Purpose: To assess the effects of speech therapy on the acoustic characteristics of speech in a group of cleft lip and palate patients. Materials and methods: In this experimental pilot study, eight patients with unilateral cleft lip and palate participated in the 13-month period of speech therapy. They had some exercises in the class and at home to reduce the hypernasality of speech. Using an acoustic software named Praat, three formants (F1, F2, F3) of speech sounds /b/, /p/, /f/, /v/, /k/, and /g/ were obtained pre and post speech therapy. We used paired samples t-test to compare the acoustic variables of each consonant before and after the therapy. Results: No significant differences were found between the pre- and posttherapy acoustic measures for fricative consonants /f/, /v/ and stop consonants /k/ and /g/. However, a statistically significant improvement in hypernasality of labial consonants /b/ and /p/ was observed after the speech therapy. Conclusions: The present study underlines the role of a speech therapist in a complete cleft care team, in order to take care of the speech improvement of the patient and to motivate the parents to help the speech development of their child.

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