I’m finally getting around to finishing the basement now that the kids are big enough to want their own rooms. I wondering if it would do any good to fill the space between floor joists with insulation to help stop sound transfer to the upstairs.
There are many choices on the market, but my budget is tight. So, what would be the best soundproofing insulation for my needs? I put together a list of possible options:
- Mineral Wool
- Blown-In Cellulose
- Spray Foam Insulation
- Foam Board
With the list in hand, I took a closer look at the different types and what they do. If you want to know more about any of these options keep reading as I give my insight into every single one.
- Typical Types of Residential Noise Problems
- Understanding the Basics of Sound Transmission
- Insulation & Noise Reduction
- Types of Soundproofing
- Different Types of Insulation
- Mineral Wool Soundproofing Insulation
- Fiberglass Insulation
- Sound Deadening With Blown Cellulose Insulation
- Soundproofing with Spray Foam
- Using Styrofoam Insulation for Soundproofing
- So, What Type Of Insulation Is Best For Soundproofing? Comparison
- Tips for Using Insulation to Soundproof a New Building
- Other Ways to Soundproof Your Home
Typical Types of Residential Noise Problems
In most residential areas there are thousands of noises. They can be airborne, impact or flanking sounds. The type of noise and its frequency range are the factors that bother us.
Our hearing range is between 20 and 20,000 Hz, and it’s most sensitive to sounds in the 1000 Hz range. Sound insulation can help improve our comfort and even our health.
- Airborne Sound
Airborne sounds are noises that move through the air. Vehicles honking, radios, conversations, or dogs barking are examples of airborne noises.
- Impact Sound
Impact sounds are noises caused by something striking something else. For example, a toy or glass falling on the floor or people walking on a hardwood floor are impact sounds.
- Flanking Noise
Flanking noises are sounds that travel through, under or over a sound barrier. They are the most difficult to control as they take an indirect path. Sound waves can travel through ductwork, over or under the best soundproof wall, and through hollow core doors. Sound can even transfer through back to back electrical boxes!
Understanding the Basics of Sound Transmission
Sound travels through the air in different wavelengths. Wavelengths are measured from crest to crest or trough to trough and represent different sounds. The distance between crests or troughs represents different frequencies of sound.
The farther apart the crests the lower the frequency and the closer together the higher the frequency. Wavelengths we can hear are between 0.67 of an inch (17mm) and 55.77-feet (17m).
Frequency is measured in Hertz (Hz) and represents the tone (frequency) or musical value of a sound. A flute has a high pitch of 2,000Hz and a tuba a low pitch of 29Hz. Most of us start out able to hear between 20 and 20,000Hz, as we age it becomes less.
Pitch is the sound frequency created, and the tone is the frequency we hear. The same frequency can be generated by different objects and produce different tones.
When a sound wave encounters a wall or objects it could be absorbed, reflected, refracted, diffused or diffracted, or transmitted. To control sound in a house, we want to either absorb part or all of a sound wave or block it so noise transmission doesn’t occur. The properties of different insulation material allow it to absorb sound or reduce its transmission through that material.
How loud a sound is, is measured in decibels or dB on a sound pressure scale. 0dB is the beginning of what we can hear, and 130dB will cause physical pain. A quiet home will be in the 40dB range.
There are several different scales used to measure the effectiveness of soundproofing materials. STC is the Sound Transmission Class, and NRC is the Noise Reduction Coefficient.
Understanding STC and STC Ratings
STC (Sound Transmission Class) is a method of comparing how well windows, doors, floors, walls and ceilings are at reducing sound transmission. It measures the decibel (dB) decrease as sound passes through or is absorbed or blocked by material or wall.
STC use began in 1961 and measures the sound decrease, or transmission loss (TL), of 16 common frequencies between 125Hz and 4,000Hz through a wall or barrier in your home. The results are graphed and form a curve.
Your curve is compared to a set of standard STC reference curves. The reference curve closest to your curve is your rating. The higher the STC rating, the better the wall or material is at blocking or reducing the noise transmission of the frequencies tested.
Measuring Sound Transmission
To measure the sound transmission of a barrier or room, 16 common frequencies are generated in one room and measured, the sound is also measured on the other side of the wall (outside the room). The difference in sound transmission results is graphed and compared to a standard set of curves. The result is the STC rating.
