Soundproofing in a home usually involves one of two approaches: keeping sound out of room or keeping sound in a room. For a home theater space or music room, the objective is to keep the sound in so it doesn't travel to other areas of the house. Bedrooms usually belong in the other category; you want to keep out noise from other rooms and the outdoors to make the bedroom as quiet as possible. However, you may also want to minimize noise inside a bedroom so that an awake person can move about more freely without disturbing someone sleeping. There are several options for addressing noise both inside and out.
A Brief Introduction to Soundproofing
There are two basic concepts for understanding sound (in this case, noise) and soundproofing. First, sound travels by sending vibrations through the air. It can also send vibrations through materials (like wood and drywall), which in turn vibrates the air on its way to your ears. Therefore, the primary goal of soundproofing is to block or absorb sound vibration.
The second concept involves the two types of noise. Impact noise comes from things such as footsteps or bowling balls overhead or from crazy neighbors bouncing off the walls. Airborne noise comes from honking car horns or drunken nightclubbers outside or from a TV in the next room.
If sounds are coming from other rooms in your own house, you can employ soundproofing measures inside and/or outside the bedroom. If sounds are coming from outdoors or from neighboring units, you're limited to soundproofing strategies for inside the bedroom.
Sealing Air Leaks in Walls and Ceilings
When soundproofing walls and ceilings between rooms, the first thing to look for is air channels. Likely culprits include electrical outlet and switch boxes, gaps behind baseboards, and HVAC vents. Air is the best vehicle for sound, and any gaps or openings that let air through will also usher sound directly into the room. Windows and doors are other common sources of air leaks, and those are discussed below.
You can seal air leaks at electrical boxes with special soundproofing outlet/switch covers, soundproofing putty or foam gaskets. For baseboard gaps, remove the baseboard and apply acoustical sealant between the drywall (or plaster) and the floor, then reinstall the baseboard.
Air vents are a bit more complicated. Since they're essential to heating/cooling your bedroom or circulating fresh air, you can't cover up vents permanently. But if you really need some peace and quiet for a while, you can close a vent and cover it temporarily with a magnetic vent cover (to seal out air) as well as a piece of acoustical foam or a soundproofing material like mass loaded vinyl (MLV), a thin but very dense vinyl material that comes in rolls.
Soundproofing Bedroom Walls and Ceilings
The next level of stopping noise through walls and ceilings is to reduce the transmission of sound through the wall or ceiling assembly. Possible solutions range from rebuilding the wall to applying soundproofing materials on the bedroom-side surfaces:
- Add sound-absorbing insulation, such as rock wool batts, between framing members if the wall or ceiling framing will be exposed, such as during remodeling activities.
- Layer an exposed wall with an MLV sound barrier and one or more layers of soundproofing drywall.
- Add an MLV sound barrier and a layer of soundproofing drywall over the existing wall or ceiling surface.
- Use noise-proofing compound (such as Green Glue) when installing new drywall over old. This is a special caulk-like material that reduces vibration transfer between the drywall layers.
- Install resilient channels over the existing surface, then add a layer of soundproofing drywall. Resilient channels are metal strips that move slightly to help the drywall absorb vibration.
Soundproofing Bedroom Floors
The best and easiest way to make a bedroom floor quieter is to install wall-to-wall carpet with a good, dense pad. Carpet not only silences footsteps inside the room, it also absorbs airborne sound and prevents echoing that contributes to ambient noise. If you're ready to replace your bedroom flooring, you can take the soundproofing a step further by refastening any loose areas of the subfloor (to stop squeaks) and taping the subfloor joints with metal tape (to stop air leakage). Then, you can add a layer of MLV sound barrier (and tape the seams) before laying down the carpet pad. MLV also is available with an optional acoustical foam layer for additional floor soundproofing.
Soundproofing Bedroom Doors and Windows
Doors and windows can be the biggest contributors to noise transmission in a bedroom because they're made with relatively thin materials, and they're usually riddled with air gaps. Therefore, the solution is two-pronged: add density and stop air leaks.
To add density to a door—especially a thin, hollow door—you can install a layer of MLV or acoustical sound board to the room-side of the door, or you replace the door with a solid, slab-style door, which is thicker overall than panel-style doors. To stop air leakage, remove the door trim and seal around the rough door framing with acoustical sealant, and add weatherstripping to the sides and top of the door opening, just as you would to seal out cold air. Most important, add a threshold and/or door sweep to seal any gap at the bottom of the door. Even a small gap here can let in a tremendous amount of sound.
Air-seal leaky windows just as you do with doors, using acoustical sealant and weatherstripping. As for the glass itself, if you have quality double- or triple-pane thermal windows, they're probably pretty soundproof as is, but if you have old single-pane windows or older thermal window that don't seal very well, you have a few options:
- Add clear plastic window inserts, which provide a secondary air barrier and create a dead air space between the window and the insert, much like old-fashioned storm windows.
- Install heavy soundproofing drapes. It's best if these extend from floor to ceiling and at least 3 inches beyond the sides of the window. Another, more streamlined, option is soundproofing blinds.
- Build your own window plugs—removable panels made with plywood and a thick layer of acoustical foam insulation (and perhaps a layer of MLV). A plug fits snugly into the window opening to block air, sound and light. You simply plug them into place when it's time to sleep, and store them under the bed or in a closet when they're not in use.
Reducing Bedroom Noise With Decor
Despite claims to the contrary, décor items—like wall hangings and soft furnishings—will do very little to keep sound from coming into a bedroom. What they can do effectively is reduce noise generated inside the room. They do this by absorbing sound vibrations and suppressing echo. Of course, soft and deeply textured materials do this much better than hard, smooth materials. If you keep this rule in mind, any décor features you add will help minimize noise, from upholstered furniture and tapestries to area rugs (if you don't have carpet) and throw pillows.