Thursday, June 30, 2005

Sound clips VS Resilient channels

We get many questions regarding the differences between Sound clips and resilient channels or RC's In a previous post to this blog I discuss RC-1 and it's installation. It is the most common product used for floating a ceiling or wall, however the margin for error with this product is incredible and we have heard more horror stories about RC than any other soundproofing product on the market today.
Sound clips (or as we call them, Americlips) are specifically designed to work in conjunction with the 7/8" metal furring channels. The margin for error is this product is greatly reduced.
Basically a sound clip is an isloating device that is attached to the structure (studs or joists) via screws, generally drywall screws. There are many different types, one in particular, the PAC RSIC-1 can be installed to the structure first and then the furring channels fitted afterwards. The Americlips must be attached to the furring channels first and then the entire assembly installed to the structure as one unit. The Americalips attach with 2 screws while the RSIC-1 attaches with only one screw. Both clips have their advantages and disadvantages. The RSIC-1 can be installed parallel or perpendicular to the studs or joists, but the Americlip due to it's design of having a 2 screw connection can only be installed parallel to the studs or joists and the furring channels will be held perpendicular to the joists or studs. In my opinion the Americ clip is a more stable device simply due to the dual attach points. Both products offer over twice the soundproofing of common RC-1 or RC-2 (which is used for ceiling mostly). If installed properly, a floated ceiling using RSIC-1's or the Americlips can offer an STC rating of upwards of 38STC. There are some other products that can be added to the assembly which would increase this STC value greatly.
Installing a layer of Mass Loaded Vinyl on the ceiling or wall first would add upwards of 26 STC points to the ceiling or wall assembly. The use of mineral wool or rockwool (Roxul) between the rows of soundclips and furring channels will also be helpful in increasing the STC rating of the wall or ceiling you are soundproofing. The sound clips only lower the ceiling by 3" or less.
Here is basically what the sound clips and furring channels are accomplishing in a floated ceiling for example. They combat the impact noise from the unit or room above by breaking the sound
transmission circuit of the impact of walking and or dropping things. This impact noise is stopped at the connnection point of the sound clips to the ceiling joist assembly. There is a rubber insulator on the sound clips that breaks the joist or stud impact transmission.
As for the airborne noise such as stereo's, TV's telephones etc. the resilience of the ceiling is such that when these sounds come down from above or even try to go up from the unit below, they vibrate the resilient floated ceiling's drywall, and the sound is unable to pass through the drywall and disappates rapidly. The installation of mineral wool or rockwool between the rows of sound clips and furring channels prevents both the impact and the airborne noise from flanking into adjoining wall structures.
In any floated assembly there is also a 1/4" gap that must be maintained around the entire perimeter in order to keep the ceiling isolated from the adjoining walls. This gap is filled with a resilient acoustical caulk which will both add to the soundproofing and maintain the resilience of the floated ceiling. The gap can also be filled with a closed cell foam backer square which is adhered to the edge of the drywall on the sides, that would usually meet with the adjoining walls. The backer square must however still be caulked to maintain a seal at the drywalls edge as well as to maintain the resilience of the floated ceiling assembly. Sealing in the soundproofing game is essential.
A well floated wall or ceiling is a quality of life issue. The sound of footsteps or voices from above can make you feel that your neighbor is actually living with you in your unit. We all want our privacy and floating a wall or ceiling properly can give us just that!!
I welcome your comments, and if you have any questions about floating a ceiling or wall, or any soundproofing questions at all, please feel free to e-mail me or call Soundproofing America. Thank you.

Dr. Bob

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