Abstract
In this thesis, a prosody conversion system for Mandarin Chinese was developed in order to achieve (1) pitch conversion, (2) duration conversion, (3) energy conversion.UPDUDP (unbroken pitch determination using dynamic programming) is first applied to each utterance for pitch tracking which extracts an unbroken pitch contour from a given utterance based on time-domain acoustic feature of AMDF (average magnitude difference function) and DP (dynamic programming). Utterances are then segmented into phonemes using Viterbi forced alignment.The voiced parts of each utterance are then extracted to perform prosody conversion. Voice conversion is achieved by using PSOLA (pitch synchronous overlap and add) in time domain to adjust the fundamental frequency. WSOLA (waveform similarity overlap and add) is employed to adjust duration. Frame size is set to be the interval between one pitch mark and the next pitch mark of source wave and target wave. The volume for each frame is thus computed and linear mapping is performed. Energy conversion is then achieved by adjusting the source energy to the target energy.We have also made an attempt of using another approach of pitch tracking and speech synthesize called STRAIGHT (speech transformation and representation using adaptive interpolation of weighted spectrum) for voice conversion. The synthesized result of STRAIGHT is compared with that of PSOLA, and it is found that STRAIGHT can achieve better performance than PSOLA but requires more computation time.