Recommended STCs for Your Home
A quiet home has an STC 40 rating. The International Building Code (IBC) recommends a rating of STC 50 for walls, ceilings, and floors as a minimum requirement. An increase to STC 55 or STC 60 would be better.
For residential locations, an STC 52 for bedrooms and STC 56 for bathrooms, living rooms and kitchens, are recommended minimums. A 2×4 wall with ½” of drywall on both sides, but no insulation, has an STC 33 rating.
NRC (Noise Reduction Coefficient)
The Noise Reduction Coefficient (NRC) measures the amount of sound a material absorbs or reflects on a scale of 0 to 1. No sound is being absorbed or reflected at 0, and all sound is absorbed or reflected at 1.
It is based on 4 frequencies of 250Hz, 500Hz, 1000Hz, and 2000Hz which are the typical range of speech. It is rounded to the nearest 0.05 increment.
The NRC is often listed as a percentage based on its decimal. Drywall with paint on it has an NRC rating of 0.05, which means 5% of the noise is absorbed and 95% is reflected.
SAA (Sound Absorption Average)
The SAA is a sound absorption average with a rating similar to the NRC. Instead of 4 frequencies though, it uses 12 one-third octave bands in the 200Hz to the 2500Hz range.
It is presented as a value between 0 and 1, with 1 being 100% absorption of sound. It is rounded to the nearest 0.01 increment.
SAA and NRC can achieve values higher than 1.00 if the material being tested has large air spaces or is thicker than normal.
Insulation & Noise Reduction
When designing, building or renovating a building, or finishing a basement, it is important to include soundproofing in your walls and ceilings. There are three ways to reduce or prevent the sound transmission through walls at the time of construction.
Increase the mass with an extra layer of drywall, break the vibration link between rooms and improve the cavity absorption – or all three.
Standard insulation products absorbs some sound, and acoustic insulation absorbs more. However, insulation also reduces the reverberation which causes a sound to echo or bounce back into a room creating disturbing feedback. The insulation will reduce sound transmission through the wall, and also improve the sound within a room.
A typical interior 2×4 wall with 1/2” of drywall on both sides has a rating of STC 34.
Adding standard fiberglass insulation improves the rating to STC 39.
Adding sound rated insulation can improve that to STC 45.
Building the same wall using 2-1/2” metal studs with 1/2” drywall on each side you get an STC of 34; add same sound rated insulation can bring the rating to STC 47.
Using 5/8” drywall instead of 1/2” on the steel studs brings the sound insulated wall up to STC 49.
Types of Soundproofing
There are different ways to improve the sound (STC) rating of your home during the construction stage. Each will work independent of the other, but they achieve better results when working together.
- Sound Absorbing
Materials that absorb sound reduce or prevent noises from bouncing back into a room or going through barriers into other living spaces. They’re usually lightweight and porous and trap soundwaves.
- Sound Blocking
Sound blockers are usually thick, hard or heavy materials (they can also be flexible) that prevent or reduce nise transmission through walls, floors or ceilings. Their mass reflects sound and prevents it from entering or leaving a room and is usually installed in ceilings, floors, walls, and even doors.
- Sound Damping
Sound damping reduces or prevents vibrations from traveling through walls, so they can’t transfer noise, or as much noise, into other living spaces.
- Sound Decoupling
Is a construction method that decouples or separates one wall face or side from the other or the drywall from the framing. Staggered or double stud framing, the use of isolation clips or channels, are ways of reducing or preventing sound transfer between rooms.
Different Types of Insulation
Mineral wool is a spun fiber made from molten igneous stone or slag. It is incombustible and doesn’t absorb water.
It is a dense and porous material that slows the movement of heat and cold through walls, floors and ceilings. Additionally, it can absorb both airborne and impact sounds and vibrations.
Fiberglass is made of melted plastic spun into wool and reinforced with tiny fibers of glass. It is a porous material that traps air helping to keep a room warm or cool depending on the season. It absorbs airborne sound at similar levels to mineral wool.
Blown-in cellulose insulation is made of 75-85% recycle fiber from paper, with the remaining 15-25% made of a fire retardant material. The more loosely packed the fibers, the better their ability to absorb and dampen sound. It can be added to post construction partition walls much easier and cheaply than other materials.
Spray Foam Insulation
Spray foam insulation is a polyurethane foam spray that makes a thermal barrier and minimizes air movement. It’s great for keeping the cold or heat in or out, but not a good sound absorber. There is however a sound control spray foam that works well as a sound blocker that can be used in post-construction walls.
