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Attenuation

In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates.

This article is about attenuation in physics. For other uses, see Attenuation (disambiguation).

Hearing protectors help reduce acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs).


In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field.

Ultrasound attenuation measurement in systems, like emulsions or colloids, yields information on particle size distribution. There is an ISO standard on this technique.[3]

heterogeneous

Ultrasound attenuation can be used for measurement. There are acoustic rheometers that employ Stokes' law for measuring extensional viscosity and volume viscosity.

extensional rheology

geometric dispersion caused by distribution of the seismic energy to greater volumes

dispersion as heat, also called intrinsic attenuation or anelastic attenuation.

The energy with which an earthquake affects a location depends on the running distance. The attenuation in the signal of ground motion intensity plays an important role in the assessment of possible strong groundshaking. A seismic wave loses energy as it propagates through the earth (seismic attenuation). This phenomenon is tied into the dispersion of the seismic energy with the distance. There are two types of dissipated energy:


In porous fluid—saturated sedimentary rocks such as sandstones, intrinsic attenuation of seismic waves is primarily caused by the wave-induced flow of the pore fluid relative to the solid frame. [12][13]

At the electronic level, it depends on whether the electron orbitals are spaced (or "quantized") such that they can absorb a quantum of light (or photon) of a specific wavelength or frequency in the ultraviolet (UV) or visible ranges. This is what gives rise to color.

At the atomic or molecular level, it depends on the frequencies of atomic or molecular vibrations or chemical bonds, how close-packed its atoms or molecules are, and whether or not the atoms or molecules exhibit long-range order. These factors will determine the capacity of the material transmitting longer wavelengths in the infrared (IR), far IR, radio and microwave ranges.

NIST's XAAMDI: X-Ray Attenuation and Absorption for Materials of Dosimetric Interest Database

NIST's XCOM: Photon Cross Sections Database

NIST's FAST: Attenuation and Scattering Tables

Underwater Radio Communication