The effect of noise-induced hearing loss on speech intelligibility in quiet and in noise

Abstract

Following a pilot study (Smoorenburg et al., Scand. Audiol., Suppl. 16, 123–133) based on 44 ears (22 subjects) with noise-induced hearing loss (NIHL) we conducted a study based on 400 ears with different degrees of NIHL. The study included speech reception thresholds for sentences presented in quiet and in noise, tone audiograms measured in quiet and against a low-frequency background noise, and self-rating of the hearing handicap according to the Social Hearing Handicap Index. The results show 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 show the highest correlation with losses in the tone audiogram at 0.5 and 1 kHz, whereas speech thresholds in noise show the highest correlation with the losses at 2–4 kHz. The speech thresholds will be compared with predictions from the audiogram using the Articulation Index procedure and with the audiograms measured against a low-frequency background noise. Only those questions in the Social Hearing Handicap questionnaire that refer directly to practical situations show a correlation with the speech thresholds. The results for speech perception in noise show that the AAOO fence of 25-dB average hearing loss across 1/2, 1, and 2 kHz implies a severe auditory handicap. The fence should be set at a lower level and it should include audiometric frequencies.