Implementation of a New Metric for Assessing and Optimizing the Speech Intelligibility Inside Cars

The speech transmission index (STI), which was first developed for room acoustics and telecommunication systems purposes, aims at assessing the quality of the transmission of speech within a given acoustic channel. Rieter Automotive AG is currently implementing and evaluating this metric for the automotive field. The major difference between the STI and the widely used Articulation Index (AI) is that the calculation of STI takes into account both, the background noise at the talker's position and the alteration of the of the speech signal due to its transmission between the talker and the listener.

In this paper, the different stages for the implementation of this metric in the automotive industrial context are highlighted. Especially, the designing of specific equipment for running a reliable measurement is tackled, and an example of the utilization of this metric is given.