Absorption (acoustics)

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Absorption (acoustics)

Absorption refers to the absorption of sound waves

Sound

Sound is vibration transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a threshold of hearing to be heard, or the sensation stimulated in organs of hearing by such vibrations....
by a material. The absorption is the "missing piece", when comparing the total reflected and transmitted energy with the incident energy.

It is the property of a material that changes acoustic energy into usually heat energy. A material or surface that absorbs sound waves does not reflect them. Absorption of a given material is frequency-dependent and is affected by the size, shape, location, and mounting method used.

A good sound absorber is normally a porous material.

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Encyclopedia

Absorption refers to the absorption of sound waves

Sound

Mineral wool

Mineral wool, also known as mineral fibers or man-made mineral fibers are fibers made from natural or synthetic minerals or metal oxides....
, glass wool

Glass wool

Glass wool is a form of fibreglass where very thin strands of glass are arranged into a spongy texture similar to steel wool. Glass wool is used widely as an Thermal insulation material....
, and micro perforated plate

Micro perforated plate

A Micro Perforated Plate is a device used to absorb sound, reducing its intensity. It consists of a thin flat plate, made from one of several different materials, with small holes punched in it....
s work as sound absorbers.

Absorption is not a single mechanism of sound attenuation

Attenuation

In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, and X-rays are attenuated by lead....
. Propagation through a heterogeneous

Heterogeneous

Heterogeneous is an adjective used to describe an object or system consisting of multiple items having a large number of structural variations. It is the opposite of homogeneous, which means that an object or system consists of multiple identical items....
system is affected by scattering

Scattering

Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles,are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass....
as well.

Acoustical absorption is represented with the symbol A.

Acoustical absorption in the ocean is an important part of the analysis of Sonar. The primary substance in seawater that is responsible for absorption is Magnesium sulfate

Magnesium sulfate

Magnesium sulfate is a chemical compound containing magnesium and sulfate, with the formula MgSO4. In its hydrated form the pH is 6.0 ....
. The secondary substance is boric acid

Boric acid

Boric acid, also called boracic acid or orthoboric acid or Acidum Boricum, is a weak acid often used as an antiseptic, insecticide, flame retardant, in nuclear power plants to control the fission rate of uranium, and as a precursor of other chemical compounds....
. The most common sea salt, sodium chloride

Sodium chloride

Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the chemical formula SodiumChlorine....
has virtually zero effect on sound absorption.

Absorption (acoustics)

See also