Intelligibility of intervocalic consonants in noise

The intelligibility of speech, in terms of sentence intelligibility, at low levels of noise is almost perfect, although some redundancy may already have been lost, which could result in a reduced listening comfort. In order to study this in conditions representative of normal communication, we used the intelligibility of consonants in vowel-consonant-vowel segments excerpted from conversational speech as a sensitive measure. The level of the noise while listening was systematically varied. The consonant intelligibility score, averaged over consonants (18), speakers (5), and listeners (10), was about 70% correct in a quiet condition, and started to degrade at a signal-to-noise ratio of 10 to 7 dB. Results furthermore show that when the speaker himself is also in the noise he does not just talk louder but also more intelligible. However, providing the listener with a visual image of the speaker does not improve intelligibility.