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Biomedical subjects

G D Causey

Publications and source records attributed to G D Causey.

7 recordsLinked to original sources
PubMed1978

Measurement of attack-release times in compression hearing aids.

A system for measurement of attack-release times in hearing aids with automatic-gain-control circuitry is described, with a view toward implementing that portion of the ANSI S3.22-1976 Standard in which parameters for these measurements are specified. Signal generation is accomplished by using a phased-array loudspeaker arrangement designed to produce transient-free pulsed acoustic sinusoids. Output waveforms are captured by a commercial transient recorder, and are displayed in either an oscilloscopic or graphic mode. A specific means of calculating attack and release times is recommended whereby variously shaped output waveforms are amenable to the basic protocol outlined in the ANSI Standard.

Acoustics↗
PubMedDate not supplied

The influence of hearing aid nonlinear distortion on two auditory tasks.

A study is reported which examines the influence of hearing aid nonlinear distortion on multitone pitch perception. Normal-hearing subjects produced results indicating that hearing aid-generated harmonic and intermodulation components did significantly affect pitch judgments. Substantial differences in the amount of distortion between the two test aids was not, however, a critical factor. A follow-up study using closed-set intelligibility materials in noise further confirmed that relatively large measurable differences in nonlinear distortion between hearing aids do not seem to have the clinical significance which is often presumed.

Adult↗
PubMedDate not supplied

The relative importance of recovery time in compression hearing aids.

Recovery time (RT) in compression hearing aids was studied using six aids of identical characteristics except for factory-modified RT. Recordings of CID W-22 lists were made through the aids and played to normally hearing and otopathologic (sensorineural) subjects. Speech intelligibility was measurably influenced by RT variation with attack time held constant (10 ms). The effect was much more pronounced with the normal than with the hearing-impaired listeners, a phenomenon not unexpected when testing such a subtle feature in a low-fidelity transmission system. When the RTs of the aids were respecified according to a proposed standard (IEC) the data suggested that RTs for English in the vicinity of 90 ms may be most desirable. Additional work is required using more complex stimuli and background noise.

Auditory Perception↗
PubMedDate not supplied

Nonlinear distortion in hearing aids: the need for reevaluation of measurement philosophy and technique.

Conventional pure-tone tests of harmonic distortion are of dubious sufficiency in expressing the nonlinear distortion (NLD) characteristics of hearing aids. This paper reviews the strategies and problems of intermodulation distortion. Spearman rank order correlations for a group of hearing aids varied widely as a result of changes in the selected frequency and/or level of input signal. Also, the reference criteria for expressing distortion was observed to contribute to the inconsistency of rank order impression. A technique is described which incorporated synthetic vowels as test signals. Hearing aid outputs were studied on a spectrum analyzer for evidence of NLD. It is argued that efforts should be directed at devising tests for hearing aids which are directed at comprehensive NLD including both harmonic distortion and intermodulation distortion.

Evaluation Studies as Topic↗