Transmission loss

Transmission loss (TL) in general describes the accumulated decrease in intensity of a waveform energy as a wave propagates outwards from a source, or as it propagates through a certain area or through a certain type of structure.

It is a terminology frequently used in optics and acoustics. Measures of TL are very important in the industry of acoustic devices such as mufflers and sonars.

Definition[]

Measurement of transmission loss can be in terms of decibels.

Mathematically, transmission loss is measured in dB scale and in general it can be defined using the following formula:

TL = ${\displaystyle 10\log _{10}\left\vert {W_{i} \over W_{t}}\right\vert }$ dB

where:

• ${\displaystyle W_{i}}$ is the power of incident wave coming towards a defined area (or structure);
• ${\displaystyle W_{t}}$ is the power of transmitted wave going away from the defined area (or structure).

Applications[]

Transmission loss may refer to a more specific concept in one of the fields below:

• Transmission loss in electrical engineering describes the decrease of electrical power along an electrical cable. The term has its origins in telephony.
• Transmission loss in duct acoustics describes the acoustic performances of a muffler like system.
• Transmission loss in room acoustics describes the decrease of sound intensity that is reduced by a wall or other structure at a given frequency.
• Transmission loss in underwater acoustics describes the decrease of sound intensity that is reduced by a bubble curtain or other damping structure at a given frequency. The same term is sometimes used to mean propagation loss, which is a measure of the reduction in sound intensity between the sound source and a receiver, defined as the difference between the source level and the sound pressure level at the receiver.^[1]

References[]

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