Development of Novel Speech Stimuli With Phonetic Coverage and Phonemic Balance.

Purpose: Gurevich and Kim (2022) call for new speech materials that provide not only phonemic but also allophonic coverage so that production and perception of consonants can be examined as a function of their positional contexts. The purpose of this work was to construct such materials. Method: A total of 466 allowable contexts for the 24 English consonants were determined by considering positional contexts in terms of word and syllable positions, lexical stress, and proximity to other phonemes. These contexts were filled using 308 unique tokens composed of frequent content words ensuring both phonemic and allophonic coverages. In addition, the words were combined into 37 declarative and interrogative phrases to incorporate prosodic elements of speech. Twenty healthy adults were recorded reading these phrases to assess time and effort required for the task. Results: The newly constructed speech materials achieved high-overall phonetic coverage at 83.05% of all allowable English contexts, including coverage of consonant categories and positional contexts of particular importance for clinical and research purposes. Moreover, these materials attained the balance of consonant frequencies in typical spoken English. This was achieved with 37 phrases that take an average of 3 min, 6 s to read at an average of 5.02 s per phrase. Conclusions: Compared with the commonly used standard reading passages examined in Gurevich and Kim (2022), the newly constructed materials provide significantly superior phonetic coverage, including important linguistic features known to affect production and perception of consonants. The new materials are therefore well suited for eliciting speech representative of General American English for investigating consonant production and perception.