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Noise Control in Multi-Family Residential Buildings

Noise control in residential buildings is one of the most common inquiries we get in our website’s “What’s Your Problem?” feature.

We are overwhelmed with questions about noise and acoustical problems . Not the least of these inquiries have been from owners or renters in apartment complexes, townhouses, apartments, and offices. The problems range from noise transmission by noisy upstairs neighbors , through adjacent party walls between neighboring units or through windows. The noise control problems associated with floors and ceilings range from airborne noise transmission from voices, TVs and music to footfall impact noise and from plumbing noise. The noise pollution caused by that noisy neighbor can be reduced using common methods of residential soundproofing. Sad to say, for newer residential units many of the problems could have been prevented in the first place if good acoustic design principles had been followed during the design and construction process. After the fact, when the noise problems are discovered, solutions can be very difficult and expensive to resolve and in most cases, there is no easy solution. Jump to Key Sections:

Design and Building Codes

For newer or remodeled multi-family dwelling units, the various Building Codes throughout the United States require a measure of sound insulation between floors of multi-family dwellings. The Building Codes specify a minimum architectural design standard of privacy of 50 STC (Sound Transmission Class) and a 50 IIC (Impact Isolation Class). The Building Codes also state that validation of the minimum noise criteria can be field measured and the field measurements shall not be less than a 45 FSTC or a 45 FIIC. While some community building inspection departments require field-testing to be conducted before a certificate of occupancy is issued, many, if not most, do not. They rely instead on the architect’s specification and acoustic design recommendation and the expectation that their specified designs will result in the minimum sound isolation construction between adjacent units. Unfortunately, what is specified by architectural sound design and what is subsequently built do not always coincide if proper attention and inspection oversight are not implemented. If your residential dwelling is relatively new or if you are contemplating the purchase of a unit, do not be afraid to question the contractor and the real estate agents about the sound isolation characteristics of the unit. Just because they say that the units have been built to code requirements does not mean that they meet the minimum code requirements. If they do not, you may have a case to demand corrective action at the expense of others. Do not be left holding the bag; moreover, a certificate of occupancy by local building inspection departments implies that the structure has been built to minimum code standards.

How the Sound Transmits in Residential Buildings

Contrary to what many think, sound waves don’t merely pass through material; instead, sound energy excites and vibrates any material it comes in contact with, making it a transmitter of the sound. In order to control acoustic efficiency, thinner and lighter materials with varying acoustical characteristics are often employed. Insulation in the cavity converts some of the energy into heat, while resilient channels minimize the direct connection of the gypsum board.  Each material and the relationship between them produces incremental improvement in sound isolation, thereby lessening the transmission of sound throughout the entire system.  For example, a 2” x 4” wooden stud wall system with 5/8” gypsum board on either side will generate an STC rating of 35. With the addition of insulation to the wall cavity, this rating can rise to 40, with a resilient channel increasing it further to 45. A second layer of 5/8” gypsum board can add a further 5-8 points to the STC rating, bringing it up to between 50-53.  Each wall assembly should be inspected meticulously to ensure that all materials are used and installed correctly, and that variables such as the stud spacing, the thickness and density of insulation, the spacing of resilient channels and the direction of the gypsum board have all been taken into account in order to reach the desired sound performance of the assembled system.

How can I reduce noise from Neighbors?

Purchasing a condo or townhouse may be one of the most significant expenditures you will undertake; therefore you have every reason to expect answers with respect to your privacy needs and freedom from intrusive noise from your neighbors. If you have a noise problem that is not resolved and you go to sell your unit, you may be compelled to reveal the deficiency to a prospective buyer which can have an impact on the selling price.

Limit Noise on a Shared Wall?

Very few, if any inspection agencies actually check the quality of construction from a sound isolation perspective and too few building contractors are really conversant with good acoustic considerations design.  As a typical example of what can go wrong, take a party wall between two alongside units. The wall may have been designed for a 60 STC value but when installing drywall installs the gypsum board, many of them will jack the gypsum board up tight to the ceiling to ensure a nice clean and tight joint at the ceiling line.  While there is nothing wrong with this practice, far too often it will leave a void at the floor line, which will eventually be hidden by the baseboard. Any voids at the floor line must be caulked.  The wall selected from the gypsum drywall design guide to achieving a 60 STC was selected from the gypsum manufacturer’s design guide based on actual acoustical laboratory tests. Close inspection of the acoustical test data is bound to reveal that in the test chamber the wall was caulked into the test opening to prevent any sound leakage.  If this is not repeated in the field during actual construction, sound leakage can and far too often, will occur. The lack of a few pennies worth of caulking compound can reduce the sound performance of a 60 STC rated wall to less than the minimum of FSTC 45 required by the building code.  There are many causes for sound leaks, such as uneven floors, wooden floor plates that are not perfectly straight; no matter what the cause, they can all be sealed to insure an airtight barrier thereby maximizing the acoustical performance of the wall.

