Common Soundproofing Materials and How to Soundproof a Room
What is everything for? There are many different materials used in sound proofing. Some of these materials are readily available and fairly affordable. Others are proprietary and have “hidden” specifications and/or design characteristics and are usually expensive. Beware, it is often the expensive proprietary materials which also come with the most outrageous claims. In reality it is possible to achieve good soundproofing with readily available and inexpensive materials if you know what you are doing.
How much does it all cost? It is very difficult to put a budget on soundproofing. There are a lot of variables like where you will be purchasing your materials from, how much material you will need, the sort of surface that you be working on and so forth. If you are doing it yourself, perhaps a rule of thumb is total cost will be twice the price (per square foot or square metre) of the main material which you are using. In other words if you are using a material which is $5 per square foot you might want to budget $10 per square foot to do the job. Obviously the second $5 goes towards other components of the soundproofing. This is just a very rough rule of thumb and it assumes that you are not factoring in any labour costs.
Which ones do I really need? A quantity of a material is considered to be cost effective if it offers a good measure of soundproofing at a relatively low price compared to other materials or compared to a greater quantity of the same material. So there is every chance that you might have heard of a perfectly good soundproofing material which is not discussed here. If you were to put together a basic list of soundproofing materials it might include the following:
- Drywall/plasterboard and possibly mass loaded vinyl
- Flexible acoustical caulking & a caulking gun
- Laminated glass
- Solid core doors
- Resilient fixings e.g. furring channels
- Basic timber frames
Which soundproofing materials are the easiest to work with? Unfortunately most soundproofing techniques and materials require a bit of effort. The secret to success is to take your time and to read as much as you can about best practice installation. For example plasterboard (drywall) installation is fairly straightforward if you do it recipe style. On the other hand if you try to make it up as you go along you will probably create an unsightly mess. Again the materials and techniques presented here are the ones which are considered to be suitable for DIYers while also effective for relatively inexpensive soundproofing.
Which soundproofing materials are the most effective? The effectiveness of a material or technique will very much depend on the quality of the installation. The key things to watch for are:
- Avoid any rigid fixings like screws and nails and use resilient mountings wherever possible.
- Ensure everything is airtight.
- Pay particular attention to any joints and ensure that they are properly caulked.
- Ask yourself what will happen to the effectiveness of your soundproofing system at any edges or junctions.
- Is it possible for sound to “flank” or travel around your newly constructed barrier?
- Sometimes you will need a strategy to deal with this “flanking noise”.
- The easiest flanking strategy is to continue the soundproofing technique beyond the edges of the surface in question onto the adjoining surface eg ceiling to wall and vice versa.
The theoretical effectiveness of a material is usually presented as a sound absorption or sound reduction measure, also expressed as sound transmission and noise reduction classes (NRC & STC). There are many tables available with these measures for all sorts of materials. The purists will tell you that these figures mean totally different things and should not be interchanged. This is true but in many ways it is not something the DIYer should be concerned about. Here is a quick way to interpret the figures: over 30 for good individual materials and over 50 for a good complete soundproofing system.
If a material is a sound absorber like fibreglass batt insulation or open cell soundproofing foam, try to place it near the source of the sound, not in the room receiving the noise. If you can only work in the room receiving the noise pollution then stick to sound barriers, also known as sound reflectors. Note that fibreglass insulation is a poor sound barrier (low STC) but has a good noise reduction coefficient (NRC) when used at the source of the noise. It is important to keep the terms “noise source” and “receiving” and “absorption” and “barrier” top of mind when you review the comments on the materials below.
If the material is clearly a rigid or dense material then the comments are likely to be referring to its performance as a sound barrier placed in the room receiving the noise pollution. If the material is porous, flexible, or of quite low density then the comments are likely to be referring to the material as a sound absorber placed near the source of the noise.
Naturally there are a number of exceptions to these descriptions. Below are some examples of absorbers and barriers. Clearly many materials are hybrids and have both characteristics.
Obviously you will be shopping for inexpensive materials with good noise reduction properties whether as barriers or absorbers. You might find an expensive material which is being dumped at a good price or you might live in a part of the world where a material is in ready supply and so is less expensive. Be a little bit lateral when you start shopping and planning.
Another important consideration is the frequency of the sound that you are trying to attenuate. Generally most materials perform more poorly for lower frequency sounds like drums or boom cars or stereo subwoofers. If the sound is low-frequency try to use more dense and or thicker materials. Again as a rule of thumb if you always prepare your designs for low-frequency soundproofing you will invariably solve your high-frequency soundproofing issues as well.
Absorbers
1) Rolls of building Insulation
As expected building insulation is a very good sound absorber at the source of the noise. The thicker and more dense mineral products are superior. Performance can be improved by introducing an air space in the total design of the soundproofing and also by using insulating materials with a lining – where the lining faces the sound source. Building insulation tends to be more effective for soundproofing around the frequency of human voice. The most cost effective thickness for roll insulation is probably 3 1/2 inches or just under 9 centimetres.
2) Batts
As for rolls of building insulation.