Foam boards, whether blue or pink, are made from extruded polystyrene. The color represents two manufacturers. They are board rigid with an insulating factor of R 5 per inch of thickness.
Expanded polystyrene foam panels don’t insulate as well, and are more brittle or fragile. Polyisocyanurate (ISO) panels are also extruded, and better at insulating than the pink or blue panels, but more expensive.
Polystyrene boards can help reduce sound transfer and muffle sound in or out of a room by decoupling the layers.
Mineral Wool Soundproofing Insulation
High Performance Mineral Wool
High performance mineral wool is lightweight insulation with improved thermal and acoustic properties. It is manufactured from a mix of mineral wool from molten rock and slag, and combined with new glass wool process. It has improved sound damping and absorption properties.
With sound absorbing ratings of 95% and NRC of 1.05, high performance mineral wool provides improved sound reducing values. Much lighter in weight provides equitably with twice the density of multi-purpose mineral wool.
Use in select interior walls or ceilings and floors to reduce sound transfer, feedback, and echo. I’d recommend using the high-performance mineral wool insulation in the walls and ceiling of multi-media rooms and high conversation rooms like the living and dining room.
It will reduce sound transfer between rooms and add density to the walls to minimize feedback and echo making it easier to hear clearly in the rooms.
Multi-Purpose Mineral Wool
Multi-purpose mineral wool insulation is composed of spun fibers created from molten rock. The fibers make it more fire, moisture, water, and rot resistant.
The high-density multi-directional fibers also give it good acoustic qualities. It can be used for interior or exterior walls and has an NRC ratio of 0.852.
All mineral wool is denser and stiffer than fiberglass and is less likely to slump and create noise transfer zones. It doesn’t make you itchy with bits of glass and has no airborne particles that can irritate the eyes and breathing passages. It also has higher R values, preventing airflow, which also prevents sound transfer.
Use in exterior walls or ceilings and floors to reduce sound and echo. I used it on interior partition walls to reduce sound transfer between rooms, and it also helps reduce feedback within the rooms.
Roxul Rockboard 60 and 80
Roxul Rockboard is rigid panels made for use in ceilings and floors, as well as walls. It not only provides a thermal barrier, but also improves sound absorption, and impact vibration and noise.
Roxul is made from mineral wool spun from molten basaltic and igneous rock. They can be easily cut and even shaped. The 60 has a density of 6 lb/f³, and the 80 has 8 lb/ft³.
Rockboard 60 and 80 have similar acoustic properties. A 2-inch thick panel of Rockboard 60 has an NRC of 0.95 while 80 has an NRC of 1.0.
Both can improve a partition wall to between STC 45 and 52. Rockboard 80 is better with low range frequencies, and the 60 board is better at the mid and upper frequencies. Additionally, the panels are fire, water, moisture and rot resistant.
Rockboard can be used on exterior walls and covered with cladding, inside wall cavities, and even in ceilings. It can also be framed and covered in acoustic fabric for use as sound absorbing panels in media or music rooms, or anywhere you want to reduce sound transfer and feedback.
- Roxul Rockboard 60 is made of mineral wool and available in 2” thick 2’x4’ boards. They easily fit into wall framing cavities or can be framed and covered with cloth to make movable noise reduction panels.It’s a rigid panel that can be cut and shaped for any use.It works well to trap mid and upper range frequencies, and is effective with low range too. It can even be used to make acoustic base traps.The heavier density of the 60 helps it reduce echo or slap back noise within a room, and because it’s insulation, it has an R-value that helps maintain room temperature better.
- Roxul Rockboard 80 mineral wool insulation panels are 2’x4’ sheets that are 2”thick. They have a density of 8 lb/ft³ and an NRC of 0.9, so are great for soundproofing.Mid to upper range frequency is excellent NRC 0.9 or better, and a respectable low range coefficient, make the Roxul acoustic panels a top choice to absorb or reduce sound transfer.They can be used inside walls, ceilings or floors, or as independent framed panels hung where needed to deal with echo and feedback. Additionally, the mineral has a great fire rating, is moisture and mold resistant, and improves the heating or cooling of a room.