Arranging Rooms in Buildings for Noise Control

First things first – we need to divide rooms into two groups: less sensitive and more sensitive to noise. Less sensitive rooms include the kitchen, bathroom, and the likes. More sensitive rooms are rooms like bedrooms and living rooms. The rooms must be arranged in such a way that the more sensitive rooms are shielded from the noise and that the less sensitive rooms are closer to the noise source, guarding the more sensitive rooms.

Arranging Balconies for Noise Control

Balconies or terraces provide access to the outside environment, as well as fresh air and daylight. They are one of the most desirable parts of an apartment complex, but their improper arrangement can nullify all that through the undesirable noise. You have to have in mind where the building is oriented. Exposure to the high traffic area would promote the noise entering the building – a common problem for high-density cities. In such cases, measures that reduce the impact of noise must be put in place. Check out our Acoustics 101 section and soundproofing tips for more resources and information on acoustics in architecture.

Soundproofing Walls

Fortunately, airborne sound leakage can be easier to detect; as one can do so by getting close to the wall, albeit on all fours, and listening for the sound coming through the wall. You may need the cooperation of your neighbor by playing a radio next door so that you have a sound signal to listen for.

How do I stop noise coming through walls?

The sound will become louder as you get closer to the leak. If the sound appears to be coming from the base area, a solution may be to remove the base by hand to see to see if the gypsum board and the floor were caulked. If not, caulk it. If the floor is carpeted, the baseboard will normally be positioned just above the carpet, in which case it is possible to insert a probe such as a long flexible knife blade. If the blade goes in more than about 3/8″ or if it hits something hard or does not come out with any caulking residue on it, there is a good chance the wall was not caulked as required by the gypsum board manufacturers literature. Equally important, party walls that extend to the roof or floor structure above the drywall ceiling in a dwelling unit should likewise be fully sealed. Just because it cannot be seen following construction and subsequent occupancy is no reason to believe that an unsealed wall is not going to create noise problems at a later date.

Soundproofing Windows

Sound level intrusion through windows can be a source of annoyance, which can be due to a variety of factors. If the windows are operable types, the first thing to check is to see if the windows close properly and any weatherstripping is in good shape. If the window can leak air it can also leak sound. If the window closes to form a tight seal and the weather-stripping seems adequate the next thing to check is the window frame.

How can I soundproof my windows?

Windows are frequently installed into the wall opening with wooden shims to ensure the unit is plumb and level. Interior spaces between the frame and the wall should be insulated and sealed before the window casings are installed. If this was not done correctly you can probably detect the sound leakage by placing your ear close to the frame and listening.  It is a case of letting your ears do the walking and listening. If you detect noticeable differences in the sound you may have found the problem; the solution will be to remove the casing and insulate and caulk any leaks. If all else fails, the thickness of the glass may be the problem. In that case, it may be necessary to install another layer of glass on the inside in a similar fashion to the storm windows on the outside. Just make sure that the additional pane of glass is well sealed into the opening.

Floor/Ceiling Assemblies for Noise Reduction

Floor and ceiling assemblies can be the pathway for two types of sound transmission, the first is the airborne transmission of sound and the second is the passage of impact sounds such as footfalls on the floor above.  Assuming that the floor-ceiling assembly has been designed and constructed to provide adequate airborne isolation, impact noise can still be a problem. If the finished floor surface has been designed to accommodate carpeting, the carpeting and underpad will normally provide a good degree of impact sound isolation.  On the other hand, when the finished floor is floor tile, hardwood flooring, or ceramic tile. Achieving good impact sound isolation requires much more attention. Frequently, the solution is to install an impact sound-absorbing flooring underlayment to separate the finished floor from the subfloor structure.

Can you soundproof an existing floor?

