New Developments in Speech Recognition for Car Navigation System

1. Introduction Mitsubishi Electric is striving to improve speech recognition capabilities for the car navigation system. One of the key problems encountered is when the user speaks out-of-vocabulary words which cannot be recognized. To solve this problem, the speech recognition system was equipped with a smart POI (point of interest) search function (1) , which automatically generates variations of each POI name in the recognizable vocabulary. However, along with the expanded vocabulary, both the cost of updating the word variation list and the amount of computation increased. In addition, the same problem has also occurred regarding command and control by voice. Acceptable expressions are limited to those listed in the manual, thus no variations are recognized. Consequently, we divided the system into two parts: the speech recognition part that converts the input speech into a character string and the post-processing part that performs the text match processing, and we developed a new speech recognition system that avoids an increase in computation when the number of words increases. This paper describes the newly developed speech recognition and post-processing technologies, as well as the voice interface installed in commercial products.