Effects of Noises on the Analysis of Fundamental Frequency Contours for Thai Speech

Problem statement: In speech communication, noises from surrounding environments affect the communication quality with various aspects. The received speech quality should be analyzed to see how the important noises reduce the speech quality so that we can eliminate them in an appropriate way. Approach: This study presents a study on the analysis of the noise effects on Thai speech. Four kinds of noises; air conditioner, car, factory and train, are chosen to be simulated in the study. The various levels of signal-to-noise ratios are conducted. The root mean square error between the fundamental frequency contours of the corrupted speech and the clean speech is calculated. Finally, the analysis of the root mean square error in terms of comparisons among genders, the four kinds of noises and various levels of signal-to-noise ratios is performed. Results: In the experiments, 400 speech utterances of male and female are used as speech materials. The average values of root mean square error are calculated. The results show that the fundamental frequency contour of female speech is affected more than that of male speech. Comparing among four kinds of noises, the car noise has the highest influence, while the factory noise has the lowest influence. Moreover, the root mean square error is inversely proportional to the level of signal-to-noise ratio. Conclusion: From the finding, the noises from surrounding environments have affected the speech quality of fundamental frequency contour. This study is the preliminary knowledge to enhance the speech quality for further works such as speech synthesis systems or other speech processing technologies.