Régime sonore d'une salle après l'extinction de la source

When a source of sound, acting in a room, is suddenly stopped, a free regimen sets up, the extinction of which the elementary theory predicts, following an exponential law with an attenuation which depends only upon the volume of the room and the total absorption of its lining. A theoretical study, followed by experimental verification done in the reverberation room at the Centre de Recherches Scientifiques, Industrielles et Maritimes de Marseille, has shown that in a parallelopiped-shaped room with located absorption, the reverberation time changes with the position of the absorbent. The theory of Sabine is insufficient for measurement in the laboratory of coefficients of absorption. However, it gives the only usable approximation for high-pitched sounds. For low enough frequencies the author develops a more precise theory, making it possible to predict the variations of the reverberation-time.