Evaluation of speech production of the hearing impaired: some benefits of forced-choice testing.

The speech production performance of 16 hearing-impaired subjects (thresholds 82-110 dB HL) was measured using both experienced and inexperienced listeners. Four types of measure were obtained: score on a forced-choice test requiring the production of eight segmental contrasts, recognition probability for phonemes produced in consonant-vowel-consonant (CVC) words, recognition probability for CVC words produced in a simple carrier phrase, and recognition probability for words produced in sentence context. The experienced listeners gave higher scores than did the inexperienced listeners, but the magnitude of the effect decreased with decreasing linguistic redundancy in the test material, falling to only 1.3 percentage points for the forced-choice test. The pattern of performance across the eight contrasts of the forced-choice test changed significantly from subject to subject. Performance on the contrast test accounted for 70% of the variance in the scores on the sentence test. The results demonstrate that forced-choice tests can be used to provide speech production measures that are virtually independent of listener experience, that provide analytic detail about an individual's production of phonetic contrasts, and that are reasonably predictive of the intelligibility of speech produced in more natural communicative settings.