ACOUSTIC-PHONETIC CONTEXT CONSIDERATIONS FOR SPEECH RECOGNITION TESTING OF HEARING-IMPAIRED LISTENERS

Objective: To test for differences in the identification of consonants in carrier sentences versus in VCVs extracted from the sentences, as a function of listeners' hearing-loss categories: moderate, severe, pr ofound. To examine whether pauses inserted in the sentences will facil itate identification of the consonants. Design: Voiced stops and frica tives were identified by 11 listeners with moderate hearing losses and by 7 Listeners with severe losses (between subjects design) for the c onditions of consonants in sentences and in VCVs extracted from the se ntences (repeated measures). Nine of these Listeners also identified t he consonants in the sentences with pauses. Six normal-hearing listene rs were tested for the consonants in the extracted VCVs and the senten ces. Voiceless stops and fricatives were identified by 4 listeners wit h profound losses, 18 with severe losses, and 8 with moderate losses ( between subjects) for the conditions of extracted VCVs and the sentenc es (repeated measures). AU listeners were selected on the basis of the ir hearing levels. Results: The listeners with moderate to severe hear ing loss identified the voiced stops and fricatives more poorly when t he syllables were in the carrier sentences than when extracted. Insert ion of the pauses in the sentence did not improve performance signific antly. The normal hearing listeners showed no differences in consonant identification between the two conditions, perhaps due to ''ceiling e ffects.'' The voiceless stops and fricatives were also identified more poorly when in the extracted VCVs than in the carrier sentences by ot her listeners with moderate to profound hearing loss. Conclusions: Lis teners with moderate or greater hearing loss can show poorer identific ation of consonants that are embedded midway in carrier sentences than when the acoustically identical consonants are in VCVs extracted from the sentences. The performance reduction for the consonants in senten ces is not relieved from insertion of brief artificial pauses in the s entences. Further research is needed determine whether hearing-impaire d listeners' identification of consonants in target words of clinical word recognition tests is facilitated when the words are extracted fro m carrier phrases.