How to Soundproof a Room With Caulking

Man using caulking gun, close-up
Vstock/UpperCut Images/Getty Images

Perhaps it’s the dog or the new baby in the other room. Or maybe your partner likes to watch videos in the other room while you’re trying to sleep. Whatever it is, the sound is bothering you and you need to soundproof your room.

While soundproofing involves a battery of several tactics—some of them quite elaborate—there is one surprisingly easy and inexpensive way to cut down on the sound. For very little money and effort, you can reduce outside sound by as much as 15-percent. It doesn't seem like it should work, but it does: Applying caulking to cracks.

Reducing Airflow Helps Reduce Sound

Professional soundproofing is highly expensive. It involves adding insulating materials and extra drywall—or replacing existing wall materials with new and more expensive materials. It often involves other people and special tools: contractors and consultants and decibel meters. All of that means more expense, more time, more effort.

But one way to cut down on the transmission of sound is to reduce airflow. Physics tells us that sound is borne by air since sound is vibration traveling through the air. Wind promotes the transmission of sound even more.

If this seems improbable, it's easy to conduct a simple test of this notion. Crack open a window by 1/2-inch or even as narrow as 1/4-inch. Take note of the sound level in the room. Shut the window and notice how the sound changes.

Locating Cracks That Allow Sound

Think of the room that you want quieter as having air flowing into it from the outside. How is the air escaping into your room? The gaps between outlet boxes and drywall are one area. Another area: gaps under doors. If the sound is coming from outside, airflow coming through or around windows is another place to look.

Even these very narrow seeps of air carry sound. Remember that sound is caused by vibrations traveling through the air. The type of thinking that is used to detect cold air coming into your house is the same type of thinking needed to detect sound carried by airflow.

  • Through or around receptacle boxes
  • Through ceiling receptacle lights
  • Cracks above windows or doors
  • Poorly fitting windows
  • Misaligned doors
  • Gaps in wall insulation
  • Thin wall patches (holes in walls patched not with drywall but with fiberglass patch material)
  • Cracks in floorboards

Using a Thermal Camera to Locate Sound

Since cracks that permit cold air are the same cracks that permit sound, use a tool that contractors employ to find out where the cold air is coming from: a thermal camera.

Low-cost thermal cameras are available that plug into your smartphone. Through the camera's app, all of the cold air entering your home will be identified in darker colors like blue or green.

You can only use a thermal camera when there is a sharp contrast between the inside and outside temperatures. So, fall or winter are the best months to use a thermal camera to locate cracks that permit both cold air and sound.

How to Block Sound Carried by Air Seepage

Caulk, weatherstripping, and insulation are fitted into every available crack that neighbors the exterior or a particularly noisy adjacent room.

Depending on the surface, you may want to use painter's caulk since it can be painted over to match the surrounding surface. If the cracks are exterior-facing, use exterior-grade silicone caulking.

  1. Caulk around outlet boxes for a tight seal.
  2. Install weatherstripping along the leading edge of windows.
  3. Place weatherstripping in large cracks around doors and windows.
  4. Fill small holes or cracks in drywall with caulking (or better, drywall compound, and then painting over it).
  5. Fill in cracks in floorboards.
  6. Put up storm windows.
  7. Put up a storm door.
  8. Fill in large holes with material that matches the surrounding surface. Large holes in drywall should be patched with drywall, taped, mudded, sanded, and painted.
  9. Repair windows so that they close tightly. If you cannot repair the window, have it replaced.

How Much Sound Can You Block?

Sound Transmission Class (or STC) is used by sound consultants to measure sound levels. STC is not the same thing as decibels. STC is a general range, not a precise measurement.

In the 30-35 STC range, the person in the next room who is talking loudly can be heard in the intended quiet room. By merely caulking, you can reduce that STC rating by about 15-percent. So, the loud voice is mitigated, but not stopped.