Effects of Intensity Level on Threshold Shifts Produced by Pulsed and Continuous Maskers

Abstract

The effect of pulsed versus continuous maskers as a function of intensity level was investigated. The test signals were pulsed or continuous pure tones at the frequencies of 250, 1000, and 4000 cps. A wide-band random noise was presented either to the test ear (monotic) or the contralateral ear (dichotic) of four trained observers at intensity levels of 15, 30, 45, 60, and 75 dB SPL. Three methods of presentation included: (1) pulsed tone and pulsed masker (simultaneous); (2) pulsed tone and continuous masker; and (3) continuous tone and continuous masker. The results from the monotic and dichotic conditions showed that (a) for a pulsed tone signal the pulsed masker was more effective even at the low intensity levels, and (b) a continuous masker produced greater masking in the high frequencies if the tone signal was also continuous. During the dichotic condition, increased threshold shifts were observed as the intensity level of the noise increased. This result was most evident for the pulsed-pulsed and continuous-continuous presentations. The differential effects of frequency were considered in the interpretation of the results. [This work was supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]