- Roxul Acoustical Fire Batts (AFB) are made of mineral wool, so are also water, moisture and rot resistant. The 2” thick, 2’x4’ batts are a lighter 2.5 lb/ft³ which doesn’t prevent them from being a heavyweight in noise transfer reduction.The AFB has mid and high range frequency ratings of NRC 1.05 to 1.09 and can be used inside walls, ceilings, and floors or as framed panels. It is more flexible (less rigid) than the board products, so can be used to wrap as well.
Fiberglass insulation is spun from melted plastic with tiny shards of glass embedded into it. It is a loose material which traps air, which in turn can trap or absorb sound waves.
It doesn’t have the density though to block them. Fiberglass also has thermal properties that help to keep a room warm or cool, depending on the season, so it works well for home construction.
Using standard 3-1/2” thick fiberglass batts in wall cavities can improve the STC from a rating of 35 to 39. The sound that travels through drywall is further reduced before it transfers into the next room.
However, as the STC rating show, the improvement is marginal. However, they do perform well at reducing echo and feedback within a room.
Fiberglass insulation (the fluffy stuff) is not a rigid material and can experience slump and compression over time. It also has to be compressed to cut, reducing both its R-value and sound absorbing ability unless fluff-up again. 2-1/2” thick R8 has an NRC rating of 0.85, 3-1/2” thick R11 is NRC 0.95, and 6-1/4” thick R19 is rated NRC 1.05.
As you see, thicker the product, the higher the R-value, and the better its ability to absorb sound. However, any compression of the fiberglass reduces both the R-value and the absorption ability.
Semi-rigid and rigid 2” thick 2’x 4’ fiberglass panels range from an NRC rating of 0.50 to 1.00 depending on the product; the higher the cubic foot density, the higher the rating. Like the fluffy insulation though, it too is susceptible to moisture and mold.I suggest using the fiberglass batts to insulate exterior walls, interior walls, and ceilings to reduce noise transfer, echo, and feedback within all rooms. The semi-rigid is a good option for irregularly shaped cavities, floors, and ceilings, or between ducts and pipes to reduce sound and impact transfer.
The rigid panels can be used in walls, ceilings, and floors, on exterior walls to add both a thermal and sound barrier, and as moveable panels to absorb sound and feedback. Great for all room applications, but especially rooms you want to reduce feedback in and sound transfer from.
Products of Interest:
- Owens-Corning has a 23”x39’ roll of pink unfaced insulation that fits between trusses, joists or studs, adds 6-1/4” thick of insulation with an R-19 value, and an NRC rating of 1.05. It is moisture and mold susceptible though. It will improve the sound absorption between floors and walls if it isn’t compressed.
- Owens-Corning 703 Acoustic Insulation 2” thick rigid 2’x4’ panels are lightweight and can be used in ceilings, walls or framed and hung where needed to reduce feedback and echo. The panels should be covered with an acoustic fabric to prevent fibers from becoming airborne.As with all insulation, the density impacts its noise reduction ability, as does its composition. Within the 2” thick 3 lb/ft³ dense 703 products, the NRC ranges from 0.75 to 1.00, so check the product to ensure you’re getting what you want.
- Owens-Corning 2” thick Soundproofing Insulation has a density of 10 lb/ft³ and claims it will add an STC of 18 to your uninsulated wall with an STC of 35, to bring it to an STC of 53. It has an NRC rating of 1.0, performing better at the upper test frequency than the lower end, so low-frequency noise is still an issue.
Sound Deadening With Blown Cellulose Insulation
Cellulose insulation is composed of 75-85% recycled paper fiber with the remainder being made up of fire retardant mater. It has an STC rating of 44 and an NRC of 0.80 and can be added to walls, floors, and ceilings during or after construction. It reduces the vibration resonance within a wall or ceiling, absorbing, damping, and deadening sound.
Available in loose fill, wet, or dense pack, cellulose not only provides a sound reduction, but it is also an excellent thermal insulator. Loose filled is blown into wall and ceiling/floor cavities under a lighter pressure, while the dense pack is blown in under higher pressure creating a solid 3.5 lb/ft³ of density.
Cellulose traps air which in turn traps sound waves and helps deaden sound between walls and floor levels. Wet cellulose can be applied to walls, ceilings or around irregular surfaces to depths that reduce sound transfer and improve R-values.If you’re looking for a way to improve sound quality and reduce noise transfer in interior walls, go with cellulose. I’d even recommend it for use in exterior walls and ceilings too.
