I've got 40+ small blowers in the cleanroom that are used to cool a motor by pulling room air through the motor. They're spec'd by the mfr and I can't change them. At the air output end they scream at 2643hz (recorded on my mp3 player and run through TrueRTA), and since the sound was driving everyone nuts, we vented them out of the room.

The problem is this: With that much air leaving the room I'm having trouble maintaining temp, humidity, and pressure in the room.

I want to build a small acoustic trap to go on the output of the blowers to kill that frequency without adding back pressure or costing much and I thought that a small tuned enclosure might do the trick. I can't use fiberglass batting or anything that would particulate, which includes wood, but I could model it in wood.

The blowers put 50cfm each through a 1.25" opening.

Thoughts?

Thanks, John