Sound insulation is used to reduce sound transmission between two areas of a building. When applied in the roof or ceiling, this insulation can keep noise from passing between levels of a building. It can be used to control noise from footsteps, TVs and radios, or everyday conversation. There are a number of different techniques that can be used to insulate a ceiling depending on your budget and existing ceiling configuration.
Insulating Existing Ceilings
The most effective way to insulate an existing ceiling is to add a second layer of ceiling material below the first. The interstitial air space between the two surfaces helps to trap noise and reflect sound waves. Start by installing hat channel framing along the surface of the existing drywall ceiling. Use sound isolation drywall clips (sometimes called resilient or sound clips) to suspend a new sheet of drywall along the hat channel. You can use regular drywall, or use a product designed for sound control like QuietRock or STC-rated drywall. Leave a 1/4-inch gap between the edges of the ceiling and the existing walls to help reduce vibration-related noise. Fill this gap with acoustic caulk to help conceal it without adding noise.
Another option for existing ceilings is to use a sound-control product like Green Glue. This product is similar to caulk, and is used to transfer sound energy into heat. It must be sandwiched between two sheets of solid material like drywall or plywood to work effectively. Spread Green Glue across the entire surface of the drywall according to the manufacturer's instructions, then screw a second sheet of drywall directly over top. While Green Glue is fairly expensive, this technique will save several inches of ceiling space compared to using a hat channel and sound clips.
For a simple low-cost option, cover an existing ceiling with foam or cork panels. These panels are designed to minimise sound transfer, and are often covered in attractive fabric to add aesthetic appeal to the ceiling.
Insulating a New Ceiling
There are several ways to add sound insulation to a new ceiling. If you want a drywall finish, use rigid or spray foam to fill the space between ceiling framing joists. Add at least one layer of sound-resistant drywall, or use two layers for added noise control. Maintain a 1/4-inch gap around the perimeter of the ceiling to reduce vibration noise from above.
Another option is to use an acoustic tile ceiling. This product consists of a steel grid that is suspended from the ceiling by metal wires. The grid is filled with acoustic gypsum tiles that help to absorb and muffle sound. Special "quiet" tiles are also available in areas where noise is a major concern. These grid ceilings are fairly inexpensive and easy to install.