I’ve used it for all of those and am amazed at the differences it made not only to improve the thermal barrier but sound also. The echo, reverberation, and feedback within rooms and halls almost disappeared, and sound transfer between rooms and floor levels was lessened too.
Use it in multimedia and music rooms to improve sound quality and reduce sound transfer.
- U.S. Greenfiller LLC Fiber Insulation is loose fill cellulose for blowing into walls or attics. It has an R-value of R-19 at 4” thickness. The thicker, the better for both thermal and noise insulation. It has an STC rating between 44 and 68 depending on thickness and density.
- Acoustimac Acoustic Insulation ECO CELLULOSE comes in soft, yet rigid, 48″x24″x2″ sheets. With a density of 4 lb/ft³, it can be used in walls, ceilings or floors. It can also be framed and used as movable panels to maximize their sound benefits. They will deaden reverberation and echo, improving sound quality in a room, while reducing noise transfer through walls.
Soundproofing with Spray Foam
Spray foam is polyurethane foam that provides not only thermal insulation but also acoustic insulation. It is a dense material that blocks or resists sound waves or vibration.
Spray foam helps to muffle or reduce sounds from entering a room or building and do the same to sounds transferring out of a room or building. Spray foam can be used for new or existing construction applications, and are fire retardant.
Spray foams are better at blocking noise from moving between floors and rooms, than absorbing noise. The foam is available in open and closed cell formats.
The open cell is less dense than the closed, soft, sound damping, has a lower R-value, and is rated for indoor use.
The closed cell acts as a moisture barrier when cured, is hard, can be used indoors, and can act as a structural reinforcer. The closed cell also dampens sound, but since it cures hard, it can separate from wood frames causing sound transfer channels. Three inches of spray foam has an NRC of 0.70. The STC rating for open cell foam is 39, and the closed cell has an STC of 37.I’d recommend the spray in ceilings and inside wall cavities to reduce sound transfer and dampen sound. Combine it with mineral wool or fiberglass, and you’ll have an excellent sound absorbing barrier.
Use it in recreation areas to deaden noise and impact sounds, and multimedia rooms reduce sound transfer. Remember though; insulation is only part of the solution.
Products of Interest:
- Foam It Green 602 closed cell spray foam kit will cover 602 sqft to 1-inch thick under perfect conditions. The kit produces an excellent thermal barrier, plus an air, moisture, and sound barrier. The sound blocking ability can be compromised over time. It is also less temperature sensitive than the open cell spray.
- Foam It Green 1202 Class 1 open cell spray foam kit is a DIY product that allows you to add acoustic value to any wall, ceiling or floor space. In perfect conditions, it can cover up to 1202 sqft at 1-inch thick. It will make an air barrier, and thus a noise barrier to reduce noise coming in or going out of your room. A drawback is that the product is temperature sensitive which affects expansion and coverage.
Using Styrofoam Insulation for Soundproofing
Styrofoam is a brand name for a polystyrene foam board. Polystyrene boards, whether pink, blue, white, or another color, are usually used in construction, but it has other applications as well. Acoustically it can reduce and muffle, or help block noise from entering or leaving a room.
Polystyrene comes in extruded and expanded formats. The extruded are often pink or blue foam boards that are stronger and denser; the colors represent manufacturers. Extruded is the white, more brittle, foam that makes round snow when broken or cut.
Polyisocyanurate (ISO) is another extruded foam board. It has higher R-values per inch of thickness, which also makes it a better noise blocker.
It is also more expensive than the other products. The boards are also available to fit into drop ceiling grids too, to further reduce sound transfer between rooms and floors.
Polystyrene or Styrofoam products are used for camp coolers and coffee cups, so they have thermal properties. Those thermal properties translate into sound reducing or resisting properties.
Sound is a vibration; the foam boards reduce the vibration transfer, which helps reduce noise transfer. However, its real use is as a sound blocker.
Extruded boards are closed cell foam, so it’s safe to say it has an STC of 37. Expanded foam boards have a more open cell construction with air spaces which absorb sound waves, like another open cell rigid foam, its STC may be slightly greater at STC 39.
When used in standard partition wall construction, it can increase the wall STC rating to between 51 and 55. It also has an Impact Isolation Class (IIC) rating of 70.
Styrofoam or polystyrene boards work well for exterior wall applications or can be combined with mineral wool or fiberglass panels in interior wall cavities as an impressive sound absorbing, deadening, and sound decoupling barrier. The boards can also be wrapped and hung for use within music or multi-media rooms to dampen sound.
