Influence of auditory fatigue on masked speech intelligibility

Intelligibility of PB word lists embedded in simultaneous masking noise was evaluated before and after fatiguing-noise exposure. Intelligibility was determined by observing the number of words correctly repeated during a shadowing task. Both the speech signal and the masking noise were filtered to a 2825-3185 Hz band. Masking-noise levels were varied from 0- 90-dB SL. Fatique was produced by a 1500-3000-Hz octave band of noise at 115 dB (re 20 muPa) presented continuously for 5 min. The results of three experiments indicated that speech intelligibility was reduced when the speech was presented against a background of silence but that the fatiguing-noise exposure had no effect on intelligibility when the speech was made more intense and embedded in masking noise of 40-90-dB SL. These observations are interpreted by considering the recruitment produced by fatique and masking noise.