{{Sound measurements}} '''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 radio communication, twisted pair systems (PTSN, Ethernet, etc.), optics and acoustics.<ref>{{Cite journal |last=Norton |first=Kenneth A. |date=January 1953 |title=Transmission Loss in Radio Propagation |journal=Proceedings of the IRE |volume=41 |issue=1 |pages=146–152 |doi=10.1109/JRPROC.1953.274172 |hdl=2027/mdp.39015077289554 |s2cid=51651739 |issn=2162-6634|hdl-access=free }}</ref><ref name=":0">{{Cite web |title=The FOA Reference For Fiber Optics - Measuring Power in dB and dBm |url=https://www.thefoa.org/tech/ref/testing/test/dB.html |access-date=2023-04-21 |website=www.thefoa.org}}</ref> 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 = <math> 10 \log_{10} \left\vert {W_i \over W_t}\right\vert</math> dB where: *<math>W_i</math> is the power of incident wave coming towards a defined area (or structure); *<math>W_t</math> 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.<ref>ISO 18405:2017 Underwater acoustics - Terminology (International Organization for Standardization, Geneva, 2017)</ref>
== Types ==
*Transmission loss types in fiber-optic communication include absorption loss, scattering loss, dispersion loss, radiation loss and coupling loss.<ref>{{Cite web |last=Sonali |date=2022-03-22 |title=What are the losses in Optical fiber? |url=https://www.goseeko.com/blog/what-are-the-losses-in-optical-fiber/ |access-date=2023-04-21 |website=Goseeko blog |language=en-US}}</ref><ref name=":0" /> *Transmission loss types in twisted pair transmission systems include conductor loss, dielectric loss as well as radiation loss.<ref>{{Cite web |title=Twisted pair |url=https://qucs.sourceforge.net/tech/node93.html |access-date=2023-04-21 |website=qucs.sourceforge.net}}</ref>
==References== {{reflist}}
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