Reduce the acoustic level of adjustable ventilation grilles

The problem of noise in ducts and ventilation grilles

It should be noted that ventilation systems can be a source of impact noise, due to the vibrations of the ducting, and airborne noise, due to changes in the air flow rate. Consequently, the particularities of the system should be evaluated and a differentiation should be made between the noise produced in straight sections, the noise produced in junctions, and the noise that occurs at the various air outlets (grilles and diffusers).

Due to the problem of noise, both the grilles and the entire ventilation system must be designed with special care. In addition, it should be taken into account that in the case of noise from the system, its magnitude increases at mid frequencies. In general, the sound level at low frequencies is mainly affected by the volume of air circulating through the grille and its size.

In the case of adjustable ventilation grilles, noise is affected by their opening. Higher frequencies will depend on the speed of air circulation through the grille and the pressure loss that it provides.

If there is a flow control valve just before a grille, noise increases depending on the degree of opening. Thus, a valve opened 50% increases the noise level by about 16 decibels. An appropriate valve that offers high protection against noise, even when fully open, will not increase the noise level produced by the grille.

Noise produced in straight sections formed by metal ducts and diffusers

Like other elements of the ventilation system, information about the noise generated in the ducting (straight ducts, junctions, and diffusers) can be provided by the manufacturer, depending on the speed of the air flow and the section of the ducts that make up the system.

Noise protection for ducting and adjustable ventilation grilles

A good installation assembly is the first step to prevent both the production and transmission of noise. Thus, it is advisable to avoid rigid joints between the ducts and their respective mounting points. The use of grilles and ducts lined with absorbent material will also be important. Finally, the installation should be properly sized to adjust the section of the entire ducting to the air flow circulating through it and reduce the air speed.

The effects of noise produced by the grilles of ventilation systems can be reduced if they are installed in rooms considering the distribution of sound within the space. Thus, it will be ensured that the grilles are not placed in the corners of the rooms and are installed, as much as possible, in the center of the ceiling.