TM 5-805-4/AFJMAN 32-1090
the square of a reference pressure. Therefore, the
Transmission Loss of Building Partitions". It is
sound pressure level is equal to 20 times the
designed to give an estimate of the sound insula-
common logarithm of the ratio of the sound pres-
tion properties of a partition or a rank ordering of
sure to a reference pressure (20 micropascals or
a series of partitions.
0.0002 microbar).
Sound Transmission Loss (TL)
Sound Transmission Class (STC)
A measure of sound insulation provided by a
A single-number rating derived from measured
structural configuration. Expressed in decibels,
values of transmission loss in accordance with
it is ten times the common logarithm of the
ASTM E-413, "Classification for Rating Sound
sound energy transmitted through a partition, to
Insulation" and ASTM E-90, "Test Method for
the total energy incident upon the opposite
Laboratory Measurement of Airborne Sound
surface.
Glossary-2
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