Abstract:

The behaviour of sound in rectangular enclosures in terms of modal approach and geometrical acoustics has been outlined. A program is provided to visualize the modes in a rectangular enclosure in terms of sound pressure, particle velocity and energy density. The requirements for reverberation chambers are discussed in terms of dimension ratios and the amount of absorption needed to ensure that all modes are excited uniformly. Especially at low frequencies the frequency spacing should be relatively small and without large fluctuations in value. A program is available to estimate the mode spacing parameters, based on the first 36 modes, of a reverberation chamber in terms of its dimension ratios. The 36 modes are listed in the program output in order of ascending frequency, and the type of mode is also given. Special consideration is given to reverberation chambers as facilities for the testing of space structures at high sound levels.