Flooring sound transmittal is an upstairs, downstairs, and everywhere problem. Footfall, music, TV, play, and other noises carry down to the floor below. Likewise, sound from below migrates through ceilings to the floor above. Even within rooms, various elements such as the flooring, walls, and furniture either deaden sound or act as amplifiers that encourage the noise to bounce around.
There are a few floor sound barriers that will mitigate the problem. While none of them make the problem go away entirely, these solutions, ranging from between-floor insulation to foam underlayments, can go a long way toward toning down the noise.
Insulation Between Floors
To truly block sound, you need to separate surfaces. Any kind of continuous material acts as a type of acoustic bridge that effortlessly moves vibrations from one room to the next. Structurally separating surfaces is an extremely costly solution and is usually reserved for spaces like home recording studios. Short of that, placing a sound barrier in the open joist spaces between the floors is an effective way homeowners to slow the transmission of noise.
This is done is by removing the ceiling drywall and inserting anything from R-13 to R-20 fiberglass insulation in the joist space. Invariably, you need to work around obstacles, like electrical wires and recessed lights that extend into the ceiling. New ceiling drywall is installed, and for added sound absorption, the drywall can be hung on resilient metal channels that let the drywall move slightly to deaden vibrations. A second layer of drywall makes this kind of barrier even more effective because it adds mass to the ceiling.
Flooring underlayment is installed primarily to provide a smooth, even, and predictable surface for a new flooring installation. Underlayment can refer to a soft layer, such as foam or cork, placed on top of the subfloor before installation of the flooring. This type of underlayment is typically installed under carpet or laminate flooring. Alternatively, underlayment can be a thin, hard layer of cement board or plywood. This underlayment may be used under laminate flooring, ceramic or porcelain tile, solid hardwood, or engineered wood flooring. It is even possible to use both types of underlayment in conjunction with each other.
Soft flooring underlayments typically come in long rolls and are made of foam or cork. Any foam underlayment, regardless of its physical properties, usually will advertise that it is effective against blocking sound. While these claims may have some validity, it is important to distinguish between this type of underlayment and others that claim to be acoustic underlayments. Acoustic underlayments are very dense materials designed to deaden sound vibrations. One quick way to determine density is to look at a material's weight in relation to its size.
Regular Polyethylene Foam
Foam underlayment is the least expensive but also one of the least effective products. This type of closed-cell foam is easily obtainable at all home centers and comes under many different brand names. SimpleSolutions Soundbloc is one brand offering. At 2 mm thick, this is the thinnest foam underlayment you can purchase.
Beyond the straightforward foam underlayment marketed for laminate flooring is another, more expensive type that is often called acoustic foam. This is a foam underlayment that is marketed as being effective at keeping floors quiet. WhisperStop is one brand of acoustic foam underlayment and is 3 mm thick, or about half the thickness of many cork underlayments. The Silencer is another acoustic foam and is fairly dense at 20 pounds of sound-absorbing material per cubic foot.
Recycled felt underlayment is both eco-friendly and effective for noise reduction. About twice as expensive as polyethylene foam, felt underlayment is a wise choice if sound absorption is your main objective and if your budget can handle the added cost. Recycled felt underlayment is about four times heavier than foam and thus denser. This is your best bet with engineered wood and laminate flooring.
Plywood underlayment is often used under thin, flexible flooring materials like vinyl or linoleum tiles. Plywood is only a modestly effective sound blocker. Red rosin paper or tar paper (roofing felt), which have no sound-blocking advantages, are sometimes laid on top of the plywood to minimize squeaks, but this benefit is subject to debate in the flooring industry.
You can do better than plywood underlayment by installing specialized acoustical underlayment on the subfloor. Soundeater is one such product that is made from 100 percent recycled wood. At 1 1/16-inch thick, Soundeater is thicker than most ordinary plywood products, so make sure that this does not cause a problem with floor levels in adjacent rooms.
Acoustic underlayment systems differ from the straight plywood option because the systems elevate the flooring on sleeper boards. This elevation creates a dead air zone that significantly reduces the transmission of vibrations from one floor to the next.