Intelligibility of speech in noise at high presentation levels: effects of hearing loss and frequency region.
These experiments examined how high presentation levels influence speech recognition for high- and low-frequency stimuli in noise. Normally hearing (NH) and hearing-impaired (HI) listeners were tested. In Experiment 1, high- and low-frequency bandwidths yielding 70%-correct word recognition in quiet were determined at levels associated with broadband speech at 75 dB SPL. In Experiment 2, broadband and band-limited sentences (based on passbands measured in Experiment 1) were presented at this level in speech-shaped noise filtered to the same frequency bandwidths as targets. Noise levels were adjusted to produce approximately 30%-correct word recognition. Frequency bandwidths and signal-to-noise ratios supporting criterion performance in Experiment 2 were tested at 75, 87.5, and 100 dB SPL in Experiment 3. Performance tended to decrease as levels increased. For NH listeners, this "rollover" effect was greater for high-frequency and broadband materials than for low-frequency stimuli. For HI listeners, the 75- to 87.5-dB increase improved signal audibility for high-frequency stimuli and rollover was not observed. However, the 87.5- to 100-dB increase produced qualitatively similar results for both groups: scores decreased most for high-frequency stimuli and least for low-frequency materials. Predictions of speech intelligibility by quantitative methods such as the Speech Intelligibility Index may be improved if rollover effects are modeled as frequency dependent.
Summers
Van
V
Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA. walter.summers@na.amedd.army.mil
Cord
Mary T
MT
D000368:Aged; D001309:Auditory Threshold; D005260:Female; D006309:Hearing / Q000502:physiology*; D034381:Hearing Loss / Q000503:physiopathology*; D006316:Hearing Loss, High-Frequency / Q000503:physiopathology; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology; D006801:Humans; D007802:Language; D008875:Middle Aged; D009622:Noise; D013060:Speech; D013065:Speech Intelligibility; D013067:Speech Perception; D049250:Speech Recognition Software