Acoustic Variability in the Speech of Children with Cerebral Palsy

Acoustic variability in the speech of children with cerebral palsy Li-mei Chen+ Han-chih Ni* Tzu-Wen Kuo* Kuei-Ling Hsu* Department of Foreign Languages and Literature National Cheng Kung University + Associate Professor, leemay@mail.ncku.edu.tw *Undergraduate students, mspasaya@gmail.com, sls15239@hotmail.com, ling1991411@hotmail.com ��� ������������������������������������ �������������������������������������� ������������������ ��������������������� ����������������������� ����������������� ����������������������� ���������������� �������������������������������������� ����������������� ������������������������� Abstract This study examines the acoustic variability in four 4-year-old children: two with cerebral palsy (CP) and two typically developing (TD). One recording from each child, collected from the picture-naming task and spontaneous interaction with adults was analyzed. Acoustic vowel space, pitch and speech rate in their production were investigated. Study findings indicated the following: 1) children with CP have a smaller vowel space than TD children, and there was a scattered distribution of the formant frequencies in CP; 2) children with CP tend to spend more time producing the utterances and their production of tones was unstable; and 3) both the speech rate and speech intelligibility in CP were lower. Future studies are needed to verify these preliminary findings. The variability features in the production of children with CP provide important references in speech therapy. Keywords: Mandarin-speaking children, cerebral palsy, vowel space, fundamental frequency, speech rate 1. Introduction Cerebral palsy is a common speech motor disability in children, and an umbrella term to indicate a neurologic developmental condition that affects individuals from early childhood throughout their lifespan [1]. Due to the neurologic factors, children with cerebral palsy tend to have several types of speech deficits. According to a previous study [2], 60% of children with CP have some type of speech deficits, among which dysarthria, the most common Proceedings of the Twenty-Fourth Conference on Computational Linguistics and Speech Processing (ROCLING 2012) 15 speech disorder found in individuals with CP, has received more attention. This study focuses on the acoustic aspects of dysarthria: vowel space, pitch, and speech rate. Vowel space is an acoustic measure that indicates the jaw’s coordination and the tongue’s controlling ability [3]. Because of poor muscle coordination, individuals with dysarthria tend to have a smaller vowel space, which influences the accuracy of articulation and reduces the intelligibility of their speech. Moreover, because dysarthric speakers have a hard time controlling their respiratory and the laryngeal mechanisms, it is difficult for them to produce correct tones, which plays an important role in the intelligibility of tonal languages ([2], [4], [5]). Furthermore, the stability of the speech rate affects listeners’ intelligibility, but dysarthric speakers usually present a rate disturbance [6]. Therefore, these three acoustic measures are vital to the speech of the individual with dysarthria. By analyzing these three measures, this study provides a preliminary index of cerebral palsied speech and a direction for speech-language intervention. 2. Literature review 2.1 Acoustic vowel space Many researchers have used vowel space as an index for the size of the vowel articulatory working space, the accuracy of vowel articulation, and the tongue’s controlling ability ([3], [7]). Moreover, the influences of dysarthria and unclear speech on the sizes of vowel areas and the relationship …

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