Anechoic, semi anechoic and reverberating chambers are defined as auxiliary items to standardized measurement systems. Such chambers are environments where noise data acquisitions are carried out through suitable instruments.

Chambers efficiency will be achieved through following critical requirements:

- Complete insulation from any type of noise, vibration and disturbance coming from external environment;
Absorption (for anechoic and semi anechoic) or ambient returning (for reverberating) capacity for all internal-produced noises and disturbances.

Regardless from chamber type, these environments will be structured by materials, whose succession determines noise and vibrations insulation; and internal finishing, strictly connected with required features.

Therefore, a measurement chamber must be composed of:

An External cortex, capable of efficient noise insulation. Insulation will be functional to several requisitions: the surrounding area noise level; casual events, potentially occuring and capable of measurements alterations; a specific, quantified requested insulation ratio (Rw);
An Internal finish, to simulate noise datas with normal working conditions (that is, not at laboratory conditions) on tested apparatus. This feature is different according to the designed ambient:

o The anechoic chamber features completely noise absorbing walls, roof and floor; walls noise absorption capacity is defined by cut frequency (that is the frequency beyond which there will be complete absorption) and reverberating time (that is walls capacity to determine the reduction of sound pressure for 60 dB(A), once noise source activity is stopped, in the least time).

o The semi-anechoic chamber does not necessarily features all walls or floor with complete noise absorbing capacity. For this reason the chamber will be used to test products, machineries or systems simulating their operational behaviour.
Some example: car testings make no sense into an anechoic chamber, since cars will always work on a noise-reflecting surface, that is road surface. At the same time, household appliances will be most likely installed close to concrete, noise reflecting walls. Therefore, such test ambients will feature strongly noise refelcting floor/wall.

o The reverberating chamber is normally used when linked to one of the previously described ambients (“matched cells” configuration). Its purpose is to perform noise insulation measurements on materials interponed between cells. Inside the chamber, an intense noise pressure will be produced; this pressure will tend to remain constant due to strong reflection ambient feature. In the matched cell will be measured a cells-interponed product capacity to eliminate signal transmission through aerial channel. Performances will be measured by all-frequencies insulation mapping.

Anechoic Chamber.
Semi-anechoic Chamber.
Semi-anechoic Chamber with Control Room.
Control room side view.
"Combi" door frame, featuring 6 seals.
"Combi" door, featuring 60 dB RW - detail.
Pre-compressed, prefabricated external cortex.
Slab disjoining works - detail.
Burnt gases suction system - reel.
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