Sound can transmit through doors much easier than walls because a door is much less dense than a wall and there are large gaps around the perimeter (especially at the bottom). Double doors have even MORE gaps than a standard door, because there’s an opening at between the two doors - making them more likely to need soundproofing. Before we discuss some techniques for soundproofing your double doors, let’s go over the type of sound you are likely dealing with.

Airborne Noise

When it comes to soundproofing any type of door including double doors, airborne noise is the type of sound you are trying to block. As the name suggests, airborne noise is transferred through the air. In a residential setting, examples of airborne noise that could be heard through your double doors include loud music, kids playing in another room, or dogs barking. In a commercial setting, double doors may be used to separate noisy spaces such as a meeting room and the break room.

Impact Noise

Impact noise is not a concern for double doors or french doors. Impact noise is caused when an object hits a surface, causing the surface to move and vibrate. It is more common to soundproof for impact noise with floor/ceiling constructions, because impact noises enter the structure most commonly through the floor (ex: footsteps and operating machinery). Since impact noise isn’t going to be stopped by a door – these types of noises should be solved using other methods.

Soundproofing windowless double doors is simple and is essentially the same process as with a standard door with a couple of key differences.

Here are the two main things to look out for when soundproofing a double door.

The Double Door is Dense Enough to Block Sound

Any barrier needs to be solid and dense to efficiently block airborne noise. That is why we always recommend purchasing solid core doors when installing double doors. Hollow core doors are not dense enough to block much sound. So no matter what you do to seal up the gaps around the door, there will surely still be a good amount of airborne noise transmitting through the door itself. For soundproofing, you need a solid core door.

The average solid core door will have an STC rating of 30-35, while a hollow core door will have an STC rating of 20-25. The 10 STC rating difference may not seem like much, but it will effectively cut the perceived sound in half!

There is an Airtight Seal Around The Perimeter of the Double Door

You will also want to make sure that the perimeter around the door is sealed to prevent any noise from slipping through the gaps between the door and the door jambs or the door jambs and the wall. We close these gaps with an adjustable door seal kit for the door itself, and acoustical sealant for any gaps between the jamb and the wall.

Sound Lock Door Seal Kit

Our Sound Lock Door Seal Kits are a great way to seal the perimeter of doors. The seal kit even includes a drop-down seal at the bottom of the door that becomes flush with the floor when closed. You can get up to 20 STC points of improvement to your double doors if you use this product. The Sound Lock Door Seal Kit should only be used on a solid core door to ensure maximum sound blocking ability.

Our door seal kits are designed for single doors or double doors. For double doors, reach out to one of our soundproofing experts at Second Skin, and we will provide you with a specific quote. Since double doors also need to be sealed where the two doors meet, we include an astragal seal that allows our door seal kit to also seal that middle gap. We also offer alternatives door sealing kits, like our Sound Lock Gasket Seal Kit. This kit contains a bottom door seal and a roll of gasket seal tape!

Sound Lock Soundproof Door

Our Sound Lock Soundproof Door is a perfect all-in-one purchase that can be built as a double door. For the double doors, we do a knock down frame so it's easy to get the door to the job site. It's an attractive door that's easy to install - which makes it an excellent solution to soundproof a door. The unit has an STC rating of up to 56 and can even be customized to come with windows, made using our Tru Acoustics Soundproof Windows, allowing the door to maintain top-end performance well even with a viewing window.

Feel free to reach out to one of our soundproofing experts for a double door quote on the Sound Lock Soundproof Door. Also check out our guide on soundproof door costs.

French doors imply you have windows in the doors, and this is the most important part to address when soundproofing french doors. We recommend a soundproof window insert for French door soundproofing, on top of sealing the perimeter of the door with a door seal kit. French doors have a lower STC rating than a typical solid core door, but there are still a few ways to improve on them.

Step One: Install Soundproof Window Inserts

The Fantastic Frame Soundproof Window Insert is the best way to reduce airborne sound transmission through the window in your French doors. The window insert is installed using metal trim pieces that allow the insert to magnetically connect to the door and discretely soundproof the door’s windows. There's a wide range in cost to soundproof a window depending on the solution though, and we do have a handful of other methods we have used.

When adding window inserts to a French door, we need to check for fit . We have a few images below to help:

1. 1. There needs to be about 1" of space around the perimeter of the windowpanes for the insert install.
   2. The window insert needs to completely cover the all of the glass for this to be effective.
   3. If your door has knobs, GREAT! If not, the handles would need to stand out farther than the frame so they can still turn, which is about 1” off the door.
   4. For doors facing the exterior, window inserts should be installed on the interior side.

Step two: Seal the Door Well with a Door Seal Kit

Just as with standard double doors, a door seal kit is needed for sealing around the perimeter of french doors. Chances are your french doors will be exterior facing and sealed up with weather stripping. But if you are taking steps to soundproof interior french doors, it is imperative to seal around the perimeter or they will allow a lot of noise to pass through.

Step Three: If You Want Soundproof Curtains as well - USe Sound Blankets

If you’ve searched around the internet, it sounds like soundproof curtains are a popular solution, but they are actually not very effective. Most products advertised as soundproof curtains are not STC rated and not dense enough to actually block sound. Aside from having minimal impact, adding a curtain to your french door sort of defeats the purpose of having a window there. For a material to be able to block sound, it needs to be very dense with an airtight seal. Most curtains are nowhere near dense enough to be considered soundproofing materials.

If you are dead set on a soundproof curtain, your best hope is a product like the Quiet Quilt Soundproof Blanket. This product would not be ideal for an interior door because it isn’t very aesthetically pleasing, but it can be used for exterior french doors. The Quiet Quilt Indoor Soundproof Blankets are STC rated (STC 32) and are dense enough to block sound. rather than using these and/or a window insert, you may be better off froma performance standpoint of switching to a doube door assembly with solid core doors

Whether in the office or at home, now you know how to properly soundproof your double doors, and you can finally block out the noise of your loud colleague or your roommate's horrible music preferences.

Contact the soundproofing experts at Second Skin Audio with any questions on your soundproofing project.