Products of Interest:
- Styrofoam Foam Sheets are lightweight and can be covered with acoustic fabric and used as sound blocking panels to reduce sound transfer. The material can also be used to fashion bass traps to absorb or deflect low-frequency sound.
So, What Type Of Insulation Is Best For Soundproofing? Comparison
What is the best insulation for soundproofing? It depends on a multitude of factors: pre or post construction, construction techniques, inside the wall, ceiling or floor cavities, hanging on a wall, whole house or select spaces, type of noise, and BUDGET. If soundproofing were only dependant on insulation, for the money, I’d pick cellulose.
Another variable is the literature you read. We’re talking multi-billion dollar industries competing for a bigger market share, so they’re going to make themselves look better and tell you how bad others are.
If you can find an independent lab that has done all the NRC, STC, SAA, and IIC tests on the products you’re looking at, AWESOME!
Most partition walls and multi-story floor-ceiling cavities are not insulated. Adding insulation after construction, short of renovating, isn’t practical. However, there are two products available that will work for post-market wall and ceiling insulating, blown-in cellulose and spray foam.
The soundproofing comparisons here are based on information available, and the most credible sources found. No comparison is perfect since each brand has numerous products in every category.
Mineral Wool vs Fiberglass Insulation Batts
- Mineral wool batts (3.5” thick) have an STC of 45 and an NRC of 1.05, are more rigid and have a higher R-value/inch of thickness. It is water, mold, and mildew resistant too.
- Fiberglass (3.5” thick) batts have an STC of 39 and an NRC of 0.85, they are not rigid and tend to compress and slump, reducing their noise absorption abilities.
Mineral Wool Panels vs Fiberglass Panels
- Mineral wool (2” thick) panels have an STC between 45 and 52, and an NRC range from 0.95 to 1.09. They work well in walls and as panels to absorb sound, reverberation, and echo.
- Fiberglass (2” thick) panels have an STC of 44 and an NRC of 0.50 to 0.95 depending on the product. They too can be used as wall panels to reduce sound, echo, and reverberation.
Cellulose vs Fiberglass Batts and Panels
- Loose fill cellulose has an STC of 44 and an NRC of 0.8. It can be sprayed in during or after construction and is mold, insect and rodent resistant. Additionally, it is 75-85% recycled material and the least expensive option, especially for whole house applications.
- Dense pack cellulose has an STC of 44 to 68 and an NRC of 0.9. A pre or post construction product, it absorbs sound, feedback, and echo.
- Fiberglass batts have a lower STC of 39 but a greater NRC of 0.95. Their tendency to compress and slump reduces their noise absorption abilities. They are also a pre-construction or renovation option only.
- Fiberglass panels have an STC of 42 and an NRC ranging from 0.50 to 0.95, depending on the product specs. The panels are rigid and can be used on walls to dampen or absorb sound and echo.
Cellulose vs Roxul Rockwool
- Cellulose, depending on its density, has an STC range from 44 to 68 and an NRC between 0.8 and 0.9. Made of 75 to 85% recycled paper, it can be used in pre and post construction applications. It’s a good sound absorber, and reduces feedback, and echo.
- Roxul Rockwool batts are 3.5” thick and have an STC rating of 45 and an NRC rating of 1.05. It is more rigid than other batts but is a pre-construction product. Rockwool has good mid to upper sound absorption ratings, and even the low end is respectable. It also helps reduce reverberation and feedback sounds.
Cellulose vs. Spray Foam
- Cellulose has an STC range from 44 to 68 and an NRC between 0.8 and 0.9 depending on its density. It is 75 to 85% recycled material and can be used in pre and post construction applications. It’s a good sound absorber and reduces echo and feedback.
- Spray foam has an STC of 39 for open cell and 37 for closed cell, and an NRC of 0.70. Like cellulose, it can be applied pre and post-construction. It is less a sound absorber, and more a sound blocker. It is also significantly more expensive than cellulose.
Rigid Foam vs Roxul Rockboard Panels
- Rigid foam, depending on the product, has an STC between 37 and 55, an NRC of 0.70, and an IIC of 70. It isn’t a good sound absorber as much as a reflector or deflector. Sound can still go through it, but some sound doesn’t. It works best at preventing noise from entering or leaving a room.
