attenuation


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Attenuation

The reduction in level of a transmitted quantity as a function of a parameter, usually distance. It is applied mainly to acoustic or electromagnetic waves and is expressed as the ratio of power densities. Various mechanisms can give rise to attenuation. Among the most important are geometrical attenuation, absorption, and scattering.

For unconfined radiation from a point source in free space, the power density (watts per square meter) decreases in proportion to the square of the distance. The power densities, I1 and I2, at distances r1 and r2 from the source, are related by Eq. (1).

(1) 

If the signal, in a parallel beam so that there is no geometrical attenuation, passes through a lossy medium, absorption reduces the power level, I, exponentially with distance, x, according to Eq. (2), where a

(2) 
is the attenuation coefficient. See Absorption of electromagnetic radiation, Sound absorption

Scattering is said to occur if the power is not absorbed in the medium but scattered from inhomogeneities. See Scattering of electromagnetic radiation

More complicated situations occur with guided waves, such as acoustic waves in pipes or electromagnetic waves in transmission lines or waveguides, where absorption may take place and irregularities may cause reflection of some power.

In electric circuits, constituent elements are often described as attenuators when they reduce the level of signals passing through them.

Attenuation is usually measured in terms of the logarithm of the power ratio, the units being the neper or the decibel. See Decibel

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

attenuation

(ă-ten-yoo-ay -shŏn) The reduction in magnitude of a quantity as a function of distance from source or of some other parameter. The attenuation of a beam of radiation, i.e. the reduction in intensity or flux density, results from absorption and/or scattering of the waves or particles as they pass through matter.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

attenuation

[ə‚ten·yə′wā·shən]
(botany)
Tapering, sometimes to a long point.
(electricity)
The exponential decrease with distance in the amplitude of an electrical signal traveling along a very long uniform transmission line, due to conductor and dielectric losses.
(engineering)
A process by which a material is fabricated into a thin, slender configuration, such as forming a fiber from molten glass.
(microbiology)
Weakening or reduction of the virulence of a microorganism.
(physics)
The reduction in level of a quantity, such as the intensity of a wave, over an interval of a variable, such as the distance from a source.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

sound attenuation

The reduction in the intensity or in the sound pressure level of sound which is transmitted from one point to another. Also see sound insulation.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

attenuation

The decrease in the intensity of a signal, beam, or wave as a result of the absorption of energy (by the terrain or medium over which, or through which, the energy travels) and of scattering out of the path to the detector but not including the reduction as a result of geometric spreading. Attenuation is usually expressed in dB (decibles). The term is often used as a misnomer for attenuation coefficient, which is expressed in dB per kilometer.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

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 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].
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

attenuation

Loss of signal power in a transmission. Often abbreviated "ATTN."
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
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References in periodicals archive ?
Selected published attenuation relationships are used in this study.
Ground Motion Prediction Equations (GMPEs) for Pakistan: Preliminary Results
The calculated data that provides information about the thermal variation of the sound velocity and attenuation coefficient in the ordered and disordered phases and the frequency dependence of isothermal attenuation coefficient in the ordered phase of the BC model with quenched diluted crystal field will be discussed in the following.
Acoustic Signatures of the Phases and Phase Transitions in the Blume Capel Model with Random Crystal Field
In the ZPHI algorithm, [A.sub.H] is determined with a constraint that the two-way path-integrated attenuation [PIA.sub.2] is proportional to the total span of the propagation differential phase [[phi].sub.DP]:
Attenuation Correction of Weather Radar Reflectivity with Arbitrary Oriented Microwave Link
where [W.sub.[sigma]] and [W.sub.[rho]] represent the propagation attenuation factors caused by the ground conductivity ([sigma]) and Earth's curvature ([rho]), respectively.
A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges
The pipeline shock wave attenuation coefficient represented for the attenuation principle of shock wave overpressure inside the pipeline, while the branch shock wave overpressure shunt coefficient stood for the influence of the shock wave spreading inside the branch pipeline on the straight shunt effect.
Research on Gas Exploration Shock Wave Spread Law via One-Way Bifurcation Pipeline
fog attenuation prediction for optical and infrared waves," Opt.
Combined effect of turbulence and weather on radio over free space optics Ro-FSO
The attenuation produced by a dielectric material is expressed as attenuation distance or skin depth ([delta]) and is defined as the depth in the material at which the field strength decays to (1/e) i.e., 37% of its original value.
Study of attenuation of microwaves by PPy-doped PVC films
Third, the attenuation rates along all the wave paths between the source and the receiving sensors are computed.
Visualization of internal damage in RC slab with single side access attenuation tomography
In detail, the mass attenuation coefficient ([mu]/[rho]) from (2) was calculated as shown in Figure 6.
Calculation of Lead-Iron Double-Layer Thickness for Gamma-Ray Shielding by MATLAB Program
where [P.sub.G] and [P.sub.R] are the power levels received by the antennas G and R, respectively, L is the attenuation due to the vegetation, [E.sub.0i] is the amplitude of the incident electric field, and [[phi].sub.R] and [[phi].sub.G] are the phases of the incident electric field for each instrument.
Low-Cost GPS Receivers for the Monitoring of Sunflower Cover Dynamics
In order to obtain the transmission field in the time-domain, the transmission coefficient and the attenuation coefficient are represented in the time-domain.
Analytic Calculation of Transmission Field in Homogeneously Layered Mediums Excited by EMP
The attenuation of penetrated photons through unit mass per unit area of a matter is defined as the mass attenuation coefficient ([mu]/[rho]) that highly relies on the density and the atomic number of the material.
Evaluation of the attenuation values of polyethylene as a tissue equivalent of human thyroid for dosimetry purposes using single-energy and dual-energy computed tomography

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