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Biomedical subjects

S M McFadden

Publications and source records attributed to S M McFadden.

5 recordsLinked to original sources
PubMed2001

The relative impact of generic head-related transfer functions on auditory speech thresholds: implications for the design of three-dimensional audio displays.

BACKGROUND: Auditory speech thresholds were measured in this study. METHODS: Subjects were required to discriminate a female voice recording of three-digit numbers in the presence of diotic speech babble. The voice stimulus was spatialized at 11 static azimuth positions on the horizontal plane using three different head-related transfer functions (HRTFs) measured on individuals who did not participate in this study. The diotic presentation of the voice stimulus served as the control condition. RESULTS: The results showed that two of the HRTFS performed similarly and had significantly lower auditory speech thresholds than the third HRTF. All three HRTFs yielded significantly lower auditory speech thresholds compared with the diotic presentation of the voice stimulus, with the largest difference at 60 degrees azimuth. CONCLUSION: The practical implications of these results suggest that lower headphone levels of the communication system in military aircraft can be achieved without sacrificing intelligibility, thereby lessening the risk of hearing loss.

Acoustics↗
PubMed2000

Release from masking in virtual auditory space during sustained positive acceleration.

BACKGROUND: The use of a three-dimensional (3-D) auditory display to significantly lower subject detection level while maintaining comprehension under sustained positive G-stress was explored in this study. METHODS: Auditory threshold levels were measured for detecting a band limited pulsed signal in the presence of a broadband diotic masker at both + 1 Gz (rest position) and under sustained +3 Gz. The pulsed signal was presented diotically and was spatialized at one of four static azimuth positions on the horizontal plane. RESULTS: Results showed that auditory thresholds were not significantly affected by sustained +3 Gz stress. Compared with a diotic presentation, subjects reached an average of 6.8 dB lower auditory threshold at +1 Gz and under sustained +3 Gz when the pulsed signal was spatialized at a static position of 90 degrees azimuth on the horizontal plane. CONCLUSION: The implication of these results and suggestions for further research are discussed.

Adult↗
PubMed1994

A comparison of two contrast sensitivity tests and their usefulness as a screener for aircrew.

This study investigated the usefulness of two contrast sensitivity tests for aircrew selection. The first, carried out on a Nicolet CS 2000 Contrast Sensitivity System, used a two-interval forced choice methodology (2IFC) and an adaptive procedure. The second was the VISTECH VCTS 6500 Test System. The contrast sensitivity of 50 aircrew candidates and 23 subjects was measured. Two independent measures were taken on the 23 subjects to get an estimate of test-retest variability. Mean contrast sensitivity with the 2IFC methodology was significantly higher at 1.5, 3, and 6 cpd than with the VCTS 6500. The variance in the scores of the aircrew population on the VCTS 6500 was almost identical to the within-subject variance based on the test-retest data. Thus, any differences in contrast sensitivity across the aircrew population could not be picked up by the VCTS 6500. The variance in the scores of the aircrew candidates with the 2IFC method was larger than the within-subject variance, but the evidence suggested that most of this variation was due to factors other than differences in contrast sensitivity across the aircrew population. It was concluded that neither test was suitable for screening the contrast sensitivity of Canadian Forces aircrew candidates, but that both tests could be useful for testing more heterogeneous populations. Moreover, since the shape of the contrast sensitivity function varies across tests, absolute scores on different tests are not comparable.

Adolescent↗
PubMedDate not supplied

Providing for the severely handicapped: a case for competency-based preparation of occupational therapists.

Recent court decisions that mandate the development of new instructional alternatives for severely handicapped children will have significant implications for occupational therapists. Focusing on such issues as mainstreaming, accountability, and certification standards, this paper places in perspective the problems and trends that have led to this new challenge. It also provides suggestions for the development and disposition of training programs that can ultimately result in more appropriate programming for the handicapped children in the new population to be served in the public schools. Illustrated with examples of competency components and behavioral objectives, competency-based occupational therapy preparation programs are emphasized.

Child↗