In isolating the finished floor from the sub-flooring it is necessary to make sure that any potential leaks are adequately sealed. Many times a floor is constructed with a layer of concrete or gypsum topping over the subfloor. When this is done any sound-isolating underlayment should be sealed so that the topping will not leak between the underlayment material joints. This can short-circuit the expected sound-isolating benefits of the underlayment. Selection of floor joists is an important consideration also; solid 2″×10″ joists provide a very good base for good sound isolation. Open web wooden truss joists seem to be less effective at very low frequencies to a greater degree than solid wooden joists so special attention should be paid to the use of these types of joists. Rubber underlayment is an effective way to reduce noise in buildings, especially in multi-story buildings where noise from the upper floors can travel down to the lower floors. Here are some steps to reduce noise using rubber underlayment. The first step is to remove the existing flooring to install the rubber underlayment. The underlayment will be placed between the subfloor and the new flooring. After removing the old flooring, clean the subfloor thoroughly to ensure that the rubber underlayment will adhere properly. Roll out the underlayment and cut it to fit the room. Make sure that the seams are tightly joined together. Once it is in place, install the new flooring on top of it. This will help to absorb sound and reduce noise transmission. After installing the new flooring, use acoustic sealant to seal the edges and gaps between the flooring and the walls. This will prevent noise from leaking through the edges.

How do you soundproof a ceiling between floors?

One of the most common sound isolation elements in floor-ceiling construction is the use of a metal resilient channel isolator that is attached to the underside of the floor joists before the gypsum board ceiling is installed.  The gypsum board panel is applied to the resilient channel isolator in a manner that ensures that the screws used to apply the gypsum board do not extend into the joists to which the resilient channels is applied. Special care and attention should be taken with the selection of a resilient channel as they are not all the same and do not all provide the same degree of isolation.  Pay attention to the installation and spacing of the resilient channel. It is wise to consult the manufacturer’s acoustical test report and to specify and ensure the channel is installed in the same manner in which it was installed in the acoustical test lab.  If the resilient channel has not been tested by an independent test lab and is simply another look-alike channel, do not use it, select another with a known performance rating. Above all, be aware that not all resilient channels perform the same. Do not skimp on floor-ceiling construction, as it may be costly to improve the sound isolation performance after the fact. It is highly cost-effective to create sound insulation between the floor joists and apply two layers of gypsum board to the underside of the resilient channel as opposed to a single layer.

I Have a Noise Problem, What Can I Do?

If there is any consolation, perhaps the most frequently encountered problem may be the easiest to fix, furthermore it can also be one of the easiest problems to detect. As previously indicated, the lack of effective noise caulking at the floor line behind the baseboard is one of the most common causes of sound transmission from one space to another.  It can be detected quite easily just by listening. It may necessitate having to get on your knees and placing your ear close to the baseboard. If the sounds you hear from the adjacent space are more noticeable than from other parts of the wall surface, you may have found the problem yourself at no cost.  The solution is then to remove the baseboard and caulk any voids between the gypsum board and the floor. You would be surprised how often this turns out to be the problem. If the problem is not an air/sound leak then the problem becomes a little more complicated. Simply adding another layer of gypsum board may not necessarily be an effective solution as an additional layer of gypsum board may only improve the performance by 2-3 points, which is barely detectable by the human ear.  Adding a resilient channel to the existing wall or ceiling and an additional layer of gypsum board will not work, as the resilient channel requires larger airspace behind it to register any significant improvement. Also adding a layer of lead or loaded barrier will only produce a minimal improvement that is not a cost-effective solution. Unfortunately, a more effective solution will be to remove one layer of gypsum board to ascertain if the wall has been insulated if it contains a properly installed resilient channel. At the same time, you need to look to see if there are any holes in the bottom plate of the wall where electrical or plumbing services have been installed and ensure that they have been adequately sealed with a caulking compound.

Frequently Asked Questions:

What Materials Can Block Sound?

When it comes to choosing the right soundproofing material, there are various inexpensive solutions to secure your peace and quiet. These are the most effective and cost-effective as well. Some of the best solutions for effective noise control in residential and Mass loaded vinyl, green glue, soundproof curtains, acoustic foam, etc. If the building structure doesn’t allow much experimenting there are some hacks that could help – soundproofing floors and ceilings and a bit of furniture rearranging can have a positive impact on blocking the sound.

Does Soundproofing a Room Work Both Ways?

Yes, most of the soundproofing options will work both ways, but differently. Decoupling will isolate outdoor sounds from indoor sound while adding mass to walls will help with the better reflection of sound waves. Acoustic panels are great for controlling the echo in the room and appropriate sound management could reduce sound pollution. The best thing is that insulation and soundproofing can go hand in hand – if you decide to add Green glue to the mix. It will help you save on the utility bill as well! The secret lies in combining the two soundproofing options to achieve the best effect possible. That could be useful for both you and your neighbors as well.