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Please find below a Glossary of Terms relating to Acoustic Cleaning which we have compiled for the benefit of all those interested in understanding the principles of the science and its associated, often industry-related terminology.


The removal or erosion of material from the surface of a solid due to friction imparted by the movement of another gas, liquid or solid.


The science of sound, including its production, transmission and effects


The state in which two materials are held together by forces existing between the surfaces.


The adherence of one substance on the surface of another.


A technique that combines small or powdered materials into larger particles, sub-clusters and clusters.

Airborne sound

Sound transmitted through air as a medium rather than through solids or the structure of a building

Ambient Noise

The background noise in an area, generally measured without noise of particular interest


A space which is almost totally free of reflection over a wide range of frequencies. An anechoic chamber gives close to free field conditions.

Background level

The normal sound level present in an area.

Bag filter

Process plant containing one or more cloth bags for recovering or removing particles from dust laden gas or air.


A process in which two or more materials are mixed together so the parts are intermingled with one another.


A high temperature water heater used for the generation of steam or cooling of gasses.


The process of making beer, ale or other malt beverages by boiling mashed malt to produce a wort, flavoring with hops, fermenting this mixture with yeast, and drawing off the fermented wort for distribution in barrels or bottles.

Carbon Black

Carbon black is a powdered form of carbon. It is used for its mechanical properties and pigmentation effects in many automotive products as well as rubbers inks and dyes.


A powder made from silica, alumina, lime, iron oxide, and magnesia which solidifies when mixed with water; this is used as an ingredient in mortar, concrete self levelling solutions etc.


Solid materials made by firing of non-metallic minerals, used in the manufacture of such products as tile, plaster refractories or brick.


A process in which a substance of individual particles comes together to form a coherent mass.


The act or process of pressing together substances either through gravity or applied pressure, which can form a denser substance or cohesive product.


The transfer of heat by molecular collision. This process is more efficient in metals and other thermal conductors and poorer when combustion products build up on heat exchange surfaces.


A device designed to regulate the fuel, air, water, steam, or electrical supply to the controlled equipment. It may be automatic, semi-automatic or manual.


The addition of some unwanted substance to a product or intended mixture of products.


Removal of kinetic energy in an oscillating medium by converting it to heat using frictional or viscous forces.


A division of a uniform scale based upon 10 times the logarithm to the base ten of the ratio of sound field intensities being compared

Diffuse sound field

A sound field in which the energy density is the same everywhere and sound waves are likely to be travelling in any direction with equal probability.


Concentration of acoustic energy within a limited location in a room as the result of reflections from concave surfaces.

Free field

A region in which no significant reflection of sound happens

Fundamental frequency

The frequency with which a periodic function reproduces itself.


An enclosed chamber where high temperature reactions or combustion take place.


The process of converting solid or liquid products into a gaseous fuel through heating in the absence or reduced presence of oxygen.


Calcium sulfate dihysrate, CaS04.2H2O, used in wallboard manufacture, and fertilizers.


A sinusoidal component in a complex periodic wave of frequency, which is an integral multiple of the fundamental frequency of the wave.


A substance that absorbs moisture from the air.

Induced draft fan

A fan which pulls a gas or air stream usually used for high temperature gasses. .


The rate of sound energy transmitted in a specified direction through a unit area

Kiln Dust

Dust produced during cement or lime processing.


A covering, usually of insulating material, on pipe or ductsLoudness
The subjective judgement of the intensity of a sound.

Natural frequency

The frequency at which a resiliently mounted mass when set into vibration would vibrate under the influence of gravity alone with no additional forces or constraints.


Solids that reflect light of certain wavelengths, without producing appreciable luminescence these are used in solids and paints to achieve a desired colour.


Chains of molecules formed by the chemical combination of two or more identical combining units called monomers.


Materials suitable for use at high temperatures; usually used for thermal insulating or thermal barriers composed of aluminas, silicas, etc.


The persistence of sound within a space after the source has ceased, due to repeated reflections at the boundaries of the space (walls)

Reverberation time

The time it takes for a reverberant sound of a given frequency to decay by 60dB after the source is cut off.


A means of converting Nox gasses (nitrogen oxides) with the aid of a catalyst into Nitrogen and water. SCR's use ammonia as the reducing agent. This prevents Nox gasses entering the atmosphere where they can combine with cloud moisture to produce the strong inorganic acid – Nitric Acid.

Slag cements

Cements made from blast furnace slag.

Sound Power Level (SPL)

A value equal to 10 times the logarithm to the base 10 of the ratio of total acoustic power emitted by a source to a reference pressure normally 2 x 105 N/m2.

Spray Drying

The production of a solid product by the atomization of a liquid solution into a heated vessel which evaporates the liquid. The dry particles fall to the bottom of the vessel.

White Noise

Noise of a statistically random nature having equal energy at every frequency between set limits.

Wood Pulp

Wood which has been broken down, to a fine powdered substance called pulp through mechanical or chemical processes.