Abstract:
This acoustic study focuses on the phonetic phenomenon in English called the voicing effect in which vowel duration followed by voiced consonants is longer than those followed by voiceless consonant counterparts. This study aims to 1) study the duration of English vowels preceding voiced consonants longer than vowels preceding voiceless consonants, which are produced by L1 Thai speakers. 2) investigate the influence of English tense and lax vowels on the vowel duration ratio regarding voiced and voiceless final consonants, which are produced by L1 Thai speakers. Participants include 10 students studying at Chulalongkorn University from various faculties. The research instruments consisted of a pronunciation task. The vowel duration values were measured by Praat and analyzed by descriptive statistics. The results showed that Thai speakers inconsistently used voicing effect. They also exhibited the unexpected results called countervoicing effect which is when the vowel duration preceding voiceless consonants tends to be longer than the vowel duration preceding voiced consonants. It was found that most of the vowels which yield countervoicing effect were lax vowels. Thai speakers must be explicitly instructed in order to acquire the use of voicing effect.
