Doors are the biggest source of sound leaks into a room. They create a large hole into a room and are likely only half as effective at blocking out sound as the walls surrounding them.
How to soundproof a door? It would be best to block any gaps letting air and sound through the door and surrounding frame. Install a pre-assembled soundproof door, or you can add mass to the existing door or the door area. And you can also utilize methods that create air pockets between the source of the noise and the room in which the door leads.
When planning on soundproofing a door, the first thing to do is identify if you’re looking at Interior or Exterior door treatment and dealing with a hollow core or solid core door.
Your door comprises four parts: two frames, a threshold, and the door itself. The rough frame is part of the wall, and the finish frame is made up of a top and two side jambs. The side jambs have latches and hinges on opposing sides to hold the door in place. And the threshold is the bottom part of the frame.
Exterior doors are usually only thermally insulated, which helps keep in warmth but doesn’t do much for soundproofing. They are usually housed in sealed frames with some form of threshold on the floor. On the other hand, interior doors are generally heavier, but not much attention is placed on sealing them.
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Install a solid core door
If you have a hollow-core door, then installing a solid core door would seemingly be the simplest, most immediate solution to your problem. You have a few options to do this.
It would help if you always looked for assembled, pre-hung doors. Pre-hung doors replace the finished frame (jambs) and the door itself. Also, choose a smooth slab rather than a recessed panel. And try to use interior doors with no threshold.
Option 1
Your first option should be a pre-hung solid core 1 ¾” slab interior door. This should give you a 35 STC rating which reduces loud speech to audible but not understandable.
As I mentioned earlier, interior doors don’t often come with airtight sealing or an automatic door button. So you’re going to have to do these yourself. The details on how to do this are mentioned further down below.
Option 2
If you are dealing with an exterior door and rather not replace the jamb or finish frame, then you can mount a solid core interior door slab into it. You benefit from the mass of the interior door and the airtight treatment of an exterior finish frame.
Option 3
An exterior door should be your last option. If you do go this route, then choose the heaviest one you can find. It may not be as effective as a solid core, but it will offer you better acoustic sealing than a hollow-core door.
The door will still be vulnerable if it’s unable to form a seal around the edges and at the bottom, so you will still be required to sound treat these areas. See sound treating door edges and installing a door sweep or automatic door button.
Install a soundproof door
A soundproof door is usually a four-layered acoustic-treated door that produces a 40 to 60 STC rating. At 41 STC, loud speech is barely audible, and 50 STC loud musical instruments are barely heard.
This is one of the most effective methods, which replaces the door and frame entirely.
Some will include an automatic door sweep, and most will include jamb seals that create an airlock system.
You may require some assembly of the door itself. Metal doors will need to be welded between the rough and finish frame and door. Installation of wooden pre-hung doors can be done with only a few basic tools (drill, screwdrivers, etc.).
Door sound treatment
You must do the next few steps to seal all air and sound gaps. If the door and frame are not adequately sealed off, the sound will leak through spaces and compromise the door.
Door sweep
A door sweep is used to block out air and sound coming in through the bottom of the door. This can reduce up to 70% of the air and sound traveling in. Once the sides and top of the door are treated, you will need to ensure an air-tight seal at the bottom of the door.
You will need to install this at the bottom of the door to block air traveling through the gap. The ones made out of silicon are flexible, and aside from blocking out air and sound, they can also help insulate a room.
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Automatic door buttons
Alternatively, you can use an automatic door seal for a door sweep.
An automatic door button works by pushing down a neoprene or rubber gasket onto the floor when the door is fully closed. A plunger or “button” on the edge where the hinges are placed is pushed in by the doorstop when the door closes. The button then pushes down the gasket in the aluminum frame and seals the gap at the bottom of the door.
It can be used by itself for any gap up to 3/4,” but for more than that, a saddle is required. Also, it’s not ideal when used with a carpeted threshold which will require a door saddle first.
Installation requires accurate measurement to ensure adequate clearance of the device within the jambs.
Sound sealing or weatherproofing for an air-tight seal
Airgaps need to be treated to ensure complete coverage and manage sound seeping in through the frame. It would be best if you did this on both sides and at the top of the frame. Weatherstripping requires little effort but, done properly; it’s an effective sound management method.
Most products use a peel-and-stick function. Surface preparation is required as the glue needs a clean area to ensure adhesion. An alcohol wash is not always required but is recommended. Installation should be done on the inner part of the frame.
You can use two methods for this:
Acoustic gasket
This is a foam rubber composite material that is a hollow “D” shape. When compressed, the gasket seals off and prevents airflow. If the gap is wide enough, you may end up with an air pocket which is just as effective as a soundproofing method.
Peel off the protective strip to expose the sticky side of the tape and then stick the gasket to the frame on all the edges as required.
Closed-cell foam
Acoustic-treated foam is the most commonly used material for this. It is compressed between the inner door frame and the door itself, preventing sound from traveling through.
Again peel-and-stick methods are commonly utilized for the application, which makes it easy to install.
