A Diachronic Study(1965-2015) Of Prosody Change In American Broadcast News

This study explores prosodic evolution in the American TV news broadcast from the perspective of perception,by perceptual experiment based on acoustic analysis of audio archives.A corpus about 4 hours long covering five decades of broadcast news is retrieved half-automatically.Through statistical analysis,it is confirmed that the variance of pitch has a trend of constant increase throughout five decades,which means the rise and fall in speech intonation has become increasingly prominent and constant in the announcing style of major American television news broadcast.Before 1995,the increase is merely 6.46%,but after 2005 the pitch variance increased significantly by 17.40% compared to the 70 s and 80 s.And the divergence from the trend during the late 90 s and early 00 s can be explained in terms of historical and social factors.Based on what has been found in the corpus analysis,perceptual experiments were conducted to investigate whether or not the differences in intonation are perceived as correlate to time using synthesized material as stimuli in order to separate prosody features from voice quality effects and other irrelevant factors.The results indicate that the changes in the variance of pitch are perceived by listeners,especially that of the periods of pre-95 and 05~15.By manipulation the parameters of prosody transplantation,this study also finds that duration and intensity patterns do contribute to people's recognition of the time of the news broadcast;More specifically,duration and intensity patterns play a more important role than pitch in the recognition of the prosody of 95~99 news broadcast,while for 05~15 news broadcast,pitch patterns play a more important role than duration and intensity in the recognition of the prosody.This observation is compatible with the tenet of AM theory on the separation of intonation and stress.Furthermore,the accordance of the results of this diachronic research with the synchronic theoretical framework of AM verifies the principle of Blevins' s Evolutionary Phonology in that there are parallels between common types of sound change and common synchronic alternations.