If you are considering a soundproofing project from a 30 story hotel to a bedroom in your home, chances are that you have done some research and are feeling a bit overwhelmed and confused about what really works and how many options you have.
This article is intended to give a clear and concise understanding behind the science of soundproofing coupled with the most popular and cost effective sound deadening solutions. We will keep it short and to the point - if you would like more in depth information just browse our soundproofing articles on the sidebar. We suggest that you read through the entire article once before clicking any links.
How To Stop Sound
Sound is a form of energy that travels as a wave - when that wave hits a barrier as in a sheet of drywall, that barrier will vibrate and cause the air on the other side to vibrate, thus transferring the sound through the wall. There is no one-shot soundproofing technique that will stop noise in its tracks, rather we try to employ a combination of solutions to achieve solid performance.
The four most important elements of soundproofing are:
Absorption can be achieved by installing fiberglass of R-11 in 2x4 walls and R-19 in 2x6 walls and ceilings. Although fiberglass is not a major player, only adding 3-4 points, it is still a step that should be done in any serious soundproofing project. [Read more on insulation soundproofing].
Damping is the process of turning your barriers (drywall, sub floors) into dead panels that do not vibrate, thus preventing sound from passing through them. Damping is achieved by applying a damping compound in between two constrained layers.
Decoupling is meant to separate the attachment of walls from the studs, thereby breaking the direct path of sound, which can be done using resilient channel, and more importantly - with resilient sound clips. This decoupling technique actually adds another component called resilience to the walls. [Click here for an in depth explanation to decoupling ].
Mass simply means creating a heavier wall by using more (another layer) and/or thicker material.
Which Soundproofing Materials To Use
A damping compound is a must on every soundproofing project. The highest performing damping compound is Green Glue Noiseproofing Compound, which can reduce up to 90% of your noise issues alone, and it's performance at low frequency ranges (below STC testing) is remarkable.
There are 3 major players in the resilient sound clip market. Whisper Clip outperforms it's competition by 2-3 points, costs less and is easier to install, saving costs on labor.
At Trademark Soundproofing, we have installed and sold thousands of square feet of sound proofing material. We can confidently tell you that aside from the third party test results, our actual field installation and consumer feedback has shown that Green Glue products outperform any similar products by far.
Creating The Sound Proof Wall, Ceiling and Floor
Walls and Ceilings: The best performing walls and ceilings should be done by installing Fiberglass, Whisper Clips, Hat Channel with 2 layers of 5/8 drywall damped with Green Glue in between.
Excellent results can still be achieved on Walls by just using the fiberglass insulation and 2 layers of drywall with Green Glue on both sides of the wall. This should be given special attention in hotels and multi-family projects, where a double layer of drywall is already in place due to fire rating of the walls. Therefore, it is extremely cost effective to just add a layer of damping compound and achieve solid sound deadening performance.
Floors: For excellent performance, floors should be done in the following order. Floor Joists, Insulation, Gasket Tape, Sub Floor, Sound Board (fiber board), Green Glue and a 2nd Sub Floor. The Ceiling underneath should be done as described above, if possible.
Existing Walls and Ceilings: Additionally, you can install another layer of drywall with Green Glue in between, on existing walls and ceilings. For better results, it can be done twice (double up). This is really one of the only options available when dealing with existing walls. For more details see our article Soundproofing Existing Walls and Ceilings.
One important soundproofing tip to remember is to always seal your perimeters and electrical boxes, etc. with a high quality acoustical caulk.
Doors: Doors and windows are weak links in any sound proofing project, fortunately you can still have a decent door at an affordable price. The simplest solution would be to use our custom cut Sound Control Door Panel. If you would like to use your door on its own then follow these tips. Use a solid wood door, if looks are not an issue install a layer of drywall or wood over the door with Green Glue in between (try getting a flat door). Use proper Door Gasketing and a Door Bottom to seal the door completely. As doors have gaps on the sides and bottom sealing is very important when dealing with doors. Before you put your molding up stuff the gap between the door and wall with foam or sound proof rubber. For more info see this Door Soundproofing Article.
What To Avoid
- Do not place resilient sound clips and/or channels over existing walls, as this will cause what is known as the triple leaf effect.
- Factory damped drywall is very expensive, more difficult to hang and does not perform as well as the Green Glue damping compound. The reason for that is simply because Green Glue is a better compound and is installed in a heavier wall.
- Soundboard and/or resilient channel in walls and ceilings do not perform up to par, as anyone who has installed them can attest to. You will get just as much or more by installing another layer of drywall.
- Expensive floor underlayments are also a source of post customer complaints, avoid them and use cheap sound board for better results, get the most out of your floors by adding Green Glue in between, as stated above.
How Is Noise Tested?
Let's take a look at a very popular term called STC (Sound Transmission Class) which is an industry standard to calculate sound transmission through barriers. Many building codes now require condos and townhouses to meet a STC of 50, luxury hotels and condos should be looking to reach 60 and higher.
|20-25||Very Poor||Low speech audible|
|25-30||Poor||Normal speech understood|
|30-35||Fair||Loud speech understood|
|35-40||Good||Loud speech heard, but hardly intelligible|
|40-50||Very Good||Loud speech heard faintly|
|50-60||Excellent||Loud sounds barely heard|
A standard 2x4 wood stud wall with 1/2" drywall has an STC of 32. An important point to keep in mind is that STC testing only tests on frequency ranges from 125 - 4000 Hz. One problem with this type of classification is that a lot of the common noise issues are due to sounds that fall below or above this range. Examples of such sounds are bass drums, deep male voice, trucks, etc. - all of these can start at 50 Hz. High pitched female voices, shrill ringing of phone and auto horns are good examples of sounds that reach above the 4000 Hz range.
This will explain why many big projects, after having paid tens of thousands of dollars for acoustical engineers and getting thousands of pages of tested soundproofing materials with lab testing of STC of 50 and above, still receive complaints for poor acoustical performance. Just look at this long list of sound complaints from seasoned hotel travelers.
For good measure we will add one more reason for poor performance results: the fact that although material can test to a STC of 25 for instance, does not mean that when added to a wall assembly of 32 (like a standard 2x4 wall) that the end result will be a STC of 57 (25+32=57). In reality, it may only add 2-3 points to the wall bringing it to a STC of 35. A perfect example of this phenomenon is the much touted Mass Loaded Vinyl and all the other brand names that it is sold under.
Here at Trademark Soundproofing, our results are based on actual field installations and customer feedback. As you can see, the basics are simple and straightforward with less cost than you might have anticipated. There are some fine tuning details which you can still pick up by browsing our site or by contacting one of our friendly associates.
When you are ready to begin the actual process of sound proofing click on our soundproofing 102 How to Soundproof article, for detailed instructions.
© 2009 by Trademark Soundproofing