Quality assessment of synthetic speech using word intelligibility scores
Toshiro Watanabe · The Journal of the Acoustical Society of America · 1988
The quality of Japanese speech synthesized by rules cannot be sufficiently evaluated using only the 100-monosyllable list that has been used for speech articulation tests: Word intelligibility must also be assessed. Word intelligibility tests on both natural and synthetic speech were conducted to clarify the differences between synthetic and natural speech in learning effects, the effects of external noise, and word familiarity. Both trained and untrained listeners were used. Each word list of 155 words, selected by our previously developed method, reflected the most important word attributes of Japanese: word length, word familiarity, and initial phoneme occurrence. The experimental results show that the intelligibility scores for synthetic speech with untrained subjects were fairly low and independent of noise level. These were greatly improved by training, depending on the noise level. However, natural speech intelligibility depends little on training. The results also show that the familiarity of the test words and the first phoneme in the word are important factors in recognizing Japanese words in both synthetic and natural speech.