Biomedical subjects

J M Besing

Publications and source records attributed to J M Besing.

4 recordsLinked to original sources

PubMed2000

Binaural gap duration discrimination in listeners with impaired hearing and normal hearing.

OBJECTIVE: This study was designed to measure the ability of listeners with and without sensorineural hearing loss to discriminate silent gaps between noise band markers of different frequencies presented in an anechoic and a reverberant listening environment. DESIGN: A two-interval, two-alternative, forced-choice paradigm was used to measure gap discrimination ability for six listeners with normal-hearing and six listeners with sensorineural hearing impairment. Marker stimuli were narrow bands of noise centered at frequencies from 500 to 7000 Hz. The center frequency of the leading marker was held constant at 2000 Hz and the center frequency of the trailing marker was varied randomly across runs. Stimuli were presented in two virtual listening environments (anechoic and reverberant). The listeners' task was to indicate which interval contained the marker pair separated by the larger silent gap. Gap discrimination was measured as a function of the center frequency of the trailing marker and as a function of listening environment. RESULTS: Gap discrimination thresholds (msec) varied as a function of the center frequency of the trailing marker. As the trailing marker frequency increased above and decreased below the leading marker frequency (2000 Hz), gap thresholds increased significantly. Hearing loss and listening environment did not have a significant effect on gap discrimination thresholds. Analysis of the gap discrimination functions revealed significantly steeper slopes for trailing marker frequencies below 2000 Hz than for trailing marker frequencies above 2000 Hz. A possible age effect was observed in the data and significant correlations were found between age and function slopes for several conditions. CONCLUSIONS: Gap discrimination becomes more difficult as the frequency disparity between leading and trailing noise bands increases. This pattern of results occurs independent of hearing loss but may be influenced by listener age.

Adult↗

PubMed1996

A procedure for testing speech intelligibility in a virtual listening environment.

OBJECTIVE: The development of a test of virtual speech intelligibility in noise that enables assessment in typical, everyday listening situations. To eliminate extraneous confounding factors, digital signal processing was incorporated to simulate listening environments and source locations and allow presentation of stimuli via earphones. DESIGN: Source-to-eardrum transfer functions measured on KEMAR for various source locations in anechoic and reverberant environments were used to process monosyllabic words and speech-spectrum noise. Speech intelligibility was measured for three speech and noise configurations in two environments using an adaptive procedure to determine the signal-to-noise (S/N) ratio for 50% intelligibility. RESULTS: Normal-hearing listeners achieved 50% intelligibility of monosyllabic words at significantly lower S/N ratios in a virtual anechoic environment than in a virtual reverberant environment. Speech intelligibility improved significantly in both environments when the speech and noise sources were separated, but the intelligibility gain in the anechoic environment was four times larger than in the reverberant environment. CONCLUSIONS: This test is easy to administer and score, and it provides a means for measuring: 1) the effects of separating speech and noise sources and 2) the effects of reverberation on speech intelligibility in noise while eliminating confounding factors such as calibration.

Hearing↗

PubMed1995

A test of virtual auditory localization.

OBJECTIVE: The purpose of this study was to evaluate a test of virtual auditory localization including assessment of its ease of administration and its sensitivity to differences in binaural performance in children and adults. This test eliminates many potential problems inherent in any free-field localization test such as calibration problems, problems replicating source and listener locations, and issues associated with head movements. DESIGN: Binaural performance was measured using the virtual localization test and a simple binaural detection task, the masking-level difference (MLD), for three groups of subjects: adults, children with a negative history of otitis media, and children with a positive history of otitis media. There were five subjects in each group. The adults were all student volunteers; the children were recruited first and subsequently placed into groups based on their medical histories obtained from their physicians and parental reports. RESULTS: Results indicate that this test of virtual auditory localization is useful for measuring binaural performance in children and adults and is sensitive to differences in binaural processing. Performance of the adults and children with a negative history of otitis media was comparable on both of the binaural tests, and on the binaural detection task, was similar to that reported in the literature for normal-hearing listeners; but the children with a positive history of otitis media performed more poorly on both tests. CONCLUSIONS: The results of this study indicate that the virtual localization test described here is easy to administer to children and adults. The signal processing techniques used in this virtual auditory localization test lend themselves to straightforward comparisons across different laboratories and clinics and make this test a potentially useful clinical tool. The development of such a clinical test is currently under study.

Adult↗

PubMed1992

Effects of roving level variation on monaural detection with a contralateral cue.

Monaural detection with a contralateral cue (MDCC) was measured with and without a 20-dB overall roving level to determine the contribution of loudness to performance on this task. Psychometric functions were obtained for three normal-hearing subjects as a function of the signal-to-noise ratio for pure-tone and 1/3-oct noiseband signals at 500 and 4000 Hz with a wideband noise masker. At 4000 Hz, the roving level degrades performance for the narrow-band noise signal by about 5.3 dB. In addition, the presence of the contralateral cue degrades performance for both the pure-tone and narrow-band noise signals at 4000 Hz by 3 to 6 dB. At 500 Hz, however, performance is not affected by the roving level, and is improved by 3 to 6 dB by the contralateral cue. These results indicate that loudness is being used as a cue only for detection of the 4000-Hz narrow-band noise.

Acoustics↗