<communications> The progressive reduction in amplitude of a signal as it travels farther from the point of origin.

For example, an electric signal's amplitude reduces with distance due to electrical impedance. Attenuation is usually measured in decibels [per metre?].

Attenuation does not imply appreciable modification of the shape of the waveform (distortion), though as the signal amplitude falls the signal-to-noise ratio will also fall unless the channel itself is noise free or the signal is amplified at some intermediate point(s) along the channel.

["Networking Essentials, second edition", Microsoft Corporation, pub. Microsoft Press 1997].

(01 Aug 2003)

<radiobiology> Process by which a beam of radiation is reduced in intensity when passing through material - combination of absorption and scattering processes, leading to a decrease in flux density of beam when projected through matter.

(16 Dec 1997)