ITS intervenes for the development of testing / acoustic measurement rooms, often in the context of research and development (R&D) projects in acoustics e.g. anechoic rooms & semi-anechoic rooms, aeroacoustic wind tunnels.

The objective is often to obtain in a closed space acoustic conditions in a free field, generally observable outside - when there is then no limit to the propagation of sound - which requires for the walls, the roof (and, in the case of a fully anechoic room, also for the floor) the implementation of a sound-absorbing lining, capable of avoiding the reflections of acoustic waves in a frequency band of interest (sometimes very large: from a few tens of Hz to several tens of kiloHertz) corresponding to the (variable) needs of users in terms of metrology.

Conventional wedges (i.e. blocks of foam or mineral wool or polyester), pyramid-shaped (with or without cover and/or perforated protection) constitute a common soundproofing lining, having proven its worth in multiple occasions, but which is not ideal in various contexts:

  • when it comes to low frequency performance (e.g. when the cutoff frequency is as small as 100 Hz), since the thickness required to obtain a sound absorption coefficient of 100% (as measured for a normal incidence in a Kundt tube), being approximately 1/4 of the longest wavelength to be considered (not far from a meter), can become a serious obstacle to obtaining sufficient space for the installation of the noise source under test and (taking into account the required distances) the microphones in its environment; the problem arises in particular in the case of a retrofit of a room for which a lower cut-off frequency is desired (i.e. for better performance than what exists)
  • when it comes to the experiment room of a high speed wind tunnel, because the unevenness of the walls can create turbulence inducing unwanted noise

Compact broadband absorbers (multilayered, with a membrane in the rear part intended for the absorption of low frequencies) then constitute an efficient means of obtaining an acoustic test / measurement room in accordance with the requirements of the standards in force, in relationship with a specific metrology [1] [2] [3]; porous absorbers with an asymmetric structure are also part of the devices marketed by ITS.

Sometimes, the aim is to obtain, inside the acoustic test / measurement room, a sufficiently low background noise level (of the order of 20 dB per 1/3 band octave, including for low frequencies), for which a particularly high sound reduction may be necessary (sometimes: greater than 60 dB at some frequencies) - for the walls, the roof (and, in the event of a room also fully anechoic, for the flooring, then having to be decoupled from its support to limit vibro-acoustic transmissions) - constituting the envelope, the functionality of which is to reduce the transmission of external noise.

A masonry construction of this envelope is often associated with this requirement, but does not have all the advantages of the alternative that a metal construction with a steel frame and modular acoustic insulation panels is:

  • lower weight footprint (the place of installation of an acoustic test / measurement room is not always chosen on the basis of its capacity to accept the overload inherent in the use of materials with surface masses as large as those of common thickness concrete walls and slabs)
  • possibility of dismantling and reuse of the testing equipment (e.g. according to reorganizations and relocations of competence centers)

In the case of test benches (e.g. engines test rigs), the sound power level of the sound source being tested (often: above 125 dB) imposes, for the walls:

  • sound absorption properties, to limit the amplification of sound levels due to reverberation, which would otherwise - all other things being equal - increase outside sound levels
  • an ability to limit the transmission of noise towards the outside, in areas that must be protected:
    • within the perimeter of the establishment in which the test bench is installed (e.g. for employees, working on post or traveling nearbywith - with, depending on the context, a concern relating to the reduction of exposure to noise to avoid hearing trauma or to the quality of the sound environment for the accomplishment of tasks by company employees, whether or not they require a particular concentration)
    • outside the site: so as not to disturb the neighbors

Industrial soundproofing panels such as those marketed by ITS (offering the advantages mentioned above with regard to metallic sound insulation panels for the construction of acoustic testing / measurement rooms, and incorporating - then necessarily - a layer intended for sound absorption on the side of the noise source that the hardware under test is), are suitable for such realizations.

Of course, whether it is a test room / acoustic measurements, or a test bench, the treatment of openings (access with soundproof door sets, ventilation apertures with silencers and noise reduction devices for fans) is a key point for the success of a project, as is the ability to integrate the other required functions (depending on the context: in terms of electricity, lighting, fire safety, air conditioning, flue gas exhaust) which requires an experience which is not lacking in the human resource of ITS.

[1] ISO 3744:2010 Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane

[2] ISO 3745:2012 Acoustics — Determination of sound power levels and sound energy levels of noise sources using sound pressure — Precision methods for anechoic rooms and hemi-anechoic rooms

[3] ISO 26101-1:2021 Acoustics — Test methods for the qualification of the acoustic environment — Part 1: Qualification of free-field environments

Products & solutions: systems

A

Acoustic laboratory
Acoustic measurement room
Acoustic testing room
Acoustical insulation system for test benches
Aeroacoustic wind tunnel
Anechoic chamber
Anechoic room

D

Dead room

N

Noise diminution device for test benches
Noise limitation device for test benches
Noise reduction device for test benches

S

Sound attenuator for test benches
Soundproof listening room (for test jury)
Soundproofed test bench
Soundproofing system for test benches

Products & solutions: components

A

Absorbing lining for acoustic laboratories
Absorbing lining for acoustic measurement rooms
Absorbing lining for anechoic chambers
Absorbing lining for anechoic rooms
Absorbing lining for dead rooms
Absorbing lining for measurement in a free acoustic field
Absorbing lining for test benches
Absorbing material for acoustic laboratories
Absorbing material for acoustic measurement rooms
Absorbing material for anechoic chambers
Absorbing material for anechoic rooms
Absorbing material for dead rooms
Absorbing material for measurement in a free acoustic field
Absorbing material for test benches
Absorbing wedge for acoustic laboratories
Absorbing wedge for acoustic measurement rooms
Absorbing wedge for anechoic chambers
Absorbing wedge for anechoic rooms
Absorbing wedge for dead rooms
Absorbing wedge for measurement in a free acoustic field

Frequently asked questions

Frequently asked questions

end faq