How do laboratory and field sound transmission loss test results vary?
For the laboratory testing, the products are tested in a closely controlled environment. The temperature and humidity conditions are controlled and very nearly the same on both sides on the test specimen. The test rooms are designed to provide a very uniform diffuse sound field on both sides on the sample. The rooms and filler walls are designed to minimize any exterior noises and to minimize any sound that might bypass (flank) the test specimen. The sound absorption of the receiving room is very low and it can be accurately determined. For testing in the field, however, most of these conditions can not be controlled. The temperature and humidity conditions are monitored, recorded and used in the calculations but they can not be closely controlled. Room sizes and absorption characteristics vary substantially from one project to the next and rarely do you find good diffuse sound field conditions. Exterior and interior noise sources can affect the test results if they are not eliminated
