absorber
- Absorbers
used in acoustics
The term absorbers or sound absorbers is used in acoustics. They are devices installed in a room that absorb sound energy and convert it into another form of energy, such as deformation energy or heat. The materials used for absorbers have a high absorption coefficient, and acoustic absorption is frequency-dependent. Therefore, in addition to absorbers that are strongly frequency-dependent, there are also those with which broadband absorption is possible. These include porous and perforated boards, mineral fibers, foams, curtains, carpets, glass and rock wool. They are particularly efficient when the air movement is the fastest, that is, the sound velocity is the greatest. When installing absorbers, it is important to consider the frequencies that are to experience sound attenuation, since the distances between the reflecting walls and the absorbers has an influence on the wavelength to be attenuated. The German Institute for Standardization e.V.(DIN) has divided sound absorbers into sound absorption classes. According to DIN 11654, which also exists as an ENstandard and an ISO standard, sound absorbers are divided into five absorption classes. Absorbers are used not only in theaters, concert halls and conference rooms, but also in fully anechoic chambers( FAC) and semi-anechoic chambers ( SAC). In addition, DIN 18041 provides a basis for acoustic quality in medium-sized rooms. This standard deals with the technical details for the installation of absorbing and reflecting elements to improve speech intelligibility. - Absorbers
used in RF technology
Absorbers are also used in radar, radio frequency and microwave technology as well as in EMC measurement rooms. The walls, ceilings and floors of the measurement rooms are lined with the RF absorbers and absorb high-frequency vibrations. The absorbers used in RF technology and microwave engineering are pyramid or cone-shaped and have a length of up to 2.5 meters. They consist of lossy dielectrics or ferromagnetic materials that absorb RF energy and convert it into heat. The absorber plates, known as ferrite tiles, can be used up to frequencies of 1.5 GHz. In the microwave range, microwave absorbers are used up to frequencies of 100 GHz. These are foam absorbers that absorb microwaves.
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