3) Rigid fibreglass sheets & ceiling board
Again generally the thicker the board the more effective it is. Probably the most cost-effective thickness for fibreglass board is around 2 inches or 5 cm. Interestingly fibreglass boards with facings seem to perform less well than fibreglass boards without facings. In other words avoid the added expense of faced boards.
4) Form board for roofs
Two to 3 kg density fibreglass form board of only 1 inch thickness is easy to handle and performs very well if you are able to obtain it at a good price.
5) Ceiling boards
Painted perforated and fissured mineral ceiling board is easy to handle and performs reasonably well at around 2 cm thickness. The best soundproofing is achieved with cast rough texture mineral ceiling board. Note: wood fibre ceiling boards do not perform particularly well. Foam sheets/tiles and soundproof foam ceiling boards perform quite well as absorbers when they are one or 2 inches thick. At this thickness they perform almost as well as the mineral ceiling board, but are clearly much easier to handle. Mineral ceiling board probably has better barrier qualities though.
6) Wall panels
For the general principles relating to wall panels see the comments on ceiling boards.
7) Floor coverings
Carpets are only good soundproofers if they are used as absorbers. A lot of their effectiveness comes from reducing impact noise. So for example you might put down carpet mostly to reduce the sound of footsteps on a timber floor and to dampen some of the airborne noise in the room. There are specialised underlays which can be placed beneath carpets or floating floors. These need to be properly selected and you should ask for very clear sound transmission performance data and additional data on impact noise performance.
8) Brick
People are usually surprised to learn that bricks are sound absorbers rather than sound barriers. They are even more surprised to discover that brick is a relatively poor sound absorber. Notions of very quiet brick homes usually come from older double brick construction were an air cavity between the two skins of brick contributes significantly to the overall soundproofing effectiveness.
9) Other
There are arguments around about whether materials like plywood, drywall and glass are absorbers or barriers. Here they are referred to as barriers and they are outlined in the next section. Do not worry about the various proprietary laminates of absorbers they are not worth the money. Moreover you will usually get a better effect if you purchase the two layers un-cemented and install them separated by a few inches of airspace and perhaps secured by some sort of resilient fixing. The small airspace between two absorbers seems to add quite noticeably to soundproofing performance. Spray on cellulose can be a useful absorber however there is no guarantee of what you will be getting or how thick it will be. Properly applied it can be an excellent material to use in roof cavities for thermal and acoustic insulation. It can be sprayed directly onto the underside of the roof board or shingles or tiles.
Barriers
1) Glass & Acrylic sheets
These options perform about the same at equal thicknesses. The most cost effective thickness being around of an inch or just over 6mm. Rather than using thicker material it is advised that you create a sealed air cavity between a couple of sheets of the material.
2) Plywood
Plywood is not quite as effective as drywall but is obviously stronger and less fragile. The most cost effective thickness for plywood is probably half inch or about 13mm.
3) Drywall, Gypsum board or Plasterboard
The performance of drywall does not seem to improve very much between 1/2 inch and 5/8th inch thickness, so the most cost-effective thickness is obviously half inch. When you use multiple layers of drywall it’s important to secure them with some form of resilient fixing, this considerably improves the soundproofing characteristics.
4) Mass Loaded Vinyl (MLV) & Fiberglass Reinforced Plastic Panels (FRP)
MLV & FRP are highly effective and easy to use products as they can have a thickness of only a fraction of an inch. The downside is that they can sometimes be expensive. A roll of MLV with a density of 1 pound per square foot or about 5kg per square metre is as effective as half inch drywall and 1/8th inch (3mm) FRP. If you can buy MLV or FRP at about the same price as drywall you might consider using them instead. You could even consider using MLV or FRP behind a second layer of drywall to create super soundproofing without increasing the thickness of the wall too much.
5) Concrete Panel
This is not really an option for most DIYers however if you are looking at buying an apartment make sure the walls are at least 4 inches of concrete plus drywall or 6 inches of concrete if it is an unfinished surface. Six inches plus drywall finishing should give you the same soundproofing as a double brick and cavity construction.
6) Laminated Products
Again there is little justification for purchasing laminated products. For about the same cost, better performance can be achieved using the individual components resiliently mounted with a small air cavity.
Do You need to buy any special proprietary products? The simple answer to this is no. You will come across lots of advertisements for groundbreaking scientific innovations in soundproofing. It’s possible that one day something will be invented that will be inexpensive and highly effective but for the moment most proprietary products perform no better than readily available combinations of inexpensive materials.
An important note on resilient channels: Having said that it is not essential to buy proprietary products, the resilient Channel is probably one material that you should select more carefully and which may be worth restricting to specific brands. You should look for a product made from 25 gauge steel ideally with some form of STC guarantee. Channels can have one or two legs and usually have slits or cut outs along their length, these are design characteristics which add to the resilience of a material.
When installing resilient furring channel on a wall, if it is the type with an open flange, face the flange upward so that it is pulled away from the frame slightly when the wallboard is attached. Point all the flanges in the same direction whether on a wall or ceiling. Take great care when installing the wallboard to the channels so that you do not “short out” the channel by screwing too far through the channel and into the timber behind.
Published by Craig Williams (2012)
EzineArticles Expert Author
For more information on inexpensive home soundproofing visit http://www.SoundProofingSecrets.com
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