How does the field sound transmission class relate to the value measured in the laboratory?
There is some controversy over this issue. If there is significant flanking transmission in a building, the apparent sound transmission class will be lowered. One can expect to get ratings as much as 5 dB lower in the field than those obtained in the laboratory, but with good construction practice, values almost as high as those in the laboratory can be achieved. • If the sound insulation were measured for a large number of party walls in an apartment, would the FSTC ratings vary significantly? This is an area where not enough is known. A certain amount of variation is associated with the test procedure itself, but this is small relative to the amount of variation associated with the building. This will be determined by the degree of care used to make sure that partitions and floors are identical, and constructed properly and that there is no flanking transmission. However, if a field test is performed and the field sound transmission class is found to be 5 dB lower than the expected v
