Statistical examination of invariance of relative F₀ change field for Chinese disyllabic words

Abstract

In automatic voice response systems where a large number of words are inserted into fixed sentences, such as in voice-guided car navigation systems, one of the most important problems is the adjustment of the fundamental frequency (F₀) contour of the inserted word to suit the F0 context of the fixed sentence. In Mandarin Chinese, it is required that the effects of tone and intonation on F₀ contours be represented separately. We proposed a scheme to solve the problem in terms of a word-level F₀ range (WF₀R) and a set of relative F₀ change fields. WF₀R in any position of a sentence is a tone-independent general F₀ range to represent the intonational effect; whereas F₀ change field (F₀CF) is an F₀ range that accounts for the result of both the tone combination of words and the intonation. Relative F₀CF is regulated in reference to WF₀R and represents tonal effect on F₀. In this paper, we statistically examine the invariance of the relative F₀CF with various speakers’ speech data. From an analysis of four native speakers’ utterances of 160 disyllabic words in the initial, middle and final parts of three carrier sentences, which were recorded on 2 or 3 days, it is found that: (1) Chinese speakers read words in the same sentence position with stable relative F₀CFs, even on different days; and (2) the relative F₀CFs in the middle position of a sentence are generally the same as those in the initial position but slightly different from those in the final position.