Construction Techniques for Sound Dampening

Soundproofing in construction is advanced in every detail. Calling your usual handyman to help with some sound attenuation is going to go nowhere. This niche resides in the hands of a small and elite group of engineers, whom for the most part (compared to other areas of construction), have published very little for the rest of us web surfers to dive into. I’ve arrived at my understanding of soundproofing through a lot of trial and error over a 15 year period. Living on busy streets, living with annoying room-mates or just having a compulsive need to bang my subwoofer whenever I wanted, are just a few scenarios that pushed me towards seeking soundproofing solutions. This journey has been a steady one for me and I’m willing to bet as our cities grow bigger, tighter, and more diverse, the soundproofing challenge will be a reality for many others as well.

First, let’s commit to the term sound dampening because soundproofing just isn’t going to happen. It’s not that it isn’t possible; it’s that it ‘s extremely unlikely, so we will focus instead on some modest budget construction details that are within the scope of most contractors.

Sound dampening comes down to a couple keys factors. To be brief, they are decoupling and mass. Let’s flush that out: If you live in a regular North American home, constructed of timber framing and skinned with drywall, then sound transmits quite easily across walls and through floors. The reason is that sound energy (which travels in waves) moves most easily from one material to the next when those materials are attached to each other. For instance, drywall attached to framing attached to drywall; if materials are not touching then the transfer of sound waves will be seriously reduced. This is called decoupling. The concept of mass refers to the fact that sound waves have a more difficult time vibrating through a heavier partition. Increase the mass significantly, increase your sound isolation. Stick with me and I’ll walk you through some proven techniques to isolate your audio pleasure:

Retrofitting an existing room is always more challenging, therefore let’s approach our material breakdown from a new construction perspective. When building from scratch, with sound privacy in mind, you should at the very least fill the wall or floor cavity with “SAFE’n’SOUND ” batting insulation; This will help considerably. Now if you are more committed to the process, next I would suggest upgrading the normal 1/2″ drywall to 5/8’s thickness. Personally, I find this upgrade delivers a very noticable degree of improvement. Remember I’m not an engineer so I will not provide measurable STC (sound transmission class) or decibel specifics here. I am just speaking from real life experience based on what I have experimented with.

Now for those of us who are willing to go further and ramp this construction game up another notch:

Resilient Channel

I have built walls in a couple different ways with more articulate detailing to defend against this problem of sound bleeding. The first is installing resilient channel on the studs or joists before hanging the 5/8’s drywall from it. If you fasten the resilient channel to every other stud and then stagger that fastening for each channel that is installed, you are decoupling the finish surface (drywall) from the wall structure (wood studs) about 50%.This provides a marginal improvement … but nothing impressive in my opinion.

 

The next addition that is worth every penny and time investment is doubling up the drywall. This can be done in whatever thickness you prefer but remember the thicker the better (recall mass). Do this on both sides of the wall and you are protecting yourself quite well.

The following 2 options are for those construction enthusiasts who love playing with new materials or those who are dead serious about playing Celine Dion early in the morning with no volume limitations. The first assembly has delivered solid results in my personal experience but is more expensive so requires commitment. The wood studs or wood joists first receive “Genie Clips”. The “Genie Clip’s” rubber body greatly reduces the transmission of sound waves from one material to the next.  That “Genie Clip” is what holds the resilient channel, which then holds the drywall.  Installing these “Genie Clips” in a staggered format to the studs greatly reduces the coupling of material layers. Overall I find the inclusion of the Genie Clips in your wall assembly very beneficial towards sound transmission dampening.

Genie Clip          genie-clip (2)                 Green Glue Caulking

Now you have built this assembly and are looking at finished drywall. Many people would stop there and start the mudding of the drywall joints. But wait, for approximately $20.00 per tube you can spread a product called “Green Glue” caulking on that drywall and install a 2nd layer of drywall on top to achieve some very serious results. Make sure to stagger all joints of the drywall layers. At this stage your room has been dampened acoustically by decoupling to a certain degree, layering significantly, adding mass, and separating that mass with viscoelastic caulking.  What that means is sound waves coming in to contact with this wall are up against a plethora of transitions, each of which take a shot at that wave’s intensity, thereby weakening it greatly by the time it reaches the other side.  

 

An Alternative

Another great option which removes many of the above layers is the double wall construction.  This is exaclty what you think it is and generally is not practical for people since it consumes so much square footage. That said, it is very effective. Basically frame a 2nd wall inside the existing 1st wall, insulate, and finish it however you want.

Consider Windows

This is another animal all together and seems to be even more difficult for home owners to get support from manufacturers, glass companies or industry experts. From what I’ve gathered it connects very strictly to IMG_0955.JPGthe mass of the glass being used and if possible, you want to get yourself laminated glass. That’s the decoupling component where 2 panes of glass are sandwiched together around a plastic film of some sort. The thicker you get, the better your results. Then add another one of these with an air gap in between (a minimum of 5″) and you’re in the big leagues.  Keep in mind that those two assemblies should not be sitting in or on the same framing material. They should be separate from each other in order to decouple.  So the casing in the window’s rough framing should not be monolithic. I repeat…decouple structure everywhere you can.

 

It doesn’t get any briefer than this break down of sound dampening construction. The field tends to be very technical and science heavy so I’m trying to break it down in layman’s terms for your straight forward construction. Good luck!