Speech perception enhanced by noise in listeners with normal hearing

Most often, noise is considered a major factor in the degradation of listening conditions. Recently, however, there is increasing evidence suggesting that the addition of low-intensity noise can improve signal detection in non-linear systems. While this phenomenon has been described in physical systems, very little has been documented regarding its functional significance in the human sensory system in general, and in the auditory system in particular. The purpose of the present study was to investigate the benefit of adding noise to the recognition of speech already embedded in background noise. Participants included 27 adults with normal hearing, between 20 and 30 years of age. Speech stimuli were consonant-vowel-consonant monosyllabic words. Babble noise (BN) was added until word recognition dropped to threshold levels (below 50%). Additional low-level noise (LLN) was added to the words + BN in an alternating design (i.e., words + BN + LLN, words + BN, etc.). For each participant, word recognition scores were based on 25 words in BN and 25 words in BN + LLN. The number of words was distributed unequally across the conditions. The results show that for 63% of the participants, adding LLN enhanced scores significantly by 4-32%. Of these participants, 70% showed that adding LLN to speech-in-noise improved performance by more than 12%. Additional noise seems to help when word recognition score in BN was lower than 50%. These results provide first-time evidence for the benefit of low-intensity noise in order to enhance speech-in-noise in hearing listeners.