Sound propagation from the inside to the outside of a room through an aperture

Abstract

A calculation method for the sound field propagated through an aperture of a room is presented in this paper. In a very large room as compared to the wavelength concerned, the sound can be assumed to be diffused. In such a case it is more practical to calculate the sound field radiated from an aperture by Kirchhoff's diffraction formula than by an integral equation method. This formula requires both the velocity potential and its normal derivative on the aperture which are not known exactly. These unknowns can be estimated approximately by geometrical acoustics. Calculated examples based on this method and the corresponding measurements are presented. For low frequencies the above method can not be applied. In the last section such a special case is discussed, namely a room shaped like a rigid and thin pipe which stands on rigid ground. A point source is located at the centre of the floor in the ‘room’ and the sound is radiated from the open top. The sound field is calculated by means of an integral equation method. Numerical examples are presented with the measurements.