Thread: Baffle Box/muffler for DC enclosures

A couple of additional thoughts occur to me... If you don't have enough room on the inside of your already built DC cabinet nothing would stop you extending the baffle on the outside of the cabinet, for testing or permanent attachment.

Second thought / realisation... By having the cabinet around the whole DC, this is going to do the same job as putting a muffler between the blower outlet and the filter bags as a non enclosed setup. Except it would have the added benefit of supressing the noise at a much lower pressure.

Originally Posted by HeadScratcher

Bob what are your thoughts on the ideal shape of the baffles? Assuming for a moment you had the space to make whatever shaped baffle you wanted.
You mention making the area of the baffle ideally 4 times the intake area, but that volume could be made up of many different shapes, any best guesses on what that shape may be i.e. Triangle, square, rectangle etc.
I'm thinking possibly a rectangle to keep the air as close to two walls at all times. Thought, theories, experience with different shapes?

The air is elastic and at these low pressures when it is pushed one way it instantly pushes back inside the chamber which will make the air pressure the same everywhere in the chamber.
All this means the air cannot be forced closer to the baffles anyway.

The simplest way to reduce the noise is to increase the likelihood of sound colliding with the walls. This can be done by making narrower passages and more 90 degree, or even smaller angle, bends but a DC is tricky because the primary requirement is flow and doing this will hit the flow very hard. If resistance is an issue the the straight through muffler might be more suitable. (e.g. a 2HP machine).

A couple of additional thoughts occur to me... If you don't have enough room on the inside of your already built DC cabinet nothing would stop you extending the baffle on the outside of the cabinet, for testing or permanent attachment.

Yep

Second thought / realisation... By having the cabinet around the whole DC, this is going to do the same job as putting a muffler between the blower outlet and the filter bags as a non enclosed setup. Except it would have the added benefit of supressing the noise at a much lower pressure.

The enclosure does indeed act as a sound trap (that is after all the whole idea) but there is no difference between the pressure inside the enclosure and a baffle box - they will all be at the same pressure.

"Sound trap" is the operative term. This highlights the necessity for a good sound absorber inside the enclosure otherwise the sound will eventually escape out of the air exit. If 6"acoustic foam was used inside the enclosure you may not even need a baffle cox.

On my DC for space reasons I made the baffle box under the motor/impeller. If I had more space I would have made it on the opposite side so the sound would have been muffled a bit by the filters/bags etc.

Originally Posted by BobL

On my DC for space reasons I made the baffle box under the motor/impeller. If I had more space I would have made it on the opposite side so the sound would have been muffled a bit by the filters/bags etc.

That what I come up with this morning... Since the air has to exit via both filter bags I drew up a split baffle system and placed one under each collection bag. Each baffle is equal to twice area of the inlet.

Originally Posted by HeadScratcher

That what I come up with this morning... Since the air has to exit via both filter bags I drew up a split baffle system and placed one under each collection bag. Each baffle is equal to twice area of the inlet.

I still reckon you will regret those two internal walls that connect the impeller/motor direct to the external wall.

Your setup also has no air passing over the motor - this is essential or it will overheat.

It really is better to leave the whole internal thing open, rib the external walls for rigidity, and support the whole DC on the floor of the enclosure.

The impellor / motor has a gap at the front and back so it doesn't directly mount on an external wall, but understand your concern.

I have been thinking about venting the motor like this... If I kept the pipe work tight to the motor, cool air would be drawn in from outside, through the fan on top of the motor, what I don't know is if sound would escape back out that hole, and would need to let the hot air back out.

So that whole section is still under review.

Originally Posted by HeadScratcher

The impellor / motor has a gap at the front and back so it doesn't directly mount on an external wall, but understand your concern.

I have been thinking about venting the motor like this... If I kept the pipe work tight to the motor, cool air would be drawn in from outside, through the fan on top of the motor, what I don't know is if sound would escape back out that hole, and would need to let the hot air back out. .

Seems like more complication than is necessary. It's just a lot easier to let the air from the DC bags do the motor cooling. Unless you have a very old motor the small amout of dust in the air won't hurt the motor as they are totally enclosed these days anyway.

Originally Posted by BobL

Seems like more complication than is necessary. It's just a lot easier to let the air from the DC bags do the motor cooling. Unless you have a very old motor the small amout of dust in the air won't hurt the motor as they are totally enclosed these days anyway.

Yep think I might ditch that whole surround... I could always stick some foam to the outside to help dampen vibrations / noise.