attenuation

at·ten·u·ate   (ə-těn'yōō-āt')    v.   at·ten·u·at·ed, at·ten·u·at·ing, at·ten·u·ates v.   tr. To make slender, fine, or small: The drought attenuated the river to a narrow channel. To reduce in force, value, amount, or degree; weaken: Medicine attenuated the fever's effect. To lessen the density of; rarefy. Biology To make (bacteria or viruses) less virulent. Electronics To reduce (the amplitude of an electrical signal) with little or no distortion. v.   intr. To become thin, weak, or fine. adj.   (-yōō-ĭt) Reduced or weakened, as in strength, value, or virulence. Botany Gradually tapering to a slender point. [Latin attenuāre, attenuāt- : ad-, ad- + tenuāre, to make thin (from tenuis, thin; see ten- in Indo-European roots).] at·ten'u·a'tion n.

Main Entry: at·ten·u·a·tion
Pronunciation: &-"ten-yu-'wA-sh&n
Function: noun
: a lessening of the amount, force, or magnitude of something; specifically : a weakening of the connection between an illegal police procedure and the evidence obtained by it such that the evidence is admissible at trial as an exception to the exclusionary rule

Main Entry: at·ten·u·a·tion
Pronunciation: &-"ten-y&-'wA-sh&n
Function: noun
: a decrease in the pathogenicity orvitality of a microorganism or in the severity of a disease

attenuation at·ten·u·a·tion (ə-těn'y&oomacr;-ā'shən)
n.

1. A dilution, thinning, or weakening of a substance, especially a reduction in the virulence of a pathogen through repeated inoculation, growth in a different culture medium, or exposure to heat, light, air or other weakening agents.

2. The energy loss of an ultrasonic beam as it passes through a material.

attenuation 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].
(2003-07-29)