Speech-Reception Threshold in a Fluctuating Background Sound and its Possible Relation to Temporal Auditory Resolution

Abstract

The speech-reception threshold (SRT) in noise is a frequently encountered limitation in everyday aural communication, especially for hearing-impaired listeners. The SRT for sentences can be described with a simple signal-to-noise ratio model (Plomp, 1987) containing two parameters related to hearing loss: ‘A’ for attenuation and ‘D’ for distortion. Hearing loss for speech in noise is represented by the parameter D and hearing loss for speech in quiet by the sum of A and D, both in decibels. In normal-hearing listeners the SRT for short meaningful sentences (50% correct) in noise is reached about -5dB signal-to-noise ratio. At threshold, hearing-impaired listeners need a better signal-to-noise ratio, up to 10 dB, depending on the kind of hearing loss (D, 10dB). Although hearing loss for speech in noise may seem moderate in terms of decibels, it should be noted that in critical conditions 1 dB increase in signal-to-noise ratio gives an 18% higher intelligibility score for sentences (Duquesnoy, 1983). As a result, in such conditions, speech that is intelligible to normal-hearing listeners may be completely unintelligible to hearing-impaired listeners.