| Today's homes are louder than ever and | | | | the other through mechanical paths (like studs or |
| everyone would like things quieter. The question is | | | | joists). Instead, the vibration has to pass through |
| what to do? Obviously no one wants to spend big | | | | the air cavity between the studs, where some of |
| bucks on soundproofing, only to spend time and | | | | it will be lost, and through the insulation/absorbing |
| money in vain and still hear plenty of noise. | | | | material, where (at higher frequencies) much of it |
| Sound isolation is science, not magic, and as such | | | | will be lost. |
| it is possible to outline a foundation of basic | | | | Principle #3: Absorption This is accomplished with |
| principles that define soundproofing in any given | | | | simple insulation such as cellulose, fiberglass and |
| situation. There are just a few basic principles that | | | | mineral fiber (wool). Exotic ($$) insulations are also |
| govern the sound isolation of any wall, floor or | | | | available. Foams are not a good product to use |
| ceiling. | | | | for absorbing sound. Foam is excellent for thermal |
| Principle #1: Mass Mass impedes the transmission | | | | purposes, but not acoustic. |
| of sound in a simple way – it's harder for | | | | Installing insulation in a wall or ceiling cavity |
| the sound to shake a very heavy thing than a | | | | increases the sound loss due by eliminating |
| very light thing, no different than saying it's harder | | | | removing/destroying some sound. An important |
| to push a shopping cart full of lead bricks than an | | | | note is that insulation loses its effectiveness at |
| empty cart. However, to make large changes in | | | | very low frequencies. Put some fiberglass in front |
| performance you have to make very large | | | | of a speaker at home and you'll hear the sound |
| changes in mass. | | | | drop. Put that same insulation in front of a |
| Principle #2: Decoupling Think of a typical wall. You | | | | subwoofer and you might not hear any difference |
| have a stud with drywall on each side. If you | | | | at all. |
| hammer the drywall in room #1, that vibration will | | | | Insulation is important, but not very effective if it |
| conduct through the drywall, into the stud, and | | | | is the only technique used. |
| directly into the drywall of room #2, where it | | | | Principle #4: Damping This doesn't mean |
| becomes sound again. This is a very rigid, coupled | | | | moistening your wall. To damp something is to |
| wall, excellent for sound conduction. | | | | reduce its ability to conduct a vibration. A steel |
| De-coupling is very simply disconnecting this rigid | | | | pipe conducts sound well; it is not well damped. |
| connection by inserting a space or something | | | | Drywall, subflooring and most building materials are |
| resilient like neoprene rubber between one layer | | | | not well damped. There are damping materials |
| of drywall and the stud. Products are | | | | known as visco-elastics that can be very easily |
| commercially available to do this such as resilient | | | | and economically applied between sheets of |
| sound clips and resilient channel. | | | | standard drywall and subflooring and are highly |
| If you are dealing with new construction you | | | | effective. |
| should really consider staggered stud or double | | | | Principal #5: Sealing Make sure to caulk around all |
| stud construction for rooms that need isolating. It | | | | openings such as outlets and windows. Seal doors |
| is generally less expensive and higher performing | | | | with weatherstrip. Install duct liner in your ducts. |
| that the commercial products mentioned above. | | | | These all help to keep sound from entering or |
| These techniques all function by inhibiting the | | | | exiting. |
| movement of sound from one side of the wall to | | | | |