Thermal comfort and air renewal are fundamental features for a building (whether residential, tertiary or industrial) requiring a Heating Ventilation and Air-Conditioning (HVAC) installation often involving air flows that are often rejected outside, and therefore, if they themselves constitute a source of flow noise e.g. because of excessive fluid speeds or if they allow the propagation of noise of upstream components, may be in able to negatively impact the sound environment, especially in the case of night-time operation, during which the residual noise level is generally the lowest: the tranquility of residents is then the issue.

An Air Handling Unit (AHU) is a main component of such an installation (with fan, hot or cold battery, filter) allowing to have inside a building an air whose temperature and hygrometry are controlled (often it is a supply of fresh air, which purified): it is often installed outside the buildings it serves.

ITS participated in the reduction of noise emissions from an Air Handling Unit (AHU), part of a Heating Ventilation and Air-Conditioning (HVAC) installation in the Lyon area (Auvergne-Rhône-Alpes region, France).

The aim was to limit the noise emitted by the rejection of the ventilation network of an air conditioning installation located on the roof of a building on a university campus, for which an acoustic study had previously revealed that authorized sound levels were exceeded.

For ITS it was necessary to study a silencer capable of attenuating the discharge noise of the Air Handling Unit, while producing only a very small total pressure loss, compatible with that resulting from the dimensioning (well before) of the installation, and while respecting very restrictive dimensional limits, in relation to a limited space available between the exit orifice and the edge of the roof of the building (a cantilever installation beyond the acroterium being proscribed).

In this case, ITS used a design based on the use of resonant separators, the only one able to offer the required performance in terms of insertion loss (low, medium and high frequency) with the necessary compactness for the silencer, whose choice of cross-section was the subject of particular attention to satisfy the conflicting criteria of a negligible pressure drop and a sufficiently low noise level, while allowing a connection to the discharge port of the unit with sufficiently short transition pieces.

A supporting structure, a rain protection and an anti-bird scree were part (as often) of the soundproofing system which was built and installed following this careful engineering work in acoustics and aerodynamics: the neighbors of this installation will be able to sleep peacefully again.