatiguing tone centered on the geometric mean (GM) of primaries or 2/3 of GM. The most measurable effects were obtained in the latter conditions. The main DP level reduction lasts about one hour after exposure, but the complete recovery is observable only after 24 hours. The frequency distribution of fatiguing effects on the DP- audiogram shows a remarkable fine tuning and a pattern like a low-pass filter. After four hours, in one guinea pig, it is observable an enhancement of the DP amplitude, compared to the pre-exposure level; in another guinea pig, a second overstimulation produced a more extensive and time-lasting effects than the first exposure.

The study examined the phonological processing skills in a group of adults who have acquired a severe hearing loss in adult life. These severely hearing-impaired individuals performed at a significantly lower level on the rhyme judgement tasks and the letter span task, but on a par with the control group on other cognitive tests. A correlation analysis showed that duration of hearing loss is negatively related to performance on the rhyme judgement tasks and letter span task. The results indicate that the phonological processing skills in individuals who have acquired a severe hearing loss in adult life deteriorates. The results are discussed with respect to theoretical and clinical implications.

The conceptual framework for describing an audiological communication handicap and its underlying processes is built in analogy to a biological, ecological system and uses the following primary concepts: interaction, internal milieu, preferendum (preferred communication features) and optimal resource utilization. From these primary concepts secondary concepts and processes are formulated: signal, message/dialogue and behavior are three levels of interaction; adjustment and release of mental resources are specifications for preferendum (influenced by contextual and social conditions); specificity and facilitation underlie optimal resource utilization. The internal environment contains afferent, central and efferent speech and language processing, cognitive and emotional processes. The main components of audiology and rehabilitation (impairment, disability, handicap) are deduced from these concepts and processes. Examples of studies based on this conceptual framework are presented briefly. These include an environmental test chamber where realistic acoustic environments and communication situations can be directly studied, and a rehabilitation programme based on tutorial education for structured interaction at the behaviour level between hearing-impaired and normal-hearing persons. A vibratory-based event localization system for deaf-blind is described which improves specificity and thereby mental resource utilization.

Changes in service delivery triggered by current conceptualizations of rehabilitation require an accompanying paradigm shift in the approaches used to evaluate the effectiveness of intervention programs in audiological rehabilitation. The present article outlines three fundamental principles of contemporary rehabilitative audiology that have implications concerning the way that audiological rehabilitation services should be conceived and dispensed, as well as the way in which comprehensive evaluative research investigations should be designed and conducted. Traditional treatment efficacy paradigms used to assess the effectiveness of intervention programs in rehabilitative audiology are critiqued. Finally, factors that should guide the development of comprehensive evaluative research paradigms which are consistent with current models of intervention in audiological rehabilitation are outlined.

Historically, auditory research has focused predominantly on how relatively simple acoustic signals are represented in the neuronal responses of the auditory periphery. However, in order to understand the neurophysiology underlying speech perception, the ultimate objective is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. This paper reviews three areas pertaining to the central auditory representation of speech: (1) the differences in neural representation of speech sounds at different levels of the auditory system, (2) the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and (3) the plasticity of speech-sound neural representation and speech perception.

The Equal Energy Hypothesis (EEH) is based on the assumption that hearing loss from a given exposure is proportional to the total energy of the exposure. A corollary of this assumption is the power of the exposure and the duration of the exposure are interchangeable. Studies of impulse and impact noise show that hearing loss does not follow the prediction of the EEH (Ward, 1986; Danielson et al., 1991). Thus, the following experiments were designed to assess the relative importance of the duration and peak level of impact noise in the production of hearing loss. Monaural chinchillas served as subjects. Their quiet thresholds were estimated before and after exposures using the evoked potential recorded from a chronic electrode in the inferior colliculus. The four groups of the "intensity" series were exposed for 7.5 hours to 200 msec impacts at 1 per second at levels of 113, 119, 125, and 131 dB peak equivalent SPL. The three groups of the "duration" series were exposed to the 125 dB impacts for either 1.9, 7.5, or 30 hours. With each dB increase in the "duration" series, there was approximately 1.7 dB of increase in hearing loss. For each dB increase in peak level above 125 dB, there was an average of 6.6 dB increase in hearing loss. The 125 dB exposure is just below the "critical level" where the mode of cochlear damage shifts to mechanical failure. The results are discussed in terms of "critical" level and implication for noise standards.

Research and issues related to cognitive diversity in deaf people will be reviewed that indicate how the visual-perceptual skills and cognitive processes of deaf people may be different from those in hearing people. It is suggested that deafness and the use of a sign language may selectively contribute to the development of such differences. Implications of the research and its limitations for enhancing the communication and educational experiences of deaf people are also discussed.

The increasing complexity of the non-linear signal processing of modern hearing aids makes the use of clinical assessment of hearing aid benefit more and more important. The paper discusses the general structure of such studies with regard to choice of test subjects, reference hearing aids and the advantage of double-blind and cross-over design. Assessment should contain at least the three dimensions: perceived hearing aid benefit (preferably including perceived sound quality and preference between test and reference aids), speech recognition in noise, and electroacoustic verification by means of real-ear measurements.

We review data from our laboratory related to a view of dyslexia as a biological disorder, or deficit, caused by both structural and functional brain abnormalities. The review is focused on central auditory processing in dyslexia, and the possibility that impairments in the auditory or acoustic features of the phonological code may be at the heart of the impairments seen in dyslexia. Three methodological approaches by which to investigate central auditory processing deficits are outlined: dichotic listening (DL) to consonant-vowel syllables; magnetic resonance imaging (MRI), and the use of event-related potentials (ERPs). Consonant-vowel syllable DL is a technique for probing the functional status of phonological processing areas in the superior temporal gyrus, particularly in the left hemisphere. MRI is a corresponding structural, or morphological, measure of anatomical abnormalities in the same brain region, particularly covering the planum temporale area. The ERP technique, and particularly the mismatch negativity (MMN) component, reveals cortical dysfunctions in sensory processing and memory related to basic acoustic events. For all three approaches, the dyslexic children were seen to differ from their control counterparts, including absence of modulation of the right ear advantage (REA), in DL through shifting of attention, smaller left-sided planum temporale asymmetry, and prolonged latency in the MMN ERP complex, particularly in the time-deviant stimulus condition.