Acoustic attenuators

Emtec RAAC silencers consist of an absorptive baffle attenuator which converts duct-borne noise energy into thermal energy within the acoustic media contained in the baffle elements.
The main applications of Emtec RAAC silencers are:

Reduction of duct-borne mechanical noise generated by the primary air circulation fan
Elimination of secondary regenerated noise from terminal units, mixing chambers or pressure reducing devices
Reduction of internal noise break-out from plant rooms and noisy spaces
Reduction of external noise break-in to noise sensitive spaces

Performance
The extensive Emtec RAAC rectangular silencer range has been specifically designed for use in ducted ventilation and air conditioning systems, however the casing and flanges are easily engineered to other applications. For instance, building into ventilation apertures formed within the Walls or roof of a plant room.
And we know about weather louvres. So can provide complete weathering and noise control services for the building envelope. Along with cladding and Screening services for external plant.
In addition to the above, the data sheets provide more detailed information.