R. E. Halliwell
J. D. Quirt
A. C. C. Warnock
IRC, Natl. Res. Council, M27 Montreal Rd., Ottawa, ON K1A 0R6, Canada
The pair of reverberation room that have been used at National Research Council Canada for about 30 years, are deemed too small by current ASTM standards. A new pair of rooms that incorporate some interesting ideas to satisfy the requirements and recommendations in both ISO and ASTM standards has just been constructed. One vertical cross section through each room is a five-sided polyhedron. The test specimen is at one of the sides. This design allows the room volumes to be large (about 175 cm[sup 3] each), the specimen to be a normal size, and yet to be one complete surface of the room. The niche between the two room is minimal. Both rooms are resiliently supported as is the floor support. The upper room is of a lightweight construction and the lower is of poured concrete. Floors are constructed on wheeled, heavy concrete frames that can be moved in or out of the slot between the rooms. A crane outside the room allows other test frames with floors already constructed to be inserted into the specimen opening. Some details of the design will be presented as well as sound transmission results from reference specimens from all three pairs of rooms at NRC. These differ quite markedly in size and results for receiving rooms ranging from 65--250 cm[sup 3] can be compared. A small amount of a detailed examination of the sound fields in the rooms based on measured and calculated data will be presented.