Baffle Box

[hashisheen]

Has anyone tried building a custom baffle box for an inline fan ?
Im in the process of doing this myself but have a couple questions regarding its design.

Should the intake and outtake on the box be at 90 degrees to each other?, is the trade off ( throughput for dampening ) worth it?

Is it a good idea to fill the box with some kind of medium as well as line it?

Atm im building 1" mdf boxes with a half meter cubed internal space, sealing the whole lot with silicon sealant, then plannning on lining with impact foam or the like if i can find some, and screwing it tight.

Any tips greatly appreciated !

 

[NDS]

Well, they dont have to be on 90deg angles to each other, but for every 90 deg angle there will be a level of dampering.

Remember to keep the required open area the same all the way through the baffle.
It may help to think of your baffle box like a car muffler.

Notice how there is no direct line out for the air? also means no direct line out for the sound. Sound moves in waves and reflects off most surfaces very well, alot like water. In fact, you can make a model of your baffle box out of a small rubbermaid container, and a few pieces of plastic. Put some water in the container and drop a stone in one end, watch the waves go from 1 end to the other and back. Now add some plastic pieces in there and see how it redirects the waves. Basically, you want to add panels until there is no wave transferance to the other end of the container.

As for sound absorbtion inside the baffle box, Acoustical Ceiling Tiles. they are cheap and highly effective. Stay away from flat surfaces, they reflect noise better then an imperfect one.