Effects of Environmental Noises on Fundamental Frequency Contours of Thai Expressive Speech

Problem statement: The expressive speech of Thai had been studied for a short period of time. An important feature of speech was fundamental frequency (F0) which defines the human speech prosody. It could be used to distinguish the difference between several types of expressive speech. The environmental noises affect the F0 contour for Thai dialects as concluded in the previous study. The study prosodic information of Thai speech with various speaking styles and several types of noises had not been conducted. Approach: Four different types of speaking styles were used; meanwhile four types of environmental noises were recorded with different levels of power. They were subsequently mixed together. The F0 contours from different types of speaking styles, different types of noises and different levels of noises were extracted. The Root Mean Square Error (RMSE) between the F0 contour of clean speech and the noise-corrupted speech was calculated. Results: In the experiments, four types of noises were included train, factory, car and air conditioner. Each type of speaking style included 10 samples of 10 utterances of male and female speech. Five levels of noises were varied from 0-20 dB compared with the clean speech. It could be notified that the effects of distinguishing types of noises were different. Four different types of speaking styles were also caused the differences in RMSEs. Conclusion: The recorded noises deteriorate the F0 contours for all types of speaking styles in Thai.