Effect of Splayed Walls of a Room on the Steady-State Sound Transmission Characteristics

Abstract

The steady-state sound transmission characteristics of a fan-shaped room, taken as an example of a splayed room, were analyzed mathematically. The wave-type factors “en,” developed by Morse and others, and the distribution of the normal modes of such a room were compared with those of a rectangular room. The fan-shaped room with ρ0≃1.2∼1.4 has good characteristics in the low-frequency region, where ρ0 is the ratio of the outer and inner radius of the room. And such a fan-shaped room corresponds to a splayed room with l/a≃0.09∼0.17 where a is the mean length of the parallel walls and 2l is the difference between them. The transmission characteristics in model rooms of various shapes were measured. The shape of the model was varied from the rectangle to trapezoid and to quadrangle with nonparallel walls, while keeping the interior volume of the room constant. The experimental results, obtained on the decrease of the frequency irregularity in the transmission characteristics of a trapezoid room, showed a good agreement with the theoretical results and our experiences.