Soundproofing

If you desire a room with enhanced soundproofing qualities, a good time to provide for it is when installing insulation.

Soundproofing is rated by a system called Sound transmission class (STC); the higher the STC rating, the better the soundproofing qualities of the wall. In addition, since air transmits sound, any air spaces left in the wall (such as around outlets, plumbing, vents, and wiring) will adversely affect the STC.

An STC rating of 20 to 25 allows normal speech to be heard through the wall; a wall with an STC rating of 42 reduces normal speech to a murmur. A 2X4 frame wall with fiberglass insulation and drywall on both sides will provide a moderate STC of 39. The same wall with a double layer of drywall on the soundproofed side will increase the STC to 44.

The top layer of drywall is installed using sound channels; creating air space between the layers of drywall. The same wall can be slightly improved by using acoustical tile instead of the second layer of drywall, the STC rating can be increased to 46. This can further be enhanced by using a little different design in the stud wall itself.

Enhancing STC Rating

To enhance STC rating, install 2X4 studs vertically on a 2X6 top and bottom plate when constructing room walls. Stagger the 2X4 studs so that they alternate being flush with either side of the plates. Weave fiberglass insulation into the middle space between each, with batts running horizontally.

Once both sides of the wall are finished off with ½-inch drywall, the resulting STC is an impressive 48. Note: at an STC rating of 50, a loud voice or shout cannot be heard on the other side of the wall.

Other Sound Proofing Material Options

One inexpensive alternative to regular insulation is foam sound proofing material. The foam comes in ½-inch to 2-inch thicknesses, enabling it to fit into any space. STC ratings using the foam run between 40 and 50.

Vinyl sound proofing materials yield even more impressive results, with ratings between 42 and 55. And Metal wall channels have STC ratings of 38 to 50. Of course, home location, the nature of the noise, and homeowner budget are all determining factors on which soundproofing techniques will work best.

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