Isolation Baffle - Sound Proofing

To make my studio more comfortable, I needed to let air in without letting sound out. To do this, I built two baffle boxes: one near the floor to let cool air in and one in the ceiling to let warm air out. The baffles inside the box force air around sharp turns to decrease the volume of sound waves. By avoiding parallel surfaces inside the box, I limited the propagation of standing waves that might actually increase the volume of certain frequencies. I used 2x8 boards to build the baffles and the frame.

First I cut the baffles. Each baffle is two inches shorter than the width of the frame to accomodate two half-inch thick pieces of cellutex soundboard and one inch for air to flow. I cut five baffles with 90 degree edges, and four with 75 degree edges to prevent standing waves between the baffles (the cellutex covering in the pictures below was added later.)

I traced a hole for the air input on a long piece of 2x8. Then I traced where each baffle would go. I drew a line 1/2 inch around the edges of the baffles and the edge of the board to make sure there would be enough space for air to travel after the cellutex was added. On the other end, I left space for the air output hole on the other side.

For the two air holes in the board, I used the plumbing pieces pictured below. From left to right they are a floor mount, a screw on cleanout cap and a threaded cleanout.

I measured the length of the board that I had drawn the baffle outline on and cut three more boards the same length. I put two boards on top of each other and the other two boards on either side. Then I cut two small pieces for each end. I placed each baffle piece in the trough, drew a line across them at the height of the side boards, and cut the baffles to that size.

I screwed the end pieces onto the side pieces. I rested the bottom and top boards in place so the frame would hold its shape and everything would fit snugly. Then I removed the top, placed each baffle where I had traced them earlier, and screwed them to the side boards. I removed the bottom board and used it to trace a piece of cellutex the same size as the board. I placed the cellutex back under the baffles with the board beneath it for support. Then I traced the outline of the baffles on the cellutex.

Next I used a drywall saw to cut out the shape of the baffles on the cellutex. I cut the air hole circle out of the bottom board and used the hole in the board to trace the hole on the cellutex. I turned the baffle box over, placed the cellutex piece over the baffles and trimmed it to make it fit. Then I traced and cut an identical piece for the other side bearing in mind that the air hole has to be on the opposite end.

I put the board on top of the cellutex and turned the baffle box over again. I screwed the cellutex to the board with 1 inch dry wall screws. I fit the clean-out pieces together, put it through the air hole and screwed it down with 1 & 1/2 inch dry wall screws.

Next I cut the cellutex to go on the baffles. I measured their length, and their height minus a half-inch to allow for the cellutex on the top board. I unscrewed the baffles one at a time and screwed on the cellutex pieces.

Before I screwed the baffles back in, I applied wood glue to the bottom of them and a liberal bead of a silicone caulk that's normally used for windows and doors. Once all the baffles were back in place and I had wiped all the excess caulk and glue from the edges, I cut pieces of cellutex to go around the sides of the baffle box and screwed them into place.

I put all the pieces together to make sure they fit...

...then I applied glue and caulk before screwing them back together.

The ends went on last.

The finished product: