Problem statement: Tone of a tonal language is an important feature of a prosodic syllable to identify the meanings of that syllable or that part of word. Ii is very crucial to model the feature related to tone of speech to achieve the most naturalness in speech communication. Approach: The study presents an approach to analyze the model parameters of Thai tones for two genders. The successive modeling of fundamental frequency, Fujisaki’s model is selected. We derive seven parameters; baseline frequency, the numbers of phrase commands and tone commands, phrase command and tone command durations, amplitudes of phrase command and tone command. Results: In the experimental results, there are 20 syllables and each syllable includes 50 samples of a tone with male and female speech. Five tones are recorded in the same environment. Thereafter, there are ten thousands samples in the speech corpus. It can be obviously seen that Thai tones are determined by the derived parameters. Conclusion: All in all, Thai tones are able to be discriminated by the derived parameter of Fujisaki’s model.

Problem statement:The bitrate scalability is an important functionality that is defined in the Moving Picture Expert Group (MPEG-4) requirements. Since the traffic in a communication network varies with time, the capability of varying the bitrate of a speech coder is needed. Approach: This study proposes an approach to vary the bitrate by using a bitrate scalable tool which is attached with the core section of Multi-Pulse based Code Excited Linear Predictive (MP-CELP) coder. The bitrates scalable tool employs multi-stage excitation coding based on an embeddedcoding approach. The multi-pulse excitation codebook at each stage is adaptively produced depending on the selected excitation signal at the previous stage. Results: The experimental results show that the speech quality of the proposed coder with the bitrate scalable tools is improved above the speech quality of the conventional coder. Conclusion: From the study, the proposed approach gives a tool to improve the speech compression and can also support a variety of coder bitrates.