Noise level is calculated at the design stage. A competent designer will immediately select equipment with a reduced noise level. So, the fan should be with a low number of revolutions, but it must be able to move the specified amount of air, as well as create the necessary pressure.
For example, instead of four -pole engines of fans operating at a speed of one and a half thousand rpm, usually six -pole, having 960 rpm, but with less noise. Be sure to take into account the noise on the suction of the fan, the noise on the emission and the noise transmitted through the case. To reduce noise in the channels, noise -lodgers are placed on both suction and fan emissions.
To reduce the noise transmitted through the body, fans are used in soundproof design and organized soundproofing ventilations. Vybrovtvs are well saved from strong vibration, as well as, of course, soft inserts. Unfortunately, now there are not enough good specialists who know acoustic calculations, and it happens that the ventilation system has already been designed, but because of the mistake made, it is very noisy. In this case, it is necessary to reduce the number of turns of the fan, if it is possible to reduce the number of displaced air. And when it is unacceptable, for example in pools, you have to change equipment, expand the supply and exhaust channels.
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