Comparative study of speech intelligibility inside cars

The paper describes the results of comparative study of speech intelligibility inside some cars for assessing the direct speech communications between the passengers and the performance of hands-free communication devices. Especially the same car has been studied changing configuration of sound insulation, sound absorption and electronic sound reproduction systems to find new principles for optimizing speech intelligibility. The measurement system is based on the use of two head and torso simulators, one equipped with an artificial mouth, the second equipped with binaural microphones. The results show how an excessive use of sound absorbing material lowers the background noise, but does not improve the speech intelligibility, because it damps too much the sound reflected by the internal surfaces.