Soundproofing glossary definition of transmission loss

transmission loss :

Of a partition, for a specified frequency or frequency band, difference in decibels between the average sound pressure levels in the reverberant source and receiving rooms, plus ten times the logarithm of the ratio of the area of the common partition to the total Sabine absorption in the receiving room. Unit, decibel (dB); abbreviation, TL. The reduction in magnitude of sound between two locations.