Install a silencer and comply with acoustic regulatory levels

Current regulations (CTE DB HR, Protection against noise and RITE ) emphasize the importance of protecting ourselves from acoustic pollution. The purpose is to minimize the nuisances and ailments that noise can cause to the occupants of a building. Thus, the CTE DB HR, Protection against noise establishes guidelines for its design, use, and maintenance, so that it is ensured that the constructive elements that make it up have appropriate acoustic properties. These characteristics should aim to minimize the transmission of the following types of noise: airborne noise, reverberant noise, noise due to impacts, and noise coming from the facilities of the premises. The RITE, Regulation of thermal installations in buildings, also emphasizes this issue, highlighting the importance of the silencer in ventilation systems.

Obligations of the supplying companies

The RITE establishes the obligations of supplying companies of the elements that make up the air conditioning and ventilation systems regarding noise. In this way, companies must provide the following documentation:

• Acoustic power level of the equipment that produces stationary noises (these mainly come from air conditioning units -pumps, fans, etc.-).

• The mechanical rigidity and the maximum load of the elastic beds used in inertia benches.

• The noise mitigation effect (damping), transmissibility, and the maximum load of the antivibratory systems.

• The noise absorption factor of the absorbent products used in the ventilation ducts.

• The mitigation of the prefabricated ducts.

• The total attenuation of the silencers (installed in ducts or embedded in the envelope).

Installation of a silencer in the ventilation system

The regulation, which also states that the acoustic power level of the equipment located outside cannot exceed 70 dB, specifies that a silencer must be installed in the smoke outlets of the premises. This affects, according to the document, the air intake or extraction grids of a machine room or air treatment units (or air conditioners). It should be noted that silencers should not be installed in the smoke outlets of laboratories, kitchens, or boilers, given the high risk of contamination.

The sound-absorbing material of the silencers must be coated with a material that can prevent them from getting dirty and allow the internal sanitization of the silencer, without reducing the qualities of that sound-absorbing material.

The extraction ducts of the systems must be insulated so that the acoustic reduction rate is, at a minimum, 33 dBA. In the case of smoke extraction systems in parking buildings, it must be 45 dBA.

The regulation also states that the installation of ducts (for both ventilation and air conditioning) must be insulated from the noise inevitably generated by the system fans and the air circulation itself. Therefore, the inside of the ducts should be lined with absorbent material, or that attenuates acoustic pollution (mitigation must be greater than 40 dB). In sheet metal ducts, the use of inner linings should be avoided.