The aim of the present empirical study is two-fold. The first aim is to investigate why Thai university students perceive a certain tone better than others or why a certain tone is more difficult to perceive than others. The second aim is to examine to what extent Thai university students can perceive four Chinese Mandarin tones. 14 volunteer university students (2 males; 12 females) participated in the study. Research tools were structured interview and the perception test. The findings from the interview reveal that 9 out of 14 (64%) students claimed that tone 4 was the easiest tone either to perceive or produce. In contrast, 10 out of 14 (71%) stated that tone 3 was the most difficult one to perceive. The qualitative data findings from the interview were greatly consistent with the quantitative data ones from the perception test. That is, Thai speakers performed well in tone 4 (mean scores 24.92 or 99.68%) and tone 1 (24.35 or 97.40%). On the other end of the scale, they had some difficulty identifying tone 2 (21.42 or 85.68%) and tone 3 (19.50 or 78%). It can be concluded that firstly, the hierarchy of tone accessibility from the least difficult to the most difficult one was tone 4 > tone 1 > tone 2 > tone 3. Secondly, students' native language (Thai) or L1 plays a crucial role to their tonal acquisition when Thai speakers deal with foreign lexical tones. For one important reason, tones 1 and 4 in Chinese are very similar to the mid tone and the falling tone in Thai, respectively.

The pronunciation of regular past tense verbs seems to be difficult for most L2 learners, especially in L2 learners whose first language phonological system is different from the English one. It is predicted that Thai EFL students could encounter difficulties perceiving English coda clusters like the '-ed' ending sounds. For this reason, this research investigates the extent to which the first-year and the third-year English major undergraduate students in a public university perceive the English regular past tense verbs. To be precise, this study compares the ability to perceive the regular past tense of the first-year and third-year students. In addition, the strategies they use to perceive the '-ed' ending verbs among the three different allomorphs ([t], [d] and [ɪd]) are investigated. The data collection was derived from the perception tests of 30 first-year and 30 third-year students and a Pronunciation Learning Strategy (PLS) questionnaire. The perception tests were divided into two subtests: perception test and perception syllable identification test. The PLS questionnaire was employed to find out the strategies they used in English pronunciation learning. The overall results show that the third-year students demonstrated a better performance than the first-year students in both tests (t=-2.778; p<.01 in the perception test; t=-1.466; p>.05 in the syllable identification test). However, the syllable identification test's results do not show consistency with Solt et al.'s (2004) model, while the perception test's do. Moreover, the findings from the questionnaire reveal no statistically significant difference between the first and the third-year students in terms of pronunciation learning strategies (p>.05).

Attempts to account for consonant cluster acquisition are always made into two aspects. One is transfer of the first language (L1), and another is markedness effects on the developmental processes in second language acquisition. This study has continued these attempts by finding out how well Thai university students were able to perceive English onset and coda clusters when they were second year and fourth year students. This paper also aims to investigate Thai speakers' opinions about their listening and speaking skills, and whether their course subjects enhanced their performance. To fulfil the first objective, a pretest and posttest were launched to measure how the 34 Thai participants were able to identify 40 onset and 120 coda clusters at different periods of time. The statistical findings show that even though their overall scores in the fourth year were higher than those in the second year, there was no statistically significant difference in both major types of clusters [t = -1.29; p value >0.05 in onsets; t = -0.28; p value >0.05 in codas]. The Thai participants performed slightly better in onset (84% / 86%) than in coda (70% / 71%). To complete the second objective of the study, a 24-item questionnaire was distributed to the participants. The responses indicated positive opinions about their listening and speaking skills and the English courses they took in a four-year study. However, they still had difficulty identifying some English consonant clusters even though those were widely used or found. Finally, most participants claimed that English Phonetics and Phonology Course was one of the significant course subjects instrumental in establishing their fundamental knowledge of how to pronounce English words and develop their listening skill as well.

Cochlear implant (CI) listeners encounter difficulties in communicating with other persons in noisy listening environments. However, most CI research has been carried out using the English language. In this study, single-channel speech enhancement (SE) strategies as a pre-processing approach for the CI system were investigated in terms of Thai speech intelligibility improvement. Two SE algorithms, namely multi-band spectral subtraction (MBSS) and Weiner filter (WF) algorithms, were evaluated. Speech signals consisting of monosyllabic and bisyllabic Thai words were degraded by speech-shaped noise and babble noise at SNR levels of 0, 5, and 10 dB. Then the noisy words were enhanced using SE algorithms. The enhanced words were fed into the CI system to synthesize vocoded speech. The vocoded speech was presented to twenty normal-hearing listeners. The results indicated that speech intelligibility was marginally improved by the MBSS algorithm and significantly improved by the WF algorithm in some conditions. The enhanced bisyllabic words showed a noticeably higher intelligibility improvement than the enhanced monosyllabic words in all conditions, particularly in speech-shaped noise. Such outcomes may be beneficial to Thai-speaking CI listeners.

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