Sound Transmission Loss or Transmission Loss (TL)

A measure of the reduction in magnitude of sound intensity in a transmission system.

The loss due to geometric spreading (see sound propagation) is called divergence loss. By implication, transmission loss is also a measure of sound insulation in a structure. It is calculated from the equation:

TL = 10 log₁₀ (1/s) (dB)

where s is the Sound Transmission Coefficient.

See: Sound Transmission Class. Compare: Absorption Coefficient, Noise Reduction Coefficient, Reflection Coefficient.