Noise can cause significant problems. Whether it is a noisy neighbor, a home workshop or a home studio, keeping sound from interrupting sleep or disrupting the concentration of someone who is trying to study can become a major necessity. You can block the noise from entering or going out of a room by making it sound proof. This guide will show you the various methods that can be used to sound proof a room. Let’s get started by considering some of the characteristics of sound.
Sound Is Like Water
The best way to think about sound is to imagine throwing a stone into a pond or pool of water. Near where the stone sank into the pool, the waves created are closer together and more intense and they spread out and become less intense as they move further away from the point of impact. If an object is in the path of those waves, the waves will strike the object on the side facing the point of impact, object will absorb much of their impact and the rest will travel around it. The space on the opposite side of object from the point of impact will remain undisturbed by the waves which the stone created.
Sound works in a similar fashion to water. The source of a sound is similar to the point of impact of the stone. Sound travels in waves of vibration from the source outward in all directions. Closer to the source, sound is more intense and the waves of vibration are closer together, but as they move further away, they grow less intense and the waves of vibration are farther apart. When sound waves meet a soundproof object, they are absorbed and the space on the other side of the object is not affected by those waves of vibration.
Essentially, sound proofing a room is nothing more than placing objects that will absorb sound waves and allow the space beyond the object to be free of those sound waves or sound proof. With this concept in mind, let’s begin to examine various methods of sound proofing a room.
Soundproof Blankets or Curtains
One of the least expensive and simplest means of soundproofing a room is through the use of acoustical blankets or curtains. These products can be hung over windows and doors to help with soundproofing, or they can be hung along the surface of walls to help absorb sound. Sound proof blankets and curtains typically have two layers of fabric with some form of insulating material in between. The type of fabric, the insulation material used, their thickness, length and pleats are what determine how effective they will be at absorbing sound. Here are the various components of sound proof blankets or curtains:
• Fabric. The typical fabrics used are suede, velvet, wool or velour and tend to be 32 oz. or greater weight per linear yard. These types of materials have tons of tiny sound traps in them to help with absorption.
• Insulation. Foam, cotton, wool or polyester quilt batting, or fiberglass may be used between two layers of fabric to help absorb sound as well.
• Pleats. Pleats help to absorb mid-range and high frequencies. For pleating to be effective, the curtains need to be 1.5 to 2.0 times the width of the surface they intend to cover. This provides 50% to 100% pleating, which also helps to trap and absorb sound.
• Length. Length is important because sound is like water and will seep through the path of least resistance. Any cracks at the top, bottom or between curtains will be a route for sound to slip through.
Though noise reduction or acoustical curtains are the least expensive option to a major remodeling job, they have their limits as to what they can accomplish. At most, you can expect a reduction of 20 dB of noise reduction with well built acoustic curtains and not more than 10 to 15 decibels from typical sound proof drapes. If you need greater noise reduction, you will have to do a whole lot more than hang curtains.
Soundproofing Walls, Floor and Ceiling
This is where we get into the meat of soundproofing. Regardless of which of the three surfaces of a room you are discussing, soundproofing works the same way. Sound absorbing material must be added to those surfaces to prevent the movement of sound from one side to the other. Let’s look at the various surfaces and the various methods of soundproofing them.
Soundproofing the Ceiling
Soundproofing a ceiling isn’t a great deal different than sound proofing a wall. In most cases, all that is really needed is an added layer or two of drywall with dampening glue between the layers. In situations where the ceiling is heavy concrete, such as in apartment buildings, these added layers of drywall won’t do a lot of good. In these instances, you will want to create space between the concrete and the drywall with fiberglass insulation between the two. You can create a ceiling similar to what we will show you with walls in a moment or you can hang your ceiling and use acoustical tiles, like many institutional buildings, especially schools and hospitals use.
Soundproofing the Floor
If you are creating your soundproof room on the lowest floor of your home or the building where you live, there is really no point in soundproofing the floor. However, if you are trying to keep sound from entering or escaping your room, you will need to soundproof the floor as well. Most of the discussions of this article surround eliminating airborne sound, but with floors, impact noise becomes a major factor. Impact noise is much more difficult to eliminate.
For reducing impact noise, acoustic matting is laid directly on the subfloor and then covered over by whatever flooring is to be used in the room. In addition, a floating floor can be used to provide a pocket of insulation between the floor and the subfloor. You might run across floating floors in gymnasiums where wood flooring is laid over heavy-duty rubber knobs. In a gym, this is to create spring in the floor, but for soundproofing the added space helps to diffuse sound.
Soundproofing walls is usually where most efforts are put into soundproofing and where you will spend more of your cash as well. There are a lot of different ways to soundproof walls, so we’ll break each of those methods down and look at them individually.
Depending on how your soundproof room will be used, one of the best methods of soundproofing is adding bookshelves. Books, especially hundreds of them all lined up together on bookshelves, absorb loads of sound, because of the material they are made out of and the millions, or perhaps billions, of sound trapping pockets are contained in them. An entire wall or two of bookshelves from floor to ceiling packed full of books will absorb more sound than almost any other soundproofing method. Of course, this only works if you are soundproofing the room for use as a study or a bedroom.
