The effect of noise‐induced hearing loss on speech intelligibility in noise and its implications for noise damage risk criteria

Abstract

Speech reception thresholds for sentences presented both in quiet and in background noise, and tone audiograms were measured for 14 normal ears (7 subjects) and 44 ears (22 subjects) with noise‐induced hearing loss (NIHL). For the 22 subjects with NIHL maximum hearing loss was found in the 4–6 kHz region at 40 to 90 dB (losses exceeded by 90% and 10%, respectively). Hearing loss for speech presented in quiet was only 1.8 to 13.4 dB. For speech in noise hearing loss was 1.2 to 7 dB which means that the subjects with NIHL needed a 1.2 to 7 dB higher speech‐to‐noise ratio than normals to understand the sentences equally well. A 1‐dB decrease in speech‐to‐noise ratio implies a decrease in sentence intelligibility of 15% to 20%. There was virtually no correlation between the hearing loss for speech presented in quiet and the loss for speech presented in background noise. Speech thresholds found in quiet showed the highest correlation with losses in the tone audiogram at 500 Hz whereas speech thresholds in nois...