Comparative Bekesy typing with broad and modulated narrow-band noise.

Abstract

This study explored the effectiveness of modulated narrow-band noise as a masking source for sweep-frequency Bekesy audiometry. Five sophisticated normal-hearing subjects traced Bekesy audiometry thresholds for pulsed and continuous tone with no masking and under three conditions of contralateral masking: (1) white noise, (2) modulated narrow-band noise with a constant band-width of ±150 Hz, and (3) modulated narrow-band noise with a band-width of ±300 Hz. Results indicated that the continuous tone tracing obtained under the second condition separated from the pulsed tracing supportive of a Type II tracing. With the third condition, pulsed-continuous differences were somewhat smaller. Under the first condition, the difference between pulsed and continuous tracings was not apparent. When two unsophisticated subjects were tested with the modified band-width noise, results indicated extreme variation between pulsed and continuous tracings. We concluded that the masking effect of a constant band-width modulated narrow-band noise is about the same as that of white noise for a pulsed tone tracing. However, the use of a modulated narrow-band noise masking source may cause false Type II Bekesy audiograms due to the greater masking effect on a continuous tone threshold.