Baffle Box/muffler for DC enclosures

Several members have asked me about baffle boxes and mufflers for DC enclosures so rather than respond every time I will start a thread about it.



The type of muffler/baffle box that should be used depends on a number of factors such as, how loud the noise is you want to attenuate, the level of sound reduction you want to achieve, and where the sound is coming from.



A simple tube or long rectangular box made of a hardish material (e.g. chip board or MDF) lined with a few inches of foam rubber may be sufficient to vent air out of the enclosure.



OTOH if you wish to reduce the noise level even further some sort of baffle box is one way of doing this.



Baffle boxes can be made in may ways and the one I will show is just one example. Unlike car mufflers and such like the cross section of the air path should not be constrained in any way.

Because Baffle boxes require the air to turn through multiple 90º turns this will add to the back pressure of the DC and reduce the flow at the source of the dust collection. To get around this the cross sectional are of the air path should be at least double (and preferably quadruple) the cross sectional area of the air intake to the DC.

• The baffle box consists of a large rectangular tube (made from something hard like MDF of other timber) that has a series of evenly spaced board (baffles) that protrude into the internal space


• The baffles and the entire internal structure of the box should be lined with a sound absorbing material (SAM) like soft dense foam rubber or similar material, thick carpet would be OK.


• The length of the baffles should be long enough to force a full 90º turn in the air path. Sorter baffles will still work but not as effectively.


• Remember to take the SAM thickness into account when designing the box because the x2 cross sectional area recommendation does not include the area occupied by the thickness of the SAM.


• The more baffles and thicker the SAM you have the better the sound reduction will be but of course the greater the restriction to flow. To get around this problem you can make the air path cross section greater but that will allow more sound to escape.


• Rather than the number of baffles used, another way to think about a baffle box is to count the number of 90º turns the air has to make.


• You can play around with numbers of 90º bends but there will come a point that, unless you are using a concrete bunker as an enclosure, there will be more sound escaping from other parts of the enclosure than there will be from the exit from the baffle box


• The baffle box below has 8 x 90º bends which should be more than enough. My baffle box has 6 x 90º simply because that is all I have the room for inside the enclosure.


• If you have limited room you can trade off either the thickness of SAM or even just put the SAM on one side of the baffle.


• My setup uses 2" thick dense foam rubber mattress material that I picked up from hard rubbish collection.


• The other important feature of a baffle box is theilocation of the exit. Locating the baffle box exit down near the ground will make it a but quieter than high up like I have shown as any escaping sound has a greater chance of being absorbed by objects near the ground instead of immediately projecting out around the neighborhood.

Attached Images

• Bafflebox.jpg (40.1 KB)