Frequency Modulation Technique for Prosodic Modification

Modulation of speaking tone in frequency can make speech interesting and convey subtle meaning in communication. We present a frequency modulation (FM) technique for prosodic modification to consider communicative speech synthesis. This technique provides a mathematical formulation for representing speaking tone and manipulating FM in a unified framework. Two experiments are conducted with a text-to-speech system to which a module of FM-based prosodic modification is added. One is to enhance emphasis in words when synthesizing Chinese conversational speech. The other is to modify reading- style prosody while conveying good and bad news in Japanese; this is done by using the FM technique to shift the frequency ranges and rescale the fundamental frequency contours jointly. The experimental results indicated that the native speakers identified 90% of samples with emphases and 78% of "good news" as well as 94% of "bad news" samples. The FM technique is vital for making synthetic speech communicative.