There is more than one method for installing mass loaded vinyl to obtain maximum effect. The standard of the industry is to install the MLV directly to the stud or joist framing using an industrial stapler or heavy-duty roofing nails that have the large plastic heads. This method is known as the membrane or septum method. The MLV works well when placed on a wall or ceiling in a membrane fashion, however it can also be sandwiched between 2 layers of drywall or other type of wallboard. The jury is still out on what thicknesses of drywall is best. For better frequency diffusion, it is best to use a layer of 5/8" drywall then the MLV as a septum (a sandwich) and then add a layer of ½" drywall or Homasote. The dissimilar materials do help in the soundproofing effort especially when we are looking to get every STC point we can get with as little effort as possible.
There is not a lot of information on the Web in regards to alternate methods of mass loaded vinyl installation, hopefully we will be able to explore this here.
If you are constructing walls using the staggered stud method, it would be beneficial to actually weave the vinyl in an out of the staggered stud assembly itself. The above picture gives you a rough idea of how this would look. The key to weaving MLV (or any barrier material) is to seal the vinyl as best as possible. In the case of a horizontal weave (most common weave) it is best to overlap the seams by at least 1" and seal that overlap with acoustical caulking as well as a quality seam tape. The weaving of MLV also aids in the defusing of sound waves. This works much like the dissimilar materials except “turbo charges it".
You can also use the weave on a standard stud wall provided there is no drywall installed on either side of the studs. (just open studs) This weaving method can be foiled by stud cross members, so it is best to have only vertically installed studs if you are planning to do the weave. If you weave the MLV on a normally studded wall, there may be problems with the drywall sitting level on the studs. If your studs are 16" on center, then every other stud will have 1/8" of increased width compared to the studs that don’t have the MLV weaved a top of them. To keep the drywall even on both sides, a sound isolation tape can be adhered to every other stud that that is not covered with the weaved MLV this will make all of the stud surfaces flat and even and the drywall will rest evenly on the studs.
From the feedback of our contractors in the field, we have discovered that the more a wood structure is dampened, the better the soundproofing will be in a wall or ceiling assembly. This is especially true for impact noise from above. There are many ways to dampen a wood frame assembly and some are more effective than others. Some contractors have used blown in cellulose in order to dampen the joist or stud structures, but cellulose has no mass and though it will help to a degree, it is much less effective than using blown in closed cell foam, or my favorite (which requires some ceiling demo) is to line the cavity areas between studs and joists with a closed cell vinyl nitrile foam mat (America Mat is a great choice) for maximum dampening. The foam mat would be glued to the studs and the wallboard in the stud cavities (provided you have drywall on one side of the wall only). This insures that the wooden structure is completely dampened and if sealed properly will offer extra soundproofing as a result of sealing those cavities. Sealed dead air space is God’s natural soundproofing method, as I like to call it. I am sure you have read many of the analogies regarding sealed dead air. If you were able to seal the dead air space and actually create a vacuum in that space, you’d be amazed at the amount of sound transmission that would be blocked.
I hope this little narrative helps you especially if you are doing new construction for a home theater, or music sound studio in your home. Thanks for reading and learning together. This is Dr. Bob…..Out!!!!!!