The Carhart Memorial Lecture, American Auditory Society, Salt Lake City, Utah 1996. Phoneme and word recognition for words in isolation and in sentences.

Objective: To evaluate relations among scores for phonemes, words in isolation, and words in sentences for listeners with normal hearing and for listeners with sensorineural hearing loss.

Design: Ten-word lists of consonant-vowel-consonant monosyllables with each list utilizing the same 10 vowels and 20 consonants (Boothroyd, 1968) were devised and recorded. These words also were incorporated into contextually correct sentences and recorded by the same talker. The materials were presented in quiet to 36 listeners with normal hearing and to 876 listeners (1260 ears) with sensorineural hearing loss. Formulae derived by Boothroyd and Nittrouer (1988) to relate scores for phonemes, words, and sentences were applied to the data.

Results: Phoneme scoring yielded scores that were on the order of 20% higher than scores for whole words heard in isolation, and scores for words in sentences were about 20% higher than when the same words were heard singly. Relations among scores for phonemes, words in isolation, and words in sentences were very similar to those observed by Boothroyd and Nittrouer (1988). The constants derived from application of their formulae to our data were very similar to the constants Boothroyd and Nittrouer obtained for a different set of materials presented against a noise background to listeners with normal hearing. Further, the constants were similar for our group of listeners with normal hearing and our large sample of listeners with sensorineural hearing loss.

Conclusions: 1) These findings support Bilger's (1984) unifying assumptions that speech recognition is a single construct; therefore, scores on all speech recognition tests must be related and scores on one speech recognition test should be predictive of scores on other tests. 2) Advantages of phoneme scoring include: A) It increases the sample size of scored items for a given list of words, thereby reducing variability in test results. B) Statistical equivalence of phoneme scores for the same 30 phonemes in each of two isophonemic word lists can be evaluated quickly and easily by applying the binomial distribution model to the scores (Thornton & Raffin, 1978). C) Phoneme scores are reasonably accurate predictors of recognition of words in the contextually correct but generally low probability sentences used in this study.