Nguyễn Tiến Thành - Vietnamese speech synthesis for assistant services on mobile devices Page ii

Nguyễn Tiến Thành - Vietnamese speech synthesis for assistant services on mobile devices Page iii

COMMITMENT

I commit myself to be the person who was responsible for conducting this

study. All reference figures were extracted with clear derivation. The presented

results are truthful and have not published in any other person‟s work.

Nguyễn Tiến Thành

Nguyễn Tiến Thành - Vietnamese speech synthesis for assistant services on mobile devices Page iv

Special thanks to my supervisor Dr. Mạc Đăng Khoa and colleagues of Speech

Communication Department, MICA Institute for their advice and encouragement

they gave to me, especially Assoc. Prof. Trần Đỗ Đạt for their thorough review and

invaluable suggestions

I would like to thank to Mr. Nguyễn Mạnh Hà and Ms. Nguyễn Hằng Phương

for their guide in recording the corpus. I would also like to thank to a lot of MICA

members, who spent much of time for testing for my research.

I am grateful to Prof. Eric Castelli, Dr. Nguyễn Việt Sơn and MICA‟s

directorate for supporting me the best working conditions in MICA International

Research Institute.

Nguyễn Tiến Thành - Vietnamese speech synthesis for assistant services on mobile devices Page v

et al. 2001) ................................................................................................................... 6

Figure 1-3 Glottal airflow and the resulting sound pressure at the mouth (Rabiner

and Juang 1993) .......................................................................................................... 7

Figure 1-4 Waveform plot of the beginning of the utterance “It‟s time”(Huang et al.

2001)............................................................................................................................ 8

Figure 1-5 Signal of sound “my speech” and its spectrogram .................................... 9

Figure 1-6 Speech recognition and speech synthesis (Chandra and Akila 2012) ..... 10

Figure 1-7 Schematic of text-to-speech synthesis ..................................................... 11

Figure 1-8 A schematic of the construction of an articulatory speech synthesizer and

how a such a synthesizer may be considered to contain a model of information

Figure 1-11 General HMM-based synthesis scheme (Zen et al. 2009) .................... 19

Figure 1-12 A diagram of the Hunt and Black algorithm, showing one particular

sequence of units and how the target cost measures a distance between a unit and

the specification, and how the join cost measures a distance between the two

adjacent units (Taylor 2009) ..................................................................................... 25

Figure 2-1 Schematic diagram of Hanoi Vietnamese tones (Michaud 2004) ........... 35

Figure 2-2 Base system of Vu Hui Quan consists of 2 parts: training part and

synthesis part.(Quan and Nam 2009) ........................................................................ 36

Figure 2-3 Vietnamese speech recognition system (Vu et al. 2006) ........................ 37

Figure 2-4 Non-uniform unit selection model (Van Do et al. 2011) ........................ 38

Nguyễn Tiến Thành - Vietnamese speech synthesis for assistant services on mobile devices Page vi

Figure 3-6 Sub-cost based on the difference in position of phrase ........................... 49

Figure 3-7 Sub-cost based on the difference in context of preceding syllable and

following syllable ...................................................................................................... 50

Figure 3-8 Syllable “Quanh” is composed of four phonemes .................................. 51

Figure 3-9 Sub-cost based on the difference in context of preceding phoneme and

following phoneme .................................................................................................... 51

Figure 3-10 Acoustic units network .......................................................................... 56

Figure 3-11 The algorithm of separating sentence into as long as possible phrases 57

Figure 3-12 Finding the longest phrase in database .................................................. 58

Figure 3-13 Search space before applying acoustic units network ........................... 59

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Table 2-3 Advantages and disadvantages between two synthesis systems of Quan

and Thao .................................................................................................................... 40

Table 3-1 Position difference and cost value (min is better). Target unit is begin or

end of sentence .......................................................................................................... 48

Table 3-2 Position difference and cost value (min is better). Target unit is both

begin and end or is middle of sentence. .................................................................... 48

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from the lung to the trachea (or windpipe), the tensed vocal cords within the larynx

are caused to vibrate (in the mode of relaxation oscillator) by the air flow. The air

flow is chopped in to quasi-periodic pulses which are the modulated in frequency in

passing through the pharynx (the throat cavity), the mouth cavity, and possibly the

nasal cavity. Depend on the positions of the various articulators (i.e. jaw, tongue,

velum, lips, mouth) different sounds are produced.

The glottal air flow (volume velocity wave form) and the resulting sound

pressure at the mouth for a typical vowel sound is shown in Figure 1-3. The glottal

waveform shows a gradual build-up to a quasi-periodic pulse train of air, taking

about 15 ms to reach steady state. This build-up is also reflected in the acoustic