USAGE - The NOISESTOP RAAC 43 Rectangular Duct Silencer is an absorptive baffle attenuator which converts duct borne noise energy into thermal energy within the acoustic media contained in the baffle elements. The RAAC Rectangular Duct Silencer range has been specifically designed for use in ducted ventilation and air conditioning systems. The main applications of RAAC Silencers are the reduction of mechanical noise generated by the primary air circulation fan and the elimination of secondary regenerated noise from terminal units, mixing chambers or pressure reducing devices. NOISESTOP RAAC Rectangular Duct Silencer are also used to reduce the level of external noise (aircraft, traffic etc.) entering a building, to control and contain the noise of enclosed machinery (pumps, compressors, generating sets etc.) and the elimination of speech interference, transferred be interconnecting ducting, across office walls and partitions. Selection of the correct RAAC Silencer is by subtraction of the Dynamic Insertion Loss from the source sound level with corrections being made for the natural attenuation of the duct system to obtain the established space noise criteria. NOISESTOP engineers are available on request to assist you in the proper selection of silencers foe your particular requirements.
　　　　　　　
CONSTRUCTION - The NOISESTOP RAAC 43 Rectangular Duct Silencer has inter-baffle separation of 150mm and the individual baffle elements are 200mm wide. This gives a modular width of 350mm and with this combination the silencer gives high attenuations over a short silencer length. An increase in duct cross sectional area may be required to optimize the silencer’s pressure loss and self-noise. RAAC 43 Silencers are therefore supplied with duct widths equal to any multiple of 350mm, with duct heights to suit the customer requirements and in only one of six standard lengths (900,1430,1500,1800,2100and2400mm). NOISESTOP RAAC standard Rectangular Duct Silencers are constructed from high quality galvanised sheet steel. The casings are lock-formed and conform to the latest HVCA ductwork standard. All joints are sealed with a suitable mastic sealant and the baffle elements and end flanges are retained by sealed fixings. In this standard form NOISESTOP RAAC Silencer can withstand duct static pressures up to 1250 pascals. For higher static pressures the casing of the silencer is constructed from mild steel sheet, all joints being continuously seam welded. Each silencer is normally supplied with pre-drilled mild steel end flanges and drilling details are supplied at the time of order but can be made available separately on request. Alternatively silencers can be supplied with undrilled flanges or spigot connections where required. The baffle elements contain inert, non-flammable, mineral wool retained in a galvanised sheet steel casing. The inlet profile of the baffle is aerodynamically shaped to minimize pressure losses and the side faces of the baffle are formed from stiffened perforated metal to ensure stability and integrity of the acoustic media even under adverse airflow conditions. The acoustic media can be further protected for special applications such as supplied air to clean rooms or operating theatres or extracting from kitchens, laboratories or highly contaminated industrial process areas. For such special applications a NOISESTOP engineer should be consulted to establish the most appropriate treatment.

TYPICAL SPECIFICATIONS - NOISESTOP RAAC Rectangular Duct Silencers shall be installed in the positions indicated on the drawings to maintain the acoustic criteria in the specification. The silencers shall have gelvanised sheet steel casings with frilled, mild steel, end flanges. The inlet section of the baffle elements shall be aerodynamically shaped. The acoustic media shall be inert, non-flammable mineral wool. The acoustic media shall be retained in position by perforated, galvanised steel face sheets stiffened to maintain the integrity of the baffle element even under adverse airflow conditions