I built my home with special sound-proofing for my home office. I put in sound board, insulation, two solid-core doors, acoustic foam, and thick carpet. But there was one problem.
All of it did practically nothing because I had a completely open vent above the door which let sound pass through easily.
There are basically two ways to approach this soundproofing problem: (1) block the vent entirely, or (2) create a sound maze.
Blocking the Vent Method
The most soundproof approach is to remove the vent and drywall over the hole, but that’s a lot of work and cost that could have a much simpler solution. Instead, you could simply take the vents off, spray the area with gap filler (link to Amazon) so it entirely seals the area, and then put the vents on so that it looks normal again.
There is a huge problem with this approach. It’s that the room will likely get very hot during the summer. The air flow vent is there for a reason. It allows air to pass through the top of the doorway so that the room can be efficiently heated and cooled.
I made this mistake in my home office. I drywalled off the vent and the room has been difficult to keep cool. It hasn’t been horrible, but a little uncomfortable. In my next home office (we’re planning to move soon), I plan on testing out method #2.
Sound Maze Method
This method takes a little more work, but it will result in a room that is quiet but easily heated and cooled.
The way this works is that you make a miniature maze inside the vent space using pieces of thin wood with acoustic foam taped to the wood scraps. This way, the sound has to zig-zag around several times before entering the room, which will significantly deaden most sounds.
Materials needed to create an air duct sound maze
- Small amount of acoustic cotton or foam. I’d use this foam available on Amazon.
- A small amount of 1/4″ plywood
- A saw
- Small screws
The down side to this method is that it isn’t as effective at blocking noise as simply drywalling off the duct or blocking the duct. However, it should dramatically cut the amount of sound compared to leaving the vent open.
I have not yet personally tried this method, but I’ve heard good things from those who have tested it.