Perception of Speech Rate and Naturalness in Synthetic Slow Speech

This paper details two perception experiments based on synthetic British English obtained with CART models predicting phone durations in slow speech from normal speed speech. Speech rate and naturalness were assessed by 6 English natives. Synthetic slow speech was rated as both slower and less natural than natural slow speech; however, the insertion of the pauses produced in natural slow speech into the synthetic recordings suggests a better approximation of natural speech in terms of both naturalness and perceived speech rate.