Evolution spatiale de l'intelligibilité de la parole dans un habitacle automobile

Abstract
In a car, speech intelligibility primarily depends on the ratio between speech and noise levels. The speech level, as perceived by the listener, is influenced by the compared positions of the speaker and the listener and the characteristics of the car cabin (its geometry and materials). In this study, the Articulation Index was used to evaluate speech intelligibility in different positions in the compartment of a luxury sedan car, for two sound sources : an omnidirectionnal one and a loudspeaker whose directivity is the same as a human speaker's. The effect of human's directivity is to decrease speech intelligibility, especially in cases where the communication is difficult (from the front seats to the rear ones). These measurements were also compared with simple models of sound field in the car (free field and diffuse field). For an omnidirectional source, the field is nearly a free one ; for a directional one, the surfaces of the cabin can reflect sounds to increase the level, but this increase is not equivalent to what can be seen in a diffuse field. Therefore, the geometry and absorption characteristics in a car compartment could be modified in order to improve communication between passengers.