- Roxul Rockboard panels are 2” thick and have an STC rating between 45 and 52, and an NRC between 0.95 and 1.09. They work well in ceilings and walls, and as moveable panels to absorb sound, reverberation, and echo.
Tips for Using Insulation to Soundproof a New Building
The main purpose of building insulation materials is to reduce air flow through the walls. It traps air to keep the heat or cold out or in, depending on the season. The greater R-value usually means it’s better at preventing air from moving through the wall and thus sounds too.
That doesn’t mean it stops all sounds. Noise is a wavelength which is also a vibration. Insulation is one factor in the sound reduction game.
New techniques, new materials, more time, means greater cost of building. The best way is to determine where you will need or want improved soundproofing.
I’m talking about exterior and interior walls. Residential areas can be very loud, and if someone needs to sleep when others aren’t, that can be a big problem.
Reducing the sound entering the house is the first step. Soundproofing exterior walls with rigid exterior insulation under the cladding is a good start.
Break the sound wave vibration path by staggering the studs.
Use mass loaded vinyl (MLV) to create a sound barrier will also reduce sounds. Insulate the wall cavities with a high R-value insulation; the higher the R-value, the more sound absorbed or blocked.
Don’t forget the attic and gable ends either. The more insulation the better for heating and cooling your home, plus reducing noise transfer.
Use sound sealing foams and gaskets around doors, windows, and any other openings through the exterior walls. HVAC, dryer vents, ductwork, and bathroom exhausts are the quickest way to destroy your soundproofing efforts.
They create a resonating tunnel for sound vibrations! There are duct pipes available that are designed to minimize noise transfer too.
Where floors, walls and ceilings meet is another area sound transfer will occur from outside in, or between rooms. There are building techniques that will minimize the transfer, discuss them with your builder; viscoelastic damping is one possibility.
Interior wall surfaces can have thicker drywall, double layers of drywall, or damped drywall. Damped drywall is more dense and better at soundproofing than regular drywall.
Metal studs transfer less noise vibration than wood and make a great sound barrier when insulated properly. Thicker walls with offset studs will break the structural sound transfer between rooms. Using resilient channels will also break the transfer if installed correctly. Even the placement and type of screws or nails can improve the soundproofing performance of a wall.
Remember, pipes and electrical boxes can transfer noise too. Offset electrical boxes in different wall cavities. They will transfer noise if in the same cavity and especially if back to back. Use acoustic caulking to seal all gaps or openings to prevent sound from penetrating the barrier.
The floor is another area sound reduction and impact isolation can occur. Using felt underlayment, insulating between joists, and installing a floating floor are some of the ways sound can be reduced within a house.
Leaving a mechanical break between the floating floor and walls is another method that will stop sound and impact transfer. Using a thick bead of caulking or sill plate membrane under interior walls can also reduce sound and impact transfer.
New products and techniques are always being developed and marketed, so if you’re building or renovating, keep up to date.
Other Ways to Soundproof Your Home
There are other ways to improve the soundproofing of your home. Acoustic paint properly applied can improve the STC of a room by 3-7points.
Soundproof caulking used between drywall and studs and around outlets can further reduce sound transfer. Sound blocking windows, doors, and weather stripping are also available.
- Roberts 70-193 Super Flooring Underlayment is a roll of 3mm thick felt for use under wood floors on concrete or wood subfloors. It is 60-inches wide and 72-feet long and covers 360 sqft. With an STC rating of 66 and an IIC of 67, it reduces sound transmission between floors and echo within rooms.
- ATS Acoustic Panel are 2’x4’ and 2-inches thick. They can be hung in different areas to help control echo, feedback, slap and reverberation within a room. With an NRC of 1.0, they work well in music and entertainment rooms to absorb sound within the room. They can be used on walls and ceilings too.
- You can make your own using rigid mineral wool, fiberglass or bonded acoustic cotton panels. Frame them in a 2’x4’ frame and cover with acoustic rated fabric, and enjoy!
Soundproof Windows and Doors
- Soundproof Weather Stripping Door Stopper kit has 16-feet of self-adhesive window strip and 30-inches of door sweep. Helps keep weather, sound, smells, and insects out of your house! Works for patio doors too!
- Changlian Self-adhesive Door Draft Blocker is a rubber weather stripping. It attaches to the bottom of exterior and interior doors and will help reduce sound, wind, bugs and odors.