What is speech intelligibility?

Abstract

Speech intelligibility is an important factor but is partly considered for each purpose. The intelligibility of clean speech is difficult to be quantified, although the speech intelligibility indexes in noisy and reverberant environments are widely standardized. In this study, the relationship between the vowel space and subjective impressions is investigated for Japanese five vowels. The vowel space, that is the pentagon defined by the first and second formant frequencies, is considered in the Equivalent Rectangular Bandwidth scale, which is an auditory-oriented, non-linear frequency scale. Concerning the subjective evaluation, a listening test is carried out with five grade scale on subjective fluency and so on. It is found that the skewness of the vowel space is highly correlated with the subjective fluency of vowels.