Sponsored Links
Sound power level attenuation in elbows is based on sound reflection. Only in big ducts and at high frequencies is the attenuation considerable.

Attenuation in ducts at different sizes and at different frequencies for some common configurations can be taken from the table below.
| Attenuation (dB) |
Width B (mm) |
Octave band center frequency Hz | ||||||
| 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | ||
| Duct without insulation | 125 | 0 | 0 | 0 | 6 | 8 | 4 | 3 |
| 250 | 0 | 0 | 6 | 8 | 4 | 3 | 3 | |
| 500 | 0 | 6 | 8 | 4 | 3 | 3 | 3 | |
| 1000 | 6 | 8 | 4 | 3 | 3 | 3 | 3 | |
| Insulation in front of elbow | 125 | 0 | 0 | 0 | 6 | 8 | 6 | 8 |
| 250 | 0 | 0 | 6 | 8 | 6 | 8 | 11 | |
| 500 | 0 | 6 | 8 | 6 | 8 | 11 | 11 | |
| 1000 | 6 | 8 | 6 | 8 | 11 | 11 | 11 | |
| Insulation after the elbow | 125 | 0 | 0 | 0 | 7 | 11 | 10 | 10 |
| 250 | 0 | 0 | 7 | 11 | 10 | 10 | 10 | |
| 500 | 0 | 7 | 11 | 10 | 10 | 10 | 10 | |
| 1000 | 7 | 11 | 10 | 10 | 10 | 10 | 10 | |
| Insulation in front and after the elbow | 125 | 0 | 0 | 0 | 7 | 12 | 14 | 16 |
| 250 | 0 | 0 | 7 | 12 | 14 | 16 | 18 | |
| 500 | 0 | 7 | 12 | 14 | 16 | 18 | 18 | |
| 1000 | 7 | 12 | 14 | 16 | 18 | 18 | 18 | |
Sponsored Links
Sponsored Links
Free SketchUp Engineering ToolBox - enabled for use with the amazing, fun and free Google SketchUp.
© The Engineering ToolBox 2005
8 6 27