| Room-to-room noise reduction is rated in terms of | | | | into the structure. |
| sound transmission class (STC). The acoustical | | | | Actual Performance |
| performance of common 16" OC wood stud walls is | | | | There is one test from an independent lab showing a |
| typically STC 30 to 34, and 24" OC wood stud walls is | | | | branded mass loaded vinyl at over STC50 on a 24OC |
| STC 36 to 39. This is considered poor, as | | | | wood stud wall. Unfortunately that test was conducted |
| conversation can be easily heard. An older method to | | | | on a single wall section (4' x 8') rather than the required |
| improve wall isolation since the 70's is a product called | | | | 8' x 12' wall, thus rendering the test invalid as it does |
| mass loaded vinyl. It is sold under a number a brand | | | | not meet the requirements of ASTM E90. Three other |
| names, such as AcoustiBlok, SoundBarrier and others. | | | | full scale tests have now been published which show |
| Other methods include soundproof drywall and resilient | | | | MLV on one side of a 24OC wood stud wall at STC |
| channel. Each has advantages, some of which we will | | | | 43 to STC 45. This is an improvement of about 15% |
| compare. | | | | less noise as heard by humans. |
| Acoustics and Vinyl | | | | RC tests are prevalent as it has been used often |
| Noise can be attenuated with additional mass and | | | | since 1963. As are soundproof drywall tests (on the |
| many companies make vinyl sheets weighing about | | | | Quiet Solution site). It is always recoemmended to |
| one pound per square foot. For this type of acoustical | | | | review testing from third party accredited labs that are |
| treatment, the mass of the materials is the dominant | | | | full-scale walls. |
| factor. However a wall already weighs 4 to 5 pounds | | | | Cost Considerations |
| per square foot before mass loaded vinyl is added, so | | | | One pound per square foot vinyl sells for $1.50 to |
| the extra pound added by a single layer of vinyl is only | | | | $2.00 per square foot at many online stores plus |
| a small amount of added mass. | | | | shipping (add about $1 per pound for UPS). So the |
| Vinyl sellers display transmission loss data of bare | | | | delivered material cost averages $2.50 to $3.00 per |
| sheets showing an STC of 26 or more. However | | | | square foot. |
| presenting bare product performance is not related to | | | | Vinyl installation is labor intensive. The vinyl needs to be |
| the performance in an actual wall. The acoustic ratings | | | | unrolled, cut by hand around obstacles, attached with |
| of individual materials cannot be added to existing | | | | fasteners and carefully taped along every seam prior |
| walls. For example, a single sheet of 5/8 inch thick | | | | to the installation of the drywall layer. If one is not doing |
| gypsum board by itself has an STC of 28 --- 2 points | | | | the work themselves, subcontractors charge $1.00 to |
| higher than that of one pound vinyl. But you cannot add | | | | $2.10 per square foot for installation. |
| that 28 to a wall of 30 and get 58. In fact, an extra | | | | Thus, in reasonable sized projects, one can expect an |
| layer of gypsum adds only 2-3 STC points to any wall. | | | | increase in wall costs of $3.50 to $5.10 per square |
| Adding mass to a wall follows mass-law which states | | | | foot. Consider a base of about $4.00/sqft if it is new |
| that a doubling of wall mass adds about 5 to 6dB of | | | | construction for the studs, gypsum, and standard labor, |
| isolation. That is, a doubling of mass of the entire | | | | and this results in a wall that averages $8/sqft. This will |
| structure! | | | | result in an STC 43 wall assembly with 24" OC studs. |
| When considering any product for soundproofing it is | | | | Comparison |
| imperative to look for independent lab tests on full | | | | Soundproof drywall products such as QuietRock, |
| scale 8' x 12' walls performed to a current ASTM test | | | | create a damped structure. Lab tests on soundproof |
| method (ASTM E90 and E413). Remember individual | | | | drywall show STC's of 50 or better when used on |
| STC values do not add up. | | | | one side of a 24OC wood stud wall. This material |
| Resilient channels is also an older soundproofing | | | | replaces one side of drywall, saving money and time. |
| technique, dating back to 1963. It uses isolation (floating | | | | Low cost soundproof drywall today runs about $1.20 |
| the wall) to achieve improved STC results. One is | | | | sqft (and is available at local dealers). Labor is about |
| required to make suire the drywall does not touch the | | | | $0.60/sqft. Thus total wall costs can be under $5.30 |
| adjacent walls, floors or ceiling. However STC's of 45 | | | | per square foot depending on performance required. |
| to 48 can be achieved in this method. While difficult to | | | | No special training or labor is required, since it installs |
| actually assemble accurately in the field, RC's are | | | | just like drywall. The resulting performance is a 50% |
| inexpensive and can be used for light soundproofing. | | | | noise reduction (versus 15% for vinyl), the overall cost |
| Soundproof drywall is just as it says. It is an internally | | | | is 30% lower. |
| damped drywall product which requires no special | | | | Resilient Channel is another technique which has been |
| assembly methods. Simply hang it in place of standard | | | | used since the 1960's. This requires hanging metal |
| drywall and one can achieve STC's higher than 50 on | | | | channels on the studs and then hanging drywall on the |
| a standard single stud wall. The material does cost | | | | channels. The drywall must be isolated on all sides |
| more than standard drywall, but the overall labor is less | | | | since touching the floor, walls or ceiling could |
| than other methods and the reliability is high. | | | | acoustically "short out" the floating wall and reduce the |
| Sound Transmission in Walls | | | | performance. |
| In a single stud assembly, the major path of sound | | | | If done right, with a double drywall on the RC side, and |
| transmission is directly through the studs rather than | | | | no shorts, it is reasonable to achieve an STC 48. The |
| the air in the cavity. The addition of a vinyl layer does | | | | cost of this wall is under $6.00/sqft including labor. |
| little to change this since the outer gypsum will be | | | | While the performance is less than soundproof drywall |
| nailed or screwed directly through the vinyl into the | | | | and the difficulty is higher, it is a mature method which |
| stud. For significant improvements, one must change | | | | was popular before the advent of soundproof drywall. |
| this path fundamentally, or introduce specific damping | | | | So it may be worth still considering as an option. |