Adding Mass to the Walls
The most common method of soundproofing a wall is to simply add more mass. Just as we described when we discussed ceiling above, a simple and effective way to soundproof walls is to add a layer or two of drywall with dampening glue between the layers. If the walls you are adding mass to are insulated drywall to begin with, this will be effective at soundproofing the room. If your walls are concrete or masonry, this method won’t accomplish much. In these instances, you will need to fur-out the wall, and add insulation before installing the drywall. There are several ways to accomplish this, but here are the two most common ones:
• Furring channels. Often called hat-channels because a cross-section resembles the shape of a hat, these channels can be attached to masonry or concrete walls. Between the hat channels, 1 ½” insulation can be added before two layers of drywall with dampening glue is attached to the hat channels.
• Adding a stud wall. What you do, essentially, is build another wall just inside the existing wall, leaving approximately 1” gap between the studs and the existing wall. A couple of advantages to utilizing this method is that it is pretty simple to do and you only have to drill a few pilot holes for screws into the existing concrete or masonry wall to anchor your stud wall to rather than a lot of holes like with hat channels. Stud walls also allow you to add thicker insulation between the studs before installing your drywall.
These are the two most common ways of adding soundproof walls inside of a room that is surrounded by concrete or masonry walls. Though the first will achieve a level of soundproofing, the second is the more effective, though more expensive solution. Acoustical curtains, blankets or additional acoustical treatment can also be added after completing either of these methods for some additional soundproofing, but in most cases, they won’t be necessary if you have plenty of sound absorbing insulation between the existing wall and the surface. Let’s take a closer look at insulation.
We just discussed adding a stud wall or furring out a concrete wall, where insulation can be added between the existing wall and the new all. Soundproofing is simplified a great deal if you already have a stud wall to work with. In such instances, you will only need to remove the existing wall finish, insert insulation between the studs and then add your new drywall layers with dampening glue between them. Regardless of what treatment you are able to use, you will need to pay special attention to installing insulation, even in the ceiling as we mentioned earlier. Let’s take a closer look at some of the common insulation materials used for acoustic insulation:
• Fiberglass. Often called Glasswool, fiberglass insulation comes in rolls and is unrolled, cut and attached between studs in the floor or ceiling or simply placed on top of a suspended acoustical ceiling. Fiberglass is common for thermal insulation because of the fibrous pockets that are created within the material. Those fibrous pockets trap sound the same way they trap air.
• Acoustical Foam. This type of insulation is a special type of foam made in various densities and various thicknesses. It comes in rolls like fiberglass or in panels and can be used to fill the space in your stud wall, furred out wall or above your acoustic ceiling panels.
• Mass Loaded Vinyl (MLV). MLV is often added in thinner furred out spaces or laid over the top of other insulation to create an additional soundproof layer. Just as its name suggests, foam is loaded between two layers of vinyl. This is a very effective insulation to add, especially if you are working with limited space.
When you consider insulation for soundproofing, there is one form that you ought to stay away from; blown insulation. Where this type of insulation works well as thermal insulation, it is not effective when it comes to sound absorption.
Specially Designed Acoustical Materials
Creating a new wall inside of an existing wall or furring out a wall with hat channels and adding insulation and additional drywall sheets are not always the best solution. There are some drawbacks, such as: cost, labor intensity and loss of living space. Alternatives to a full remodel and renovation projects include the use of specially designed acoustic materials.
Acoustic hangers are often used during the construction of spaces that are specifically designated for noise reduction. Often referred to as soundbreaker bars are designed to both absorb vibration and reduce the surface area contact between two surfaces. These bars are typically thin lengths of metal to which plasterboard or acoustic panels are attached. These sound breaker bars are only about ½” thick, so the loss of space is far less. They work in a similar manner as the hat channels we mentioned above, but are specifically designed acoustical materials.
Acoustic Wedge Panels
These panels are often seen inside recording studios because they are very effective at absorbing both high and low frequencies. They tend to come in 12” x 12” panels and have a 2” curve depth relief. They typically come with already attached adhesive pull strips which make them easier to install. You will want to apply 3M adhesive spray to the walls or ceilings where these wedge panels are to be installed before attaching them. Wedge panels that have a high concentration of fiberglass in their composition are the most effective and give you the most soundproofing value for your investment.
It might be hard to imagine, but damping compound or damping glue is something of a magical substance. Besides being a super sound absorption material, it converts sound energy into heat. Dampening compound is especially effective at absorbing low-frequency noise, like that thundering bass that seems to penetrate through all other materials. You need to keep in mind that noise proofing glue, calking, viscoelastic adhesive and materials utilizing this dampening compound take several days, and even up to weeks, in order to cure and reach their full potential.
A weak area in the damming of sound is found at the doors into your soundproof room. After all of the effort you have put into soundproofing your room, if you ignore the doors, it was all for not. Sound proof doors are typically insulated with the very best acoustic insulation inside of an otherwise hollow-core door. In addition, sound wedge panels can be added to the inner surface of the door to increase its soundproof effectiveness. You can’t forget the crack under the door either. This can be accomplished by the installation of a rