Acoustic and perceptual analyses of politeness in Japanese speech

In order to examine potential acoustic cues for politeness in Japanese speech, fO and temporal aspects of polite and casual utterances of two question sentences spoken by
six male native speakers were acoustically analysed. The analysis showed that fO movement of the final part of utterances and speech rate of utterance were consistently differently used in these different speaking styles (i.e., 'polite' and 'casual')across all the speakers. Perceptual experiments with listeners using a rating scale
method confirmed that these acoustic variables, which were manipulated using digital resynthesis, had an impact on politeness perception. It was showed that the duration
and fO direction of the final vowel of utterances were so influential that the overall impression of utterance politeness was changed. An experiment which used speech
rate variations of a polite utterance showed the important role of this variable in perceived politeness. Politeness ratings showed an inverted-U shape as a function of speech rate, but differed according to particular speakers. The speech rate of listeners was found to affect their utterance rate preference; listeners clearly preferred rates
close to their own, i.e., rates they perceived as 'natural' or comfortable. A final experiment, using speech rate variations of a polite utterance as stimuli and a two alternative forced-choice procedure, showed a very high correlation between perceived politenesss cores and naturalness scores. This suggests the importance of
listener characteristics in politeness research.