Elbow Silencers

Pressure Drop

The expected static or total pressure drop across the silencer allowing for adequate pressure recovery, when silencers are mounted close to fans, downstream elbows, etc., pressure drop corrections are required. These can be obtained from the guideline chart.

Insertion Loss

The decrease in noise level due to the insertion of the silencer into the duct system.

Silencer Length = Length Along Centerline = A+B = C+D

Selection Procedure: (when W1=W2)

If Elbow Size is Known:

• Step 1. Establish dimensions A, B, C, D, W1 and W2

• Step 2. Calculate approach velocity to silencer

• Step 3. Calculate silencer length; length along centerline equals A+B = C + D; when W1 = W2

• Step 4. Using W1, establish a set of possible module widths where;

  • X = (W/No. of Modules) ≤ 24" (610mm)

• Step 5. Establish your Insertion Loss(IL) and change in pressure criteria

• Step 6. Using the accompanying "Acoustic & Pressure Drop Ratings" chart, select the largest member of the module width set that satisfies both IL and chang in pressure criteria

• Step 7. If no module seems able to satisfy your IL criterion within the specified pressure drop (change in pressure), alter the W1 and/or "H" values of your approach ductwork to reduce approach velocity

• Step 8. Repeat steps 1 thru 6

If Elbow Size is Unknown:

• Step 1. Establish your Insertion Loss(IL), change in pressure and approach velocity criteria

• Step 2. Using the accompanying "Acoustic & Pressure Drop Ratings" chart, select the largest module size that satisfies your criteria

• Step 3. Establish dimensions A, B, C, D, W1 and W2 to suit the space available

• Step 4. If step 3 seems impossible:

  • (a) Alter your change in pressure and/or approach velocity

  • (b) Repeat steps 1 thru 4

Elbow Modules
Module	Width (in)	Width (mm)
10	10	254
12	12	305
14	14	356
16	16	406
18	18	457
20	20	508
22	22	559
24	24	610