Children with dysarthria due to cerebral palsy (CP) present with decreased vowel space area and reduced word intelligibility. Although a robust relationship exists between vowel space and word intelligibility, little is known about the intelligibility of vowels in this population. This exploratory study investigated the intelligibility of American English (AE) vowels produced by children with dysarthria and typically developing children (TD). Three CP and five TD repeated words with contrastive vowels /i-ɪ/, /æ-ɛ/, /ɑ-ʌ/, /o-u/ produced by a native AE adult. Adult listeners transcribed the utterances orthographically and rated their ease of understanding. Overall, CP presented with less-intelligible vowels than TD. For CP, a trend was found with the lowest intelligibility for /ɑ/ (CP = 7%, TD = 66%), /ɪ/ (CP = 30%, TD = 82%), and /ʌ/ (CP = 38%, TD = 99%), and more heterogeneous vowel confusions; however, intelligibility differences between vowels did not reach statistical significance. Clinical implications include that, unless further studies show vowel-specific effects, treatment targeting the entire vowel system may be warranted for increasing intelligibility.

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Clear speech, an intelligibility-enhancing manner of speech production, has been shown to increase the transmission of information to various listener groups when uttered in the speaker’s native language. When clear speech is used in a non-native language, it is not evident whether this mode will also improve intelligibility. The present study examined the accuracy with which adult monolingual native American English (AE) listeners identified Spanish-accented vowels produced in conversational and clear speech modes. Consonant-vowel-consonant (CVC) words were presented in the carrier sentence “Touch the CVC please,” containing the AE vowels /æ, ʌ, ɑ, ε, i, ɪ/. The sentences were produced by a native speaker of AE and by a native speaker of Spanish judged as moderately accented by the AE listeners. Five pairs of photographs (cap-cup, map-mop, nut-knot; ship-sheep, pot-pet), representing the vowel pairs /æ-ʌ/, /æ-ɑ/, /ʌ-ɑ/, /ɪ-i/, /ɑ-ε/ were presented visually on a touch screen in a two-alternative forced choice paradigm. Listeners had the greatest difficulty with the /ɪ-i/ and /ʌ-ɑ/ contrasts. Clear speech mode was not as effective for non-native speech as it has been shown for native speech. Implications are considered for social and clinical settings in which a mismatch in language backgrounds is present.

The findings support the use of clear speech for enhancing adult-to-child communication in AE in noisy environments.

Clear speech is an intelligibility-enhancing mode of speech that increases identification accuracy in various listening populations [e.g., Picheny et al. (1986)]. Children identify words more accurately in clear-speech sentences in noise than in conversational-speech sentences in noise [Bradlow et al. (2003)]. At the segmental level, adults identify clear-speech vowels in noise significantly more accurately than conversational vowels in noise, with some vowels benefiting more from clear speech than others [Ferguson and Kewley-Port (2002)]. However, little is known about the clear speech intelligibility benefit for vowels in noise as perceived by children. This study examined children’s identification of clear-speech vowels in noise. Four female adult speakers produced (/i-ε-æ-ʌ/) in carrier phrases in conversational and clear speech. Stimuli were then presented in speech-shaped noise to school-aged children at two signal-to-noise ratios. Children’s repetition of key words were recorded and coded by naive adult listeners. Results revealed children’s poorer vowel identification with decreased signal-to-noise ratio, and a greater clear-speech advantage in the poorer SNR, although listener-variability was evident. These data provide preliminary support for adults’ use of clear speech when communicating with children in adverse listening conditions.

This work has undergone a double-blind review by a minimum of two faculty members from institutions of higher learning from around the world. The faculty reviewers have expertise in disciplines closely related to those represented by this work. If possible, the work was also reviewed by undergraduates in collaboration with the faculty reviewers. AbstractSpeech-language pathologists may choose to evaluate children's language using standardized or naturalized assessments. This study investigated if the Clinical Evaluation of Language Fundamentals-Preschool 2 (CELF-P 2), a standardized assessment, and language sampling, a naturalized assessment, reveal the same information about children's linguistic competence and performance. Children ages 3.0-7.0 were assessed with specific focus on morphology and syntax. The participants completed four morphosyntactic-based subtests of the CELF-P 2. Additionally, play-based interactions, used to elicit natural language, were video-recorded. The CELF-P 2 was scored and language samples were transcribed and analyzed. Mean length of utterance (MLU) scores showed a slightly more variable trend around the mean than CELF-P 2 scores and there were no significant correlations between the two assessments. Furthermore, the two forms of assessment produced incongruous age equivalents for 66% of the participants (four out of six) and participants produced different morphosyntactic structures during each type of assessment. Thus, results indicated limitations and successes of the different assessment approaches. When used alone, either form of assessment did not provide a completely accurate representation of children's language acquisition. However, when used in conjunction, the two assessments may represent the linguistic competence and performance of children more accurately.