lindab | acoustic solutions Rectangular curved silencer BDLD Manual designing for BDLD A number of silencers can be designed manually, for more combinations of silencers and faster calculations use DIMsilencer. 1 Manual method of calculation is shown below: 2 A Width Specify connection dimensions and flow-type location of the silencer. 800 mm Heigh 1000 mm Leg lengh 150 mm 3 Location Exhaust air BDLD-800-1000-150-3008 4 B Specify the sound power level before the silencer. 5 Read the insertion attenuation from the tables on page 80 – 82. 6 Calculate the sound power level after the silencer irrespective of the air flow (selv generated noise). Insertion attenuation 7 63 Hz 125 Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz 8000Hz Resistance number Self generated noise number inlet 8 Sound power level 72 73 73 64 62 59 52 44 before silencer Attenuation from 3 10 17 17 16 16 17 17 1,8 1,6 table page 80 – 82 9 Sound power level after silencer without 69 63 56 47 46 43 35 27 self generated noise 10 C Determine the pressure drop with help of the graph on page 77 and table on page 78. 11 In this case we have straight ducts before and after the silencer. Pressure drop Area 0,8 m² Air flow 400 l/s 12 Graph on page 77, use resistance number, area and air velocity Air velocity 5 m/s Pressure drop 28 Pa Correction at disturbance according table on page 78 Factor 1 Pressure drop 28 Pa after correction 13 14 D Determine the self generated noise from the silencer at present air flow. Calculate the sound power level after the silencer inclusive the self generated noise. Self generated noise 63 Hz 125 Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz 8000Hz 15 16 Graph on page 79, use resistance number 59 56 49 46 44 40 36 28 and air velocity Correction for gross cross section area -1 -1 -1 -1 -1 -1 -1 -1 Self generated noise 58 55 48 45 43 39 35 27 17 Sound power level after the silencer 69 64 57 49 48 44 38 30 (Logarithmical addition of self generated noise and sound power level after the silencer without self generated noise) 18 We reserve the right to make changes without prior notice 75 2017-12-11
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