Hearing impairment and self-masking: listening during vocalization.

OBJECTIVES: To describe the masking effect of a vocalized [a:] on noise bands and speech in persons with mild-to-moderate hearing impairment (HI). DESIGN: The masked threshold of noise bands (250-8000 Hz), continuous discourse, and the amount of masking produced were determined. The maximal vocalization level was determined, that still allowed the subject to just follow the continuous discourse. STUDY SAMPLE: Twenty persons with sensory-neural HI, twelve with a high-frequency (HF) loss and eight with low-, mid-frequency or flat (LMF) loss. RESULTS: The [a:] gave a significantly higher masked threshold at 70 and 80 dBA vocalization for subjects with HF loss than for normal-hearing (NH) subjects, and somewhat higher thresholds than for those with LMF loss. The amount of masking produced was significantly smaller for subjects with HI than NH. CONCLUSIONS: It is important to consider masking effects of self-produced sounds in auditory rehabilitation, and in the future design of hearing aids.

Assessment of auditory brainstem function in lead-exposed children using stapedius muscle reflexes.

The purpose of this study was to investigate the neurological integrity and physiological status of the auditory brainstem tracts and nuclei in children with chronic lead (Pb) exposure using non-invasive acoustic stapedius reflex (ASR) measurements of afferent and efferent-neuromuscular auditory function. Following audiological examinations, uncrossed (ipsilateral) and crossed (contralateral) brainstem ASR responses were evoked by pure tone (500, 1000, and 2000 Hz), and broadband noise (bandwidth: 125-4000 Hz) stimulus activators. The ASR threshold (ASRT), amplitude growth, and decay/fatigue were measured by conventional clinical middle ear immittance methods in a group of Andean children (age range: 2-18 years) with a history of chronic environmental Pb exposure from occupational Pb glazing. Blood lead (PbB) levels of the study group (n=117) ranged from 4.0 to 83.7 µg/dL with a mean PbB level of 33.5 µg/dL (SD: 23.6; median: 33.0: CDC III Classification). The PbB distribution data indicated that 77.8% (n=91) of the children had PbB levels greater than the CDC action line of 10 µg/dL. Repeatable, normal ASRTs were elicited for ipsilateral (mean: ≤90 dB HL) and contralateral (mean: ≤97 dB HL) stimulation for each acoustic activator. Spearman Rho correlation analysis indicated no significant association between PbB level and ipsilateral or contralateral ASRT for any of the stimulus activators. The ASR amplitude growth results showed typical growth functions with no Pb-associated aberrations. No statistical association was found between ASR decay/adaptation (ASRD) and PbB level for any of the stimulus activators. The results of stapedius muscle reflex testing using several stimulus activators showed no significant relationship between PbB level and the physiological integrity of the auditory brainstem mediated ASR responses in children with chronic Pb exposure and elevated PbB levels.

On the problem of listening while talking.

The Gauffin and Sundberg technique of assessing masking during vocalization was modified and tested on 22 normal-hearing and 20 hearing-impaired subjects. The masking effect of the vocalized [a:] on narrow-band noise pulses (250-8,000 Hz) and on test reading was studied. The results showed that the female voice was about 4 dB more efficient in masking external speech compared to the male voice and that the female voice had a high-frequency bias of masking the narrow-band noise, whereas the male voice had a low-frequency bias. Subjects with hearing impairment in the high frequencies were particularly impaired by the masking caused by their own voice. The implications for multilogue conversations and auditory rehabilitation are discussed.

Self-masking: Listening during vocalization. Normal hearing.

What underlying mechanisms are involved in the ability to talk and listen simultaneously and what role does self-masking play under conditions of hearing impairment? The purpose of the present series of studies is to describe a technique for assessment of masked thresholds during vocalization, to describe normative data for males and females, and to focus on hearing impairment. The masking effect of vocalized [a:] on narrow-band noise pulses (250-8000 Hz) was studied using the maximum vocalization method. An amplitude-modulated series of sound pulses, which sounded like a steam engine, was masked until the criterion of halving the perceived pulse rate was reached. For masking of continuous reading, a just-follow-conversation criterion was applied. Intra-session test-retest reproducibility and inter-session variability were calculated. The results showed that female voices were more efficient in masking high frequency noise bursts than male voices and more efficient in masking both a male and a female test reading. The male had to vocalize 4 dBA louder than the female to produce the same masking effect on the test reading. It is concluded that the method is relatively simple to apply and has small intra-session and fair inter-session variability. Interesting gender differences were observed.

Imaging of the guinea pig cochlea following round window gadolinium application.

Precise, non-invasive determination of the aetiology and site of pathology of inner ear disorders is difficult. The aim of this study was to describe an alternative method for inner ear visualization, based on local application of the paramagnetic contrast agent gadolinium. Using a 4.7 T MRI scanner, high contrast images of all four cochlear turns were obtained 3.5 h after placing gadolinium on the round window membrane. Gadolinium cleared from the cochlea within 96 h. Auditory brainstem response measurements performed on a separate group of animals showed no significant threshold shifts after the application, indicating that gadolinium is non-toxic to the guinea pig cochlea.

Assessment of communicating systems on the basis of an ecological conceptual framework.

A conceptual framework for auditory communication was constructed based on biological ecosystem theories. The framework was used to analyse and conceptualize the assessment of auditory communication and rehabilitation. Two different strategies for assessment are presented: analytical and holistic. It is observed that the application of the ecological concept preferendum (optimum) calls for both qualitative and quantitative assessment methods. The role of situation, the composition of the communicative system and the perspectives of the different actors were cornerstones of the analytical assessment. The holistic assessment can be approached in terms of matters such as satisfaction (ecological balance) and fatigue. Description of the communicative mass in the present framework, analogous to biomass in biological systems, was identified as a suitable endpoint of holistic assessment, formed from the total knowledge and positive emotions generated in the system. Communicative mass was described in three dimensions: the number of participants in the communicative system, time in communication, and flow of knowledge and emotion. The operationalization and application of this concept are discussed.

Exploring the perceived world of the deaf-blind: on the development of an instrument.

In the present interview study on a sample of 13 deaf-blind participants (eight Usher patients and five with other diagnoses), all but one with some remaining visual function and all but two with a pure-tone average (PTA) exceeding 100 dB HL, an instrument was developed to assess discovery and localization abilities (DILO), compensatory use of sensory information, emotional and cognitive aspects of communication, and the preferred use of technical aids. Both qualitative and quantitative data were collected, and it was found that (1) the importance of early discovery of events and persons is rated high, (2) vision ranks higher than other sensory information, and airflow, smell and residual hearing come next in the perceptual world of this sample, (3) cognitive aspects of communication correlate with the importance of discovery and localization, and (4) technical aids dominated by vision and vibratory senses are preferred. It is concluded that even a small remaining visual function could be of significant importance in rehabilitation. Finally, in the deaf-blind group of subjects with some remaining visual function, utilization of remaining vision was felt to be more important than utilization of other sensory modalities.