How to Soundproof an Above-Door Air Vent


There it is. The enemy!
There it is. The enemy!

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.

You can see straight through both sides of the grates on the door. Without blocking the space off or making a sound maze in the middle, all of your other soundproofing efforts will be useless.
You can see straight through both sides of the grates on the door. Without blocking the space off or making a sound maze in the middle, all of your other soundproofing efforts will be useless.

Blocking the Vent Method

This is what it looked like after drywalling off the vent over the door.
This is what it looked like after drywalling off the vent over the door.

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.

This is a drawing of what the sound maze looks like. The bottom of the drawing is out in the hall, the box is the area between the metal grates on either side of the door. The gray bars are the pieces of wood covered with foam that you glue in there to make the sound maze.
This is a drawing of what the sound maze looks like. The bottom of the drawing is out in the hall, the box is the area between the metal grates on either side of the door. The gray bars are the pieces of wood covered with foam that you glue in there to make the sound maze.

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

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.

5 thoughts on “How to Soundproof an Above-Door Air Vent

  1. Hi Jm,
    Came across your blog which is interesting and helpful. I will use some tips from it. However, I wonder have you any other tips for me. My issue is not blocking outside noise or acoustics. I work as a psychotherapist and need to ensure that what is said in the room does not escape the from the room (as much as possible). In particular, through a door. Is the answer the same as excluding external noise or not?
    Thanks & Regards,
    Paddy

    1. I know that this question was asked last year but this will hopefully reach you .
      Your issue is a little different . While this idea would help to diffuse some of the noise, it really doesn’t make it sound proof. You will probably need a combination of solutions to take care of this problem.
      Along with the idea from this article you will need to work on masking the sound that is coming from the room . A white noise machine should make the sound coming from the office much more difficult to hear and will make it hard to make out individual words. It works by making a low pitched static sound that sounds like background noise. When the level is right people won’t even recognize that they are hearing the white noise.

  2. I have a larger grill opening above the door and have the same situation where I need the any vocal communication to stay within the room. Will a combination of an interior baffle/maze along with sound absorbing panels hung across the exterior grill (approx. 3-6″ away from grill) be effective in containing the voices?

  3. I have a return directly infront of my HVAC fan abover the staircase to our 2nd floor. Everytime the machine turns on it sounds like sn airplane is landing. The vent is literally right in front of thd fan and no space to put additional ducts to dampen the sound. Any suggestion?

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