The overwhelming need for affordable housing has kept many developers awake at night trying to figure out the next cost-cutting move they can make to keep their prices reasonable despite the hardships being faced in today’s pandemic-ridden economy. Their sleepless nights are finally catching up with the rest of us as their decisions, more specifically the now popular idea of thin, hollow walls between adjacent apartments are now keeping everyone awake. One can listen in on a conversation happening next door from the comfort (or discomfort) of their living room.
Because sleep was clearly out of the question, we took the time to research how to reduce noise through walls in a bid to improve the acoustic quality in our homes. What follows is an overview of the structural weaknesses through which noise penetrates our walls coupled with 7 ways we learned to fix these gaps and suggestions of tools you can use to fix them.
Identifying the Point(s) of Weakness
Identify the type of noise you are hearing before you get confused by the wide array of soundproofing material, methods, and techniques at your disposal. This way, whichever move you make will be focused and effective, and you will not waste your time and resources on projects without impact.
The 2 main categories of sound are airborne and impact sounds. Airborne sounds are moderate to high-frequency sounds and usually transmit from place to place via airwaves. Impact sounds are lower frequency sounds and transmit through the vibration of physical objects. Knowing how the noise gets in is a key step towards reducing it. You may discover it is coming in through other avenues besides the wall and should be handled separately.
How to Reduce Noise Through Walls
Once you have established the source of noise and confirmed it is coming in through the wall, there are 2 general approaches you can take to reduce it. These are not mutually exclusive and should be applied together for the best results.
Sound Blocking or Insulation
Sound blocking or sound insulation refers to the material and techniques used to restrict unwanted sound from traveling between separate spaces, like from one room to another or outside to inside and vice versa. Sound travels in the form of vibrations through the air and physical substances. This solution involves a physical barrier that either deadens each sound wave or confines noise pollution to its side of the divide.
Sound Absorption or Diffusion Sound absorption of diffusion is reducing the amplitude of the soundwave by converting some of the energy into heat which easily dissipates instead of transmitting it as it is. The end effect is to lower the intensity of sound. Absorption needs soft and supple material that will not resist or reflect the soundwave but will allow its acoustic energy to flex or vibrate them. This is how the soundwave loses energy.
7 Effective Ways to Reduce Noise Through Walls
We are now going into the specific actions that you can take to combat distracting noises. They are just different ways of sound insulation and diffusion using diverse tools.
1. Seal Every Hole On Your Wall
A tiny hole can have a massive impact on sound reduction because sound travels through the air, and air can get through it. It is not uncommon to have holes on your wall that you are not aware of, as some of them are tiny beyond the scope of the naked human eye. These holes may be attributed to wear and tear if it is an old building, or they may be an unintentional byproduct from the building’s construction days as unused wiring and plumbing. To reduce noise passing through walls, you need to seal these cracks with a sound-blocking material.
The air vent is another opening on the wall through which noise will transmit. If you are sealing the walls, you might as well seal the vents, or you won’t get all the benefits. Sealing the vents interferes with the airflow, and you need to ensure you’re okay with this before starting the process. There are, however, ways to avoid sealing off the air vent completely; You can cover it with acoustic material like a curtain or blanket, add sound absorbent material inside it to create a sound maze or fill the opening with an acoustic sealant.
Acoustic caulk is a soft and pliable spray foam used to cover edges and seal holes and gaps on walls, ceilings, windows, and doors for soundproofing purposes. It maintains its softness and flexibility throughout, allowing it to fit snugly in these crevices for an airtight seal that sound can’t penetrate.
Green glue is a sound damping compound in the caulking class created using a special polymeric formula that converts mechanical energy from soundwaves into small heat pockets, dissipating the noise. It forms a damping system when applied to those gaps and holes. You can also use it between layers of building materials, like drywall, to diffuse structural noise.
This acoustic material is easy to apply, seals within minutes, and will be completely dry within 48 hours. Its ability to retain elasticity ensures it will stay put for days without cracking so your seal stays intact.
2. Using Furniture to Fill Out Space
Prop furniture against the troubling wall, ensuring it doesn’t touch the wall to leave an air gap for sound absorption. Use the largest pieces of furniture you have for this exercise. It will work much better if the furniture is upholstered using plush fabrics like corduroy, chenille, or suede. These will absorb sound and reduce the intensity of reverberations, turning down the noise significantly.
For optimized results, add soundproofing material between the furniture and the wall. These should block both structural and aerodynamic sound waves from transferring to the furniture from the wall. Hang acoustic panels, curtains, or blankets behind the furniture to facilitate this. As much as blankets can be unsightly wall hangings, you may have to figure out a way to incorporate them into your interior design. They won’t be visible behind a towering bookshelf though.
Arrange the room so that soundwaves don’t reflect on hard surfaces, as this enables reverberation and increases the intensity of the sounds in the room.
This sound absorbing blanket is easy to use for many reasons; it has 9 grommets on one end for easy hanging, it is machine washable, and can be hung to dry. The durable cotton and polyester blend adds mass to the blanket, so it naturally absorbs sounds. At 96 by 80 inches, it is sufficiently huge to cover an entire section of the wall to handle problematic noises
3. Soundproofing Painting
This special water-based insulating paint is heavy-bodied because it contains tiny sealed vacuum cells with sound-absorbing and insulating capabilities. The cells’ soft pigments vibrate upon contact with soundwaves and release some energy as heat, dampening the sound intensity. The cell membranes also deflect noises and prevent them from coming into contact with the wall properly. This reduces the structural transference of sound. The paint is also dense enough to plug the small openings on the wall where sound carries for better noise management.
Sound proof paint is, however, not very effective in reducing wall noises on its own, it will absorb mid-frequency sounds like normal human conversations from noisy neighbours, but it is not thick enough to handle louder external noise, high or low frequencies.
Ensure every inch of the targeted wall is covered with paint for maximum effect, and apply more than one coat. Three coats are recommended, but it takes longer to dry, so you shouldn’t be in a hurry. You don’t need to apply it to the entire house, just identify the problem areas and focus on those, so that you can be generous with the paint.
4. Hang Acoustic Curtains On Problematic Walls
Acoustic curtains are also called sound dampening curtains. They resist vibration and reduce sound transmission. The larger the curtain is, the more area it covers, the better the degree of noise attenuation it can facilitate. The curtain folds provide extra sound capturing space, and the more it folds, the better the overall noise reduction effect. It should cover the entire wall from the ceiling to the floor for optimized results, so endeavor to get them long and wide to optimize results.
The ideal material for acoustic panel curtains is lush and generous; polyester, suede, velvet, or satin are excellent examples. The best acoustic curtains have double or triple layers of fabric and are heavy, so their density and mass are sufficient to block and diffuse sound waves and outside noise.
You should use a reinforced curtain rod so it can bear the weight. Go for machine washable fabrics that can be hung to dry, so you don’t need to deal with expensive and overly engaging maintenance processes.
It is fair to point out that even the best acoustic curtains are not guaranteed to block sound completely on their own but will greatly reduce its intensity, especially for lower decibels. Like all soundproofing methods, the curtains will deliver much better in combination with other tools.
This double-layered noise barrier curtain is woven using triple weave technology that infuses yarn between two layers of fabric. NICETOWN has released its own decorative curtain rods to match with their curtains, so you no longer have to guess if the rod will have sufficient power to hold the heavy curtain. Each curtain panel has silver grommets for easy installation and sliding. They are also machine washable, making maintenance a breeze for any user.
5. Soften The Surfaces
By doing this, you reduce the soundwaves landing on the hard wall and reflecting right back into the room with the same reverberation. It also enables you to provide a healthy amount of sound-absorbing material for acoustic clarity within the room. Empty spaces and hard surfaces enable reverberation, which increases the intensity of noise within the room, making it more probable that the noise will permeate the walls. They also amplify noise that has already permeated into the room.
Wall softening material includes various forms of acoustic panels, tiles, blankets, and inserts. It also includes wall hangings like paintings and furniture, which we already discussed. The type of furniture you have affects the level of surface softening required as well as the optimum placement of wall-mounted acoustic material. Softening surfaces might require a bit of rearrangement of the room. Pay special attention to the problematic spot you should have already identified.
They are mounted on the wall to prevent sound from hitting the hard surface directly and reduce reverberation because of their soft and rubberlike texture. They also stop noises from outside the room from getting into the room, lowering the overall intensity of noise in the room. They can be attached to the wall using hook and loop strips or adhesive. They can also be deployed on the ceiling for the same purpose, but that is a story for another discussion.
The composition of acoustic panels changes from product to product, some have specialized in absorbing echoes within the room and deadening reverberations while others are better placed to block sounds from permeating into the room. Sound-absorbing acoustic panels are light by nature due to their soft and open pores, while the blocking panels are heavier because you require mass and density to block sound. There are acoustic panels that can deliver both services commonly referred to as composite panels in the soundproofing field. To be honest, all acoustic panels absorb and block soundwaves simultaneously, the degree of functionality is what sets them apart from each other.
They are often fabric wrapped to blend better with the household décor. The acoustic material ranges from polyurethane fiberglass to extruded melamine foam and, in some instances, perforated wood. They are usually cut into tiles, so they are easy to deploy on specific spots as the need arises.
The nature of the surfaces also plays a role in their effectiveness, depending on the source of the noise. Some acoustic panels have smooth surfaces while others have uneven cuboid shapes, waves, grids, wedges, cones, pyramids, or egg crate designs. While smooth surfaces will still help in blocking and absorbing sound waves, they can easily reflect them. The raised elements of textured panels dissipate the waves, making them more effective.
The different textures also have their own unique strengths and weaknesses. Egg crate shapes are easily available and pocket-friendly. Wedges have great sound absorption, but they need to face the direction of the sound to be effective, limiting their utility in large spaces. Pyramids with pointed tips absorb sound from all directions but struggle with lower frequencies. Consider using a combination of different textures to get the best from each.
You can use these tiles for spot treating and wall décor because they come readily separated, and you can apply the 12 pieces in different places. The tiles are uniform in density and firmness, so the effect will be similar. The serrated texture will deaden unwanted reverberations and echoes for a clear, crisp sound.
We can’t discuss softening the surface without touching on soundproofing blankets. They cover larger surfaces and are efficient in sound dampening because of their composition. The thickness of the blanket and how it is stitched bears on its performance as a soundproofing material. If your walls are naked with many empty hard surfaces, then this is a better solution than acoustic panels, which are costlier and will take longer to set up.
An excellent soundproofing blanket will feature a woven fabric exterior covering sound-absorbing material like fiberglass, mineral wool, cotton, or cellulose. The idea is to allow the soundwaves in and trap them long enough to lose their intensity. Your average acoustic blanket is heavy, and you might need some help setting it up. They often come with grommets to facilitate easy installation.
If a proper acoustic blanket is above your budget allocation, you have the option of using moving blankets which movers use to pack your stuff when you are moving. As much as they will not get the same results, they also can absorb sound. Layering one over another will also get you closer to the ideal density.
6. Insulate interior walls
Insulating interior walls is most critical if you have those hollow stud walls that are common nowadays, and it is facing the source of the noise you are trying to avoid. The hollow, thin boards are not sufficient to keep, absorb or even block sound. Insulation helps in regulating heat and the new thickness of the wall courtesy of the insulating material improves its ability to dissipate and absorb sounds.
Your choice of insulating material has a huge impact on the acoustic value addition the project will provide. You can opt for batts made of fiberglass, mineral wool, or foam to line up the space inside the wall. Besides adding mass to the structure, these materials are excellent sound absorbers. Ensure the batts fit snugly between your studs, and there are no hollow bits or airspaces that can transmit sound.
You can also use Mass Loaded Vinyl (MLV) supported by the studs in a way that doesn’t come into contact with the external or internal board. It dissipates sound and decouples the two sides of the wall as we shall see in the next section.
There is also the option of inserting thermal panels with sound blocking capabilities due to the extra mass they will throw in between the two sides of the wall.
The rugged construction and thermal insulation properties make this foam panel the ideal material for insulating your hollow wall. It is a layer of closed-cell foam bonded between a metalized aluminum polyester film and textured white vinyl. It doesn’t compress, collapse, or disintegrate, so you will not worry about monitoring what is going on inside the wall. It is also impervious to fungi, mold, or mildew.
7. Decouple The Wall
This process involves mechanically separating your internal wall from the exterior wall so they are independent of each other in terms of vibration and structural transmission of sound. It solves the impact noise problem and if well-executed, can also solve take care of airborne noises. It is the most effective of all the solutions we have proposed but also the most technical and time-consuming one. You might need to seek assistance from an expert, and the required modifications may have to be sanctioned by the building owner(s) and/or regulatory authorities.
Noise Reducing Drywall
Drywalls are multiple dense gypsum cores separated by layers of viscoelastic polymer, which creates an efficient sound barrier. You can layer up the existing wall with 1 or 2 extra drywalls to add mass and density. This makes it hard for soundwaves to go beyond your wall if it is done properly.
Gypsum on its own is a hard material, and its rigidity will have the drywall vibrating along with the main wall, allowing soundwaves to pass through and even structurally transmitting some of it. If you are using standard drywall, you will need to introduce a soft soundproofing material in between the wall and your drywalls to dampen the sound. You can apply green glue using a caulking gun or use noise-reducing foam for this.
Mass Loaded Vinyl (MLV)
This is a heavy but very limp sheeting made from materials like plastic, ceramic, and metal. The extra weight and extra flexibility make it a very efficient soundproofing material. It can be deployed on its own or along with the other methods mentioned in this article. You can install MLV directly on the problem wall using adhesive or inside the wall between studs, where it does its job without being visible.
MLV doesn’t add any aesthetic value to the room. It will be best to find a way to hide it if you are applying it on the wall directly. You can place furniture in front of it, cover it with curtains, acoustic blankets or install the soundproof foam on top of it.
MLV can be applied in between walls to facilitate decoupling. It is thinner without compromising density, so you will save on space in between your drywalls.
The best cocktail of solutions for reducing noise transmitting through your walls is unique to every situation. There are internal and external influences that are hardly identical. Understanding your problem and limitations is key to finding a lasting solution.