Effects of Environmental Noises on Fundamental Frequency Contours of Thai Dialects

Problem statement: Fundamental Frequency (F0) is an important speech feature defining the human speech prosody. It is the resultant of the vibration of human’s vocal chords in speech production. In Thai, there are four main dialects spoken by Thai people residing in four core region including central, north, northeast and south regions. Environmental noises are also playing an important role in corrupting the speech quality. The study of effects of noises the F0 contour for Thai dialects reveals the important of noise reduction issue. Approach: Four types of environmental noises were recorded with different levels of power. It was subsequently mixed with clean speech. The F0 contours from different dialects, different types of noises and different levels of noises was extracted. The difference in term of Root Mean Square Error (RMSE) between the F0 contour of clean speech and the noise-corrupted speech was calculated. Results: In the experiments, each regional dialect includes 10 samples of 10 utterances with male and female speech. Four types of noises include train, factory, car and air conditioner. Moreover, five levels of each type of noise are varied from 0-20 dB. The results show that effects of distinguish types of noises are different. Four kinds of regional dialects also cause the differences in RMSEs. Conclusion: The recorded noises deteriorate the F0 contours for all Thai dialects.