Disfluencies in change detection in natural, vocoded and synthetic speech

In this paper, we investigate the effect of filled pauses, a discourse marker and silent pauses in a change detection experiment in natural, vocoded and synthetic speech. In natural speech change detection has been found to increase in the presence of filled pauses, we extend this work by replicating earlier findings and explore the effect of a discourse marker, like, and silent pauses. Furthermore we report how the use of "unnatural" speech, namely synthetic and vocoded, affects change detection rates. It was found that the filled pauses, the discourse marker and silent pauses all increase change detection rates in natural speech, however in neither synthetic nor vocoded speech did this effect appear. Rather, change detection rates decreased in both types of "unnatural" speech compared to natural speech. The natural results suggests that while each type of pause increase detection rates, the type of pause may have a further effect. The "unnatural" results suggest that it is not the full pipeline of synthetic speech that causes the degradation, but rather that something in the pre-processing, i.e. vocoding, of the speech database limits the resulting synthesis.