Setting of the Values of the Parameters, H and M
   We have ever experimented to measure average cepstral distances (ACD) for different combinations of H (probability threshold) values and M (the number of mixture components in a segmental GMM) values. The measured values are listed in Table A. From Table A, it may be seen that the values of ACD under different combinations of H and M are very close, i.e. not sensitive to H and M. For example, the ACD ratio between (H=0.2, M=8) and (H=0.2, M=16) is 0.5220 / 0.5174 = 1.0089.


 Table A   ACD for combinations of H and M

H value

M (no. mix.)

0.1

0.2

0.3

0.4

0.5

8

0.5218

0.5220

0.5217

0.5216

0.5215

12

0.5196

0.5196

0.5194

0.5195

0.5195

16

0.5176

0.5174

0.5182

0.5182

0.5180

20

0.5203

0.5202

0.5200

0.5200

0.5196







Setting of the Values of the Parameters, K and α
   Since the values of ACD are not consistent with the signal quality of the converted voice, we originally tune the vales of K and α by listening to the converted voices. Now, we know that the measured values of variance ratio (VR) are almost consistent with the converted-voice quality. Therefore, we experiment to decide the values of K and α according to the measured VR values. The measured VR for different K values are listed in Table B whereas the measured VR for different α values are listed in Table C.

   From Table B, it is seen that the average VR is not sensitive to K (beam width for dynamic programming) value within the range, 16 to 32, but reach the maximum when K=24. Therefore, we decide to use K=24.

    From Table C, it is seen that the average VR is not sensitive to α (weighting factor) value within the range, 0.25 to 6. Thus, we cannot but to suspect whether VR cannot distinguish the converted-voice quality when VR values are close. Also, we cannot distinguish the converted-voice qualities when α is varied from 0.5 to 2 by perception. Therefore, we select to use α=1.5.

Table B  VR measured for different K values (under α=1.5)

K value

12

16

20

24

28

32

36

MA=>MB

0.6228

0.6239

0.6239

0.6248

0.6245

0.6239

0.6233

MA=>FA

0.5783

0.5798

0.5795

0.5793

0.5791

0.5795

0.5789

Average

0.6006

0.6019

0.6017

0.6021

0.6018

0.6017

0.6011



Table C  VR measured for different α values (under K=28)

α value

0.25

0.5

1.0

1.5

2.0

4.0

6.0

MA=>MB

0.6239

0.6241

0.6241

0.6245

0.6246

0.6247

0.6245

MA=>FA

0.5794

0.5796

0.5791

0.5792

0.5789

0.5788

0.5793

Average

0.6017

0.6019

0.6016

0.6019

0.6018

0.6018

0.6019