Author: Nilsson A. C.
Publisher: S. Hirzel Verlag
ISSN: 1610-1928
Source: Acta Acustica united with Acustica, Vol.26, Iss.1, 1972-01, pp. : 1-18
Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.
Abstract
The sound transmission through a wall between two rooms depends on various boundary conditions.Cremer's fundamental theories for transmission losses for a panel were derived for an infinite wall and for a diffuse incident field. It is therefore of interest to find how a finite model modifies the results. Here it is assumed that two rooms are separated by a wall. All flanking walls are supposed to be acoustically hard and also the energy transmission between test panel and adjacent walls are neglected. In room 1 there is a sound source with a certain power output. The sound source will in turn excite the fields in room 1, in the panel and in room 2. The rooms and the wall constitute a coupled system. If the source is assumed to be known there are three unknown functions, namely for the sound fields in the rooms and for the panel displacement. By means of the three governing wave equations the three unknown fields can be solved as functions of the terms describing the source. These source terms depend not only on the power output but also on source position. Exact expressions – in the form of infinite series – can be derived for the various wavefields. When the velocity potentials are known then the space averages of the absolute values of the pressure squared follow directly. Also frequency averages can be derived.For two cases, a point source in a corner and for a completely diffuse primary field, it is particularly simple to derive explicit expressions describing the SPL difference between the rooms. Finally, the expressions for the point source can be generalized to apply to an ordinary loudspeaker. Thus, the final result is the difference between the levels in the rooms averaged over space and frequency.The boundary conditions for the wall determine the mode patterns for the flexural waves on the panel and also the wave field in room 2. It is found that the transmission loss is 3 dB higher for a simply supported panel than for a clamped panel when
Related content
Geometrical Acoustics for Rectangular Rooms
By Hirata Y.
Acta Acustica united with Acustica, Vol. 43, Iss. 4, 1979-11 ,pp. :