Natural vs. Synthesized Speech in Spoken Dialog Systems Research ?? Comparing the Performance of Recognition Results

In this paper, we test the effect of using speech synthesis when interacting with a spoken dialog system (SDS). We use a user simulation to connect our speech synthesis to a real, state-of-the-art automatic speech recognition (ASR) component deployed in a working commercial SDS via a standard telephone line. In a series of experiments, we compare human-machine dialogs and their recognition scores with simulated dialogs using synthesis. Our results show that a good text-to-speech synthesis configuration rivals human speech both in recognition scores as well as variability. This makes the speech interface in user simulation quite attractive.