Seal cracks and gaps around the frame
Air and sound may also leak through gaps around the frame, so sealing off this area is another “Must-do” step in the sound management process.
Caulking in a layer of Green-glue around the frame will effectively address this issue. A large caulking gun is needed, and applying to bead around the entire frame is recommended.
Once you have established an air-tight seal around the frame and there are no gaps around the frame itself, you can look at other areas to address.
Other methods to consider
Mass Loaded Vinyl (MLV) applications
Mass is a critical component in sound control and works by simply stopping sound from vibrating through its structure. Mass Loaded Vinyl (MLV) is an effective material to use in lining soundproofing curtains or blankets.
At even just ½LB per sq ft, MLV can produce a 25 STC rating, which is 1/16” thickness. You can get up to 35 STC by using 2lb per sq ft and 1/4” thickness; however, this is slightly more difficult to work with.
Installation would require you to cover the whole door and leave an overlapping edge and flush clearance at the bottom.
Soundproof blanket
You can use a soundproof blanket to add mass to an area and improve its sound-blocking abilities.
You can use many different blankets as long as you get as close to 100% coverage over the whole area. This may require cutting and fixing the blanket from the top and edges. You can use a staple gun or an adhesive to affix the blankets in place.
You can also use a grommet method. It would be best if you aimed at having the blanket overlap. It will be more effective this way, but you will still need to ensure an air-tight seal.
The grommets at the top will hold it in place. Adhesive strips along the edge and middle will give it a good finish.
Soundproofing curtains
These curtains can boast up to 20 STC ratings, about as much as a hollow-core door can produce by itself. However, this is only in the presence of an MLV or similar lining. Most curtains advertised as “Soundproof” curtains are merely light blocking, but they have limited effectiveness in blocking sound. Done right with the proper soundproof curtains will result in a noticeable difference in the amount of sound coming into an area. Even at a 10 STC rating, it will sound like half the noise as before.
Using soundproof curtains specifically designed to block out sound vibrations can be a useful option when you have mild sound issues. They can also use it in combination with your other efforts employed to enhance effectiveness.
You will need to install a curtain rail and aim for a 4″ overlapping width and height. You’ll also want to have the curtain hanging as flush to the wall as possible. This will avoid sound leaking out from behind the curtain.
Acoustic foam panels
The best acoustic foam panels are effective at basically stopping echo resonating from hard, flat surfaces. This does lend to managing some of the sound coming through into an area.
Installation requires the use of adhesion and covering the entire area with the foam panels. The typical result is a 20%-30% reduction which is only slightly noticeable.
You should use this method in conjunction with other methods to improve effectiveness, but as a stand-alone soundproofing method, this may be a bit disappointing.
Fill the hollow door
To fill a hollow door is another option. This can be achieved by spraying foam into the hollow areas of the door. The foam expands and adds density to the door. It’s as close as you can get to an actual solid core door without having to spend on one.
The challenge, of course, is accessing these areas and usually results in damage done to the door face, especially if the frame within the door has many vertical and horizontal beams.
You’ll also most likely need to remove the door to treat it with the foam and boreholes into the door face to access the spaces requiring treatment.
Other than that though, the application of the foam is a simple point-and-spray method.
Acoustic threshold
You may also consider building up a mini lobby area leading into the main house or room. This will require an appropriate amount of space, but if you have space, you could build a room as small as a 6X6. This can then be designed to make access into the area more convenient or private according to your desired door placement. The air-cavity created by this lobby would be incredibly effective against noise traveling in through a door.
Communicating door system
Another very effective method that doesn’t require as much space as a mini-lobby is a communicating door system. These are two doors in front of each other. One door opens inwards and the other outwards. The air gap between the two doors effectively deals with any noise traveling through. This method is often used for an at-home office or study.
Of course, both doors should be sound-treated around the edges and have a door sweep attached. This will essentially double the effectiveness of sound control.
Ideally, this method requires a thick wall that will house the door frames or castings. Also, special care will need to be taken to ensure clearance for the door handles. Furniture placement into the rooms may also need to be arranged to allow clearance for the doors.
Soundproof paint
Acoustic-Coat is heavy-bodied, water-based, flat latex paint formulated with ceramic microspheres and sound-absorbing fillers. The combination of high loading of ThermaCels with their vacuum centers reduces sound transmission; the soft pigment fillers absorb sound and prevent it from bouncing off the surface.
It is for use on interior surfaces such as primed drywall, ceilings, walls, plaster, metal, and wood. This product is an inexpensive, easy-to-apply surface coating with sound-absorbing properties, as compared to conventional paints.
Not only does it reduce the transmission of sound, but due to the heavy concentration of ThermaCels, it also provides a highly reflective heat barrier to the painted surface. This reduces heat intrusion into the adjoining rooms.
Conclusion
Soundproofing is a management process that consists of different methods to achieve a quieter environment. The methods to soundproof a door include mass loading, blocking any gaps, replacing your door. Using a combination of the methods mentioned above, you may be able to reduce annoying sounds coming through your door.
Good luck and happy soundproofing!