Rectangular Attenuators SagiCofim To know noise The control of noise level in a room is now a very frequent requirement to allow carrying out normal activities in a comfortable way. Its extent depends on the type of room and on the activities being carried out therein; design acoustic conditions are different according to whether reference is made, for instance, to a hospitalisation room or a restaurant. Typical sound level varies according to the type of room and, similarly, sound control requirements are different. Air-conditioning systems include a number of sound sources able to introduce...

Rectangular Attenuators SagiCofim Sound pressure level, Lp Differently from sound power level, sound pressure level (Lp) can be affected through a lot of external factors: the distance between source and instrument, the presence or absence of reflecting surfaces in the proximity of the source, the presence of barriers or obstacles along the path etc. Therefore, it undergoes variations depending on the conditions in which measurement has been carried out. In a free field, sound pressure level is reduced by6dB per each distance doubling. In normal civil rooms this reduction ranges from 3 to 4 dB....

Rectangular Attenuators SagiCofim Features RAS series attenuators are products with top level acoustic performances, great manufacturing features and low pressure drops; all models have currently aerodynamic profiles on the splitters to limit the resistance to the air flow and the regeneration of noise as much as possible. Acoustic insulation panels are made of mineral fibre with high acoustic absorption features; in the standard version they are coated with a sheet of reinforced glass. Furthermore, the RAS-LF version is made with splitters protected by perforated sheet. Splitters are set inside...

Rectangular Attenuators SagiCofim Table 3a- Loss of Static Insertion Mod. RAS-A - Module 300 mm Table 3 b - Loss of Static Insertion Mod. RAS-L - Module 350 mm Table 3 c - Loss of Static Insertion Mod. RAS-M - Module 400 mm The values of aerodynamic factors refer to the attenuators installed according to ASTM E477-80 IHints for the choice of attenuators 1 Choose the type of attenuator and the relevant code in tables 3 (a, b, c) according to the acoustic performances required. Each model is available in lengths ranging from 600 to 2400 m. 2 Identify, in the nearby table, the aerodynamic "K"factor corresponding...

Rectangular Attenuators SagiCofim Chart 1 Front speed in function of the pressure drop and of the aerodynamic factor Table 4 Noise self-generated by the attenuator NC or RC models due to noise regeneration Models RAS-A RAS-L RAS-M

Rectangular Attenuators SagiCofim Chart 2 (a) - model RAS A Cross section of the attenuator Width Height (mm) (mm) 1500 x 1800 1500 x 1650 1500 x 1500 1500 x 1350 1200 x 1500 1200 x 1350 1200 x 1200 900 x 1500 900 x 1350 900 x 1200 900 x 1050 900 x 900 900 x 750 600 x 1050 600 x 900 600 x 750 600 x 600

Rectangular Attenuators Cross section of the attenuator

Rectangular Attenuators SagiCofim Chart 2 (c) - model RAS M Cross section of the attenuator Width Height (mm) (mm) 1600 x 1650 1600 x 1500 1600 x 1350 1200 x 1650 1200 x 1500 1200 x 1350 1200 x 1200 1200 x 1050 1200 x 900 800 x 1200 800 x 1050 800 x 900 800 x 750

Rectangular Attenuators SagiCofim Table 6 Noise correction by additional Self-generated noise Attenuators generate noise due to the air flowing through them, to the turbulent fluxes and to pressure fluctuations. The bigger is the air flow rate, the bigger is the regenerated noise, due tothe increased cross speed. Chart 3 shows the levels ofthe noise coming out ofan attenuator, in function ofcross speed. To calculate such speed it is necessary to find out front speed in Charts (a, b or c). Such value is to be multiplied by the corresponding factor in the table. Table 5 To define cross speed, multiply...

Rectangular Attenuators SagiCofim The note at the foot ofeach table sets forth the expression to calculate the weight ofthe perforated sheet, if any, to add to standard weight. Standard weight of attenuators in Kg Perforated sheet weight = 21xLxBxH (kg)

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