lindab | acoustic solutions Rectangular straight silencer DLD/DLDR Manual designing for DLD and DLDR A number of silencers can be designed manually, for more combinations of silencers and faster calculations use DIMsilencer. Manual method of calculation is shown below: A Specify connection dimensions and flow-type location of the silencer. Width Heigh Length Location 800 mm 1000 mm 1250 mm Exhaust air DLD-800-1000-1250-1016 B Specify the sound power level before the silencer. Read the insertion attenuation from the tables on page 42 – 45. Calculate the sound power level after the silencer irrespective of the air flow (selv generated noise). Insertion attenuation Sound power level before silencer Attenuation from table page 42 – 45 Sound power level after silencer without self generated noise 63 Hz 125 Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz 8000Hz Resistance number Self gene- rated noise number inlet 72 73 73 64 62 59 52 44 3 9 16 23 23 17 12 9 2,8 2,7 69 64 57 41 39 42 40 35 C Determine the pressure drop with help of the graph on page 39 and table on page 40. In this case we have straight ducts before and after the silencer. Pressure drop Graph on page 39, use resistance number, area and air velocity Correction at disturbance according table on page 40 Area Air velocity Factor 0,8 m² 5 m/s 1 Air flow Pressure drop Pressure drop after correction 400 l/s 42 Pa 42 Pa 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 Graph on page 41, use resistance number 59 55 54 51 48 45 41 35 and air velocity Correction for gross cross section area -1 -1 -1 -1 -1 -1 -1 -1 Self generated noise 58 54 53 50 47 44 40 34 Sound power level after the silencer 69 64 58 51 48 46 43 38 (Logarithmical addition of self generated noise and sound power level after the silencer without self generated noise) We reserve the right to make changes without prior notice 37 2017-12-11
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