How is sound insulation measured ?

The measurement method depends on the particular situation. There are
standards for the measurement of the insulation of materials in the
laboratory, and for a number of different field circumstances. Usually
the procedures involve generating a loud sound of a specified type and
monitoring the transmitted noise.

It is very useful to have a single number to characterize the
insulation of a partition. Measurements are often conducted in third-
octaves, and the reduction plotted on a graph. A reference curve is
then fitted to the measurements using a specified procedure, and the
value of this curve at 500 Hz is taken as the figure. There is a slight
difference in procedure between the U.S. and ISO standards, but the
methods are basically similar. The same is also true for impact noise
transmission assessment, where a standard tapping machine is in use to
hammer floors. Sound pressure levels in the room below are monitored.