Speech and Hearing Sciences ETDs

Publication Date

7-24-1973

Abstract

The effect of duty cycle, or the percentage of time a signal is presented, upon the perceived loudness of a pulsed tone was studied utilizing an alternate monaural loudness balance technique. The single ear was employed in an attempt to eliminate any possible artifacts of binaural interaction upon the perceived loudness of pulsed signals.

The factors under investigation included: the difference in duty cycle between a fixed-intensity reference signal and a variable-intensity comparison signal; the use of a relatively high versus a relatively low duty cycle reference signal; and the effect of time after commencement of the loudness balances. Differences in duty cycle between the two tones were set by the experimenter to equal 0, 30, 60 and 80%. Ten normal hearing individuals adjusted the intensity of the 4000-Hz comparison tone to equal the loudness of the fixed-intensity 1000-Hz reference tone over 4-minute trials. The alternate monaural loudness balance technique was employed via the Bekesy audiometer. This pursuit auditory loudness tracking task was a combination of the psychophysical method of limits and the method of adjustment.

The results of the study indicated that loudness, in part, was affected by the signals' duty cycles. During loudness balances with a relatively high duty cycle, the intensity of the comparison signal was continually made more intense as the reference signal was increased in duty cycle, indicating an increased perceived loudness of the refer­ence signal. However, during the loudness balances in which a relatively low duty cycle reference signal was utilized, an opposite duty cycle-loudness effect occurred. As the duty cycle of the comparison signal was increased, from trial to trial, it was continually made more intense in order to maintain equal loudness with the low duty cycle reference. A significant difference between the three disparate duty cycle conditions was noted within the two experimental reference signal conditions. During the entire experiment, a significant linear growth of response was observed.

The experimental results are in agreement with data from past research concerning the relationship of duty cycle to loudness in which a loudness-memory method and an alternate binaural loudness balance task were utilized.

Degree Name

Speech-Language Pathology

Level of Degree

Masters

Department Name

Speech and Hearing Sciences

First Committee Member (Chair)

Karl William Hatter

Second Committee Member

Max Edgar McClellan

Third Committee Member

William John Ryan

Fourth Committee Member

Richard Baxter Hood

Language

English

Document Type

Thesis

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