You’ve been very happy in your apartment, but new neighbors have recently moved in and ruined your peace and quiet.
They talk loudly, their kids shout and scream, they play their music until the early hours, and you have to find solutions on how to reduce noise through walls before you lose your mind.
What options do you have? You can start here with a few sound-reducing ideas:
- Find out what the STC rating is on your walls, so you know what your starting point is
- Insulate your walls with sound-dampening tiles, MLV, green glue, or other materials
- Install solid core doors that will absorb the sound rather than hollow doors that let the noise right in
We’ll take you through all these options and more, and you’ll forget all about those sleepless nights.
Points to Keep in Mind
Before you go out and buy all sorts of soundproofing material that friends have recommended, you need to find out a few basic facts first.
How is sound transmitted?
Sound travels in waves, created by vibrations of air molecules that rebound off each other.
You hear this as noise when it reaches your eardrum. Your brain identifies the volume and pitch of the sound, and you are able to recognize a child crying, an airplane taking off, and heavy rock music.
The air carries sound waves, so wherever there is a place for air to penetrate, the sound will be carried along with it.
Hertz is the frequency of the number of vibrations per second. Humans can hear sound between 20Hz – 20MHz.
Pitch is determined by the frequency of the sound wave vibrations. A high-frequency results in a higher pitch and vice versa.
What does this have to do with your walls?
Sound waves are very good at penetrating most materials, so the thicker your walls, the less noise can penetrate.
This does not mean you must have concrete walls in your apartment — there are many ways you can add soundproofing to regular drywall partitions.
Type of Wall and STC Rating
STC (Sound Transmission Class) is a rating given to walls, windows, doors, and other construction components by the American Society for Testing and Materials (ASTM).
Their standards are used by anyone related to the building industry, including:
- Producers of acoustic products
But what is STC?
It means the difference between two measurements of sound on either side of a barrier, such as a wall.
The first measurement is taken where sound e.g., music is generated. The second measurement is taken on the other side of the wall (which may be an adjoining apartment).
The difference in these dB readings is the STC.
STC ratings range from 125Hz – 4000Hz, so deep bass sounds below the minimum range will not be measured.
An STC rating of 50 is considered acceptable in buildings with drywall partitions: the higher the STC rating, the less sound penetrates.
Why does an STC Rating Matter?
You will need to know the STC ratings of your walls to be able to take effective measures on how to reduce sound between rooms.
The lower the rating, the more sound penetrates, as the STC ratings illustrated here show:
20-25 low speech is audible
30-35 loud speech can be heard and understood quite well
50-60 loud sounds can hardly be heard
So if you don’t want to continually be disturbed by whatever your neighbors are doing, you need to know how to muffle sound in a room by increasing the STC ratings of your walls.
Building Codes for Sound Reduction
STC ratings are pinpointed at determining values within a range of 16 frequencies, e.g.:
50Hz = 42dB
125Hz = 45dB
1250HZ = 60dB
The International Building Code (IBC) was updated in 2018 and now includes a stipulation for Group-R occupancies, which includes residential buildings i.e., :
These codes are set by individual jurisdictions according to their own requirements but are guided by the IBC.
What Type of Noise Do You Want to Reduce?
To get any decent sleep, you need to know how to reduce noise through walls.
If you live on a busy street, you will want to have constant traffic noise reduced.
Other intrusive noise can be caused by a number of factors, such as:
If you are trying to concentrate on finishing your thesis, you don’t want to hear a pneumatic drill or a bulldozer working for hours at a time.
You may have a demanding job and really need to get restful sleep. The music from the nightclub on the next block keeps you awake, as do the patrons shouting and celebrating as they leave the premises.
If you have ever heard cats fighting, you will know how disruptive that can be to your sleep. The high-pitched yowling and screaming are sure to wake you up with a jolt.
Your neighbors may have a pet parrot, which can imitate sounds from a ringing phone to a fire engine siren.
Any of these is sure to make you desperate to reduce the noise coming through your walls.
How Do You Reduce Noise in a New Wall?
You’ve decided to put up a new partition wall between your kitchen and living room to create a quiet study space.
What should you consider incorporating in your new wall to reduce noise?
Noise Reducing Drywall
You could install a double layer of normal drywall, but there are commercial products available that claim to reduce sound transmission through walls.
All these products comprise multi-layers of gypsum, ceramic and viscoelastic, which comprises a mix of viscous liquid and solid elastic.
The multiple layers mean the sound molecules have less room to vibrate, reducing their capacity for noise.
The first principle to remember when trying to soundproof a room is that mass matters.
The thicker a wall, the fewer chance soundwaves have to escape.
Wall drywall is ½” thick, so double layering will create a sound barrier of 1” thick.
Layering the second sheet 900 to the underlying sheet will help, as the studs and seams will not line up and, therefore, not create a sound channel.
Insulate Interior Walls
Insulating interior walls as they are installed is an efficient way to stop sound before it starts.
You can use a variety of products in the cavity between the drywall sheets, such as:
- Acoustic eggshell foam
- Cellulose (paper) insulation
- Expanding foam
- Fiberglass batting
- Foam panels
Ensure that any product you use is fire retardant and will not emit dangerous fumes.
Sound Dampening Tiles or Panels
There is a difference between sound dampening and sound blocking.
Sound blocking does what it says — it prevents sound waves from moving through solid objects.
Sound dampening reduces echoes, reverberations, and general ambient noise.
The NRC (Noise Reduction Coefficient) scale measures sound between 0-1. A zero rating means that no sound is absorbed, and a rating of one means that all sound is absorbed.
Acoustic panels and acoustic foam tiles are recommended for sound dampening.
You can fit as many panels together as you require, and they are generally lightweight and easy to install.
Sound Isolation Clips
Sound isolation clips are an effective solution to reducing noise through walls.
They consist of metal clips that are screwed into the joist. A neoprene mount on the clip separates the clip from the stud and helps to absorb sound.
These are a more expensive option than some other methods, but they will absorb low-frequency vibrations such as bass music.
How Can You Reduce Noise Through Existing Walls?
Any cursory Google search will give you hundreds of answers on how to reduce sound in a room.
Here is a concise list of suggested solutions on how to reduce noise through existing walls:
You can install a double layer of the drywall as any additional mass is helpful for stopping soundwaves traveling into a room.
You can attach another layer of drywall to new or existing walls
Due to fire code regulations, the drywall is hung in horizontal sheets in residential properties but vertically in commercial properties.
Mass Loaded Vinyl
Mass Loaded Vinyl (MLV) is one of the best options for soundproofing a room.
It’s lightweight, easy to apply, non-toxic, and inexpensive.
It is designed to hang in loose sheets, which deters sound waves from bouncing off it.
MLV is attached to the joists with screws or nails, and the seams are covered with acoustic caulking and seam tape.
MLV is installed between two sheets of drywall, thereby absorbing sound energy that penetrates the hard wall surface.
Who would have thought that a coat of paint could be a sound barrier?
It’s true — but only up to a point.
The paint is much thicker than regular products and consists of thermals: cells that are vacuum sealed and contain flexible pigment, which moves with the sound waves.
Soundproofing paint is only minimally effective at reducing sound and will not absorb anything other than faint background noise.
Plugging Sound Leaks
Sound has a way of penetrating every crevice that is not completely sealed.
For example, you may have installed foam panels on your door, but if the door is not a tight fit in the frame, you’ve wasted your time.
Affixing a rubber strip underneath the door is a great sound deterrent.
If noise is coming from a certain direction, you can take steps to insulate that particular area without soundproofing the whole room.
Make sure to seal any cracks between the window and the wall.
The best solution is to use acoustic caulk to seal any gaps, keeping the sound waves on the outside.
Despite the name, green glue is not a glue but a compound that effectively converts sound into heat.
It is applied to the inner surface of a rigid material such as drywall and dries completely within 30 days. It is designed for interior use only.
Green glue should not be used on soft materials, glass, plastic, or metal.
Green glue has been proven to improve STC wall ratings: it is ideal for use in a home theater.
Solid Core Doors
Solid doors do a much better job of keeping out noise than hollow core doors.
Again, this is because the denser the mass, the more soundwaves have a problem penetrating.
Wood is not a good sound conductor, and the waves will be absorbed into the timber.
Solid doors are usually not made from a single slab of wood but comprise a frame with panels attached.
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They are more expensive than hollow core doors but are also long-lasting.
Sealing and Weather Stripping
The finishing touch to soundproof a door is to add a seal around the frame and between the door and the floor.
You can use a number of materials for this e.g.,
- Foam tape
- Rubber tubes
- Sweep strips
- Tension seal
Some of these options are longer lasting than others — felt, and foam tape will need to be replaced regularly.
Soundproofing the Interior of a Room
There are many options for soundproofing inside a room, some more effective than others.
If you have some DIY experience, you could build a wooden frame that contains foam panels to hang on the wall: foam is an excellent sound absorber.
You could make your own wall hangings and drape them on rails attached to the ceiling.
You could put down a few scatter rugs, a carpet, or floor tiles — the thicker, the better if you want them to absorb sound and keep your feet warm.
Hanging panels made of toweling on the back of the door will help muffle sound from that direction.
There are dozens more commercial products on the market that are attractive and practical.
It is almost impossible to soundproof a room completely, but there are many steps you can take to minimize noise pollution.
Some are more expensive than others, and some are more effective than others.
With a little thought, you should be able to create a quiet and comfortable environment in that you can take refuge.
Robert is an electronic engineer with more than five years of experience with a solid affinity for helping people reduce noise. He writes about these silent home appliances and easy soundproofing measures to help everyone avoid the negative effect of extended exposure to high noise levels.