Speechreading ability was investigated among hearing aid users with different time of onset and different degree of hearing loss. Audio-visual and visual-only performance were assessed. One group of subjects had been hearing-impaired for a large part of their lives, and the impairments appeared early in life. The other group of subjects had been impaired for a fewer number of years, and the impairments appeared later in life. Differences between the groups were obtained. There was no significant difference on the audio-visual test between the groups in spite of the fact that the early onset group scored very poorly auditorily. However, the early-onset group performed significantly better on the visual test. It was concluded that the visual information constituted the dominant coding strategy for the early onset group. An interpretation chiefly in terms of early onset may be the most appropriate, since dB loss variations as such are not related to speechreading skill.
Unilaterally severely hearing impaired persons, who may experience substantial communication problems in situations of high acoustic demands, would in theory benefit from contralateral routing of signals (CROS). However, reports of failure because of too much disturbing noise and distortion have been common. The reason for a low success rate in CROS, though, is an inappropriate fitting procedure, due to lack of understanding of the basic principle of CROS among both patients and audiologists. The precondition for success in CROS is an accurate description of the individual hearing deficit and a correctly balanced adjustment of the CROS aid through testing under sound field conditions, combined with a comprehensive follow-up.
The effect of different treatment programs in audiological rehabilitation was evaluated. The speech intensity at which subjects with high frequency hearing loss correctly perceived 50% of the key words in sentences was measured in quiet and in noise, with and without a hearing aid and with and without simultaneous speech reading. No statistically significant difference in audiovisual speech perception ability was found between subjects receiving no training, subjects receiving a 6-hour information course, or a 3-week intensive training in auditory and audiovisual speech perception. Large differences in the degree of hearing aid usage was found, however, between the three treatment groups. An analysis of the individual results from the speech test used showed that some subjects improved with the use of a hearing aid, whilst others deteriorated. The degree of hearing aid usage was considerably influenced by the measured effect of the hearing aid treatment. Our findings stress the need for an objective test by which to measure the effect of hearing aid fitting. As a result of the reported study a series of experiments have been started with the aim of obtaining a better understanding of the audiovisual speech perception process. These studies are based on an information-processing model for speech perception. Particular attention is devoted to the importance of the prosodic information in the auditory speech signal.
In order to select hearing aids with a highly predictable real ear gain, in situ gain and compliance through the individual ear mould were measured on 8 normal-hearing subjects. The latter were chosen in order to reduce gain variation caused by various pathological conditions of the ear. All behind-the-ear aids commonly used in Sweden and one in-the-ear aid were studied. One sample of each hearing aid type was tested and the subjects had identical ear moulds. Hence, the variables were hearing aid type and subject. The study showed wide intra-subject coupler-related real ear gain variation (30 dB). Most of the aids showed a distinct correlation between coupler-related overall gain, and mould compliance. Some of the aids gave more uniform real ear gain, i.e. low interaction between subject and frequency-dependent gain. These results are elucidated by measuring the aid's acoustic output impedance.
The most common complaint among individuals with hearing impairment is the inability to follow a conversation when several people are talking simultaneously, a noisy listening situation which is completely different from the quiet surrounding of the conventional pure tone audiometry used as basis for the hearing aid settings. The purpose of this report was to present important characteristics of the BeneFit Method (BFM), a procedure that fits the hearing aid under simulated conditions of competing speech and also a clinical pilot evaluation study comparing the BFM to the NAL-R recommendations and also to the Logic procedure, a GN resound proprietary fitting algorithm representing a modern digital hearing aid fitting procedure. Speech recognition scores in noise (SRSN) using monosyllabic words presented under different background noise levels were evaluated on 21 randomly selected subjects with hearing impairment. The subjects were fitted with the same type of hearing aid Danalogic 163D according to the BFM procedure as well as the logic procedure, the latter developed and recommended by the manufacturer. A comparison of the SRSN when using the subjects' current hearing aid fitted according to the NAL-R procedure was also made. Only the BFM procedure provided a significant SRSN improvement compared to the unaided condition (P< 0.01) in a signal/speech-noise level of 75/65 dB corresponding to a normal cocktail party condition. Moreover, patients performed significantly higher SRSN when fitted according to the BFM, than when fitted according the Logic or NAL-R procedures. The BFM procedure, which is based on individual and functional detection of hearing thresholds in noise levels corresponding to a cocktail party condition, can improve SRSN significantly. Hearing aids should be fitted under conditions similar to those when the hearing disability is perceived the most, i.e, in an environment with background noise.
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