Sound is often a problem within homes. If you're lucky enough not to have exterior sound migrating to the inside of your home, you may have sound moving from room to room. Various methods can be used to reduce sound transmission in interior spaces in your home. But one method of soundproofing that is often overlooked is one of the simplest: installing a soundproof interior door.
Soundproof Interior Door Options
Sound transmission within a house often occurs because the wall system transmits vibrations from one room to the next. Interior doors are a major contributor to room-to-room sound since they are just one layer and often this layer isn't very solid. Replacing the door alone will greatly reduce sound transmission.
Solid Composite Interior Door
Wood composite is a slurry of wood fiber and polyurethane resins that can mimic the look of real wood and provide excellent insulation against sound. In most cases, installing a solid composite interior door will improve soundproofing when it replaces a standard hollow-core door.
Hollow-core doors are braced with cardboard honeycomb materials. The honeycomb structure is empty space. A solid composite interior door provides up to 70-percent more material than a hollow core door. An advantage of composite wood is that it will not warp, shrink, or crack.
Composite interior door surfaces may be flat or embossed. An embossed composite door will seamlessly replace a six-panel hollow-core door while giving a Sound Transmission Class (STC) rating of between 27 and 30. An STC class of 30 is one where a conversation of a normal volume can be heard and understood.
Solid Wood Barn Door
Because this barn-style door slides on a track mounted above the door frame, it can be thicker and thus more soundproof than a door mounted within the doorframe.
Sound is vibrations. Vibrations move from one room to the next through attached surfaces. So, breaking the bond between those surfaces greatly reduces sound transmission. Interior barn doors hang from tracks mounted about the door opening, so there is very little surface contact between the door and the wall.
Interior barn doors are well-suited to DIY installation. Because the door overlaps the door frame, there is no need to precisely fit the door within the door frame. Not only that but there is no need to mortise hinges.
Enhanced Hollow Core Door
Replacing standard hollow-core interior passage doors with solid doors is the best way to ensure a quieter house. But with costs starting at $300 to $400, solid core doors may not be economical for many homeowners, especially when several doors need to be replaced. One solution is to improve the hollow core door:
- Add a door sweep
- Weatherstrip the door
- Seal gaps and cracks around the door with painter's caulk
- Add a soundproofing blanket
Basics of Sound Transmission in a House
Sound Transmission Class (STC) ratings assign a measure of the acoustical performance of a door, wall, or other household material. Higher STC values indicate a better ability to resist the transmission of sound.
- STC 25: Normal speech can be clearly understood
- STC 30: Loud speech can be understood; normal speech is heard but not understood
- STC 35: Loud speech audible but not understandable
- STC 41: Loud speech sounds like just a murmur
- STC 45: Loud speech is barely audible
- STC 50: Loud musical instruments barely heard
STC Ratings For Doors and Walls
If interior walls are a weak enough barrier against sound within a home, then any wall penetration only promotes sound transmission. Doors are a weak link, with hollow-core doors being the weakest of all types of interior door.
STC Rating | House Element |
20 to 25 | Most interior hollow-core doors |
30 | Solid door, particleboard core |
33 | Standard interior wall with 1/2-inch drywall on both sides and 3-1/2 inches of airspace |
39 | Interior wall with 1/2-inch drywall on both sides and 3-1/2 inches of space filled with insulation |
45 | Double layer of 1/2-inch drywall on both sides (for a total of four layers of drywall), with 3-1/2 inches of space filled with insulation |
55 to 60 | Solid wood slab door |