Effects of intensity on speech recognition in high- and low-frequency bands.
OBJECTIVE
This study investigated the intensive effects of a low-frequency (200 to 400 Hz) and a high-frequency (1000 to 5000 Hz) band of speech presented jointly and in isolation.


METHODS
Each band was presented at a reference intensity level equivalent to the average normal conversational level. To investigate intensive effects, the low-frequency band was presented at 20 dB and 36 dB, and the high-frequency band at 20 dB above the reference level. Each band was presented at a fixed signal-to-noise ratio. Subjects were four normal-hearing adult females. The AI was used to predict performances and to determine audibility of each band.


RESULTS
The best performance occurred for a joint band presentation with each band at the reference level. Increasing intensity of one band by 20 dB, for joint band conditions, did not significantly affect performance. However, increasing the low-frequency band by 36 dB or both bands by 20 dB resulted in a significant decrease in performance.


CONCLUSIONS
Reduced performance with the low-frequency band at 36 dB and the high-frequency band at the reference level is attributed primarily to upward spread of masking by speech. Performance decrements for other joint band conditions are attributed to combined effects of high intensity.
Goshorn
E L
EL
Louisiana Tech University, Department of Speech, Ruston.
Studebaker
G A
GA
D000328:Adult; D005260:Female; D006801:Humans; D013069:Speech Reception Threshold Test; D013647:Task Performance and Analysis