Attenuation

1. In biology, attenuation is a mechanism in the regulation of gene expression

2. In ecology and geochemistry, attenuation is the ability to withhold contaminants in soils and groundwaters by various mechanisms like adsorption, dilution[?], dispersion or biological degradation, causing a lower toxicity compared to the total amount of the contaminant.

3. In telecommunication, attenuation is the decrease in intensity of a signal, beam, or wave as a result of absorption of energy and of scattering out of the path to the detector, but not including the reduction due to geometric spreading.

Note 1: Attenuation is usually expressed in dB.

Note 2: "Attenuation" is often used as a misnomer for "attenuation coefficient[?], " which is expressed in dB per kilometer.

Note 3: A distinction must be made as to whether the attenuation is that of signal power or signal electric field strength.

Source: from Federal Standard 1037C and adapted from the Department of Defense Dictionary of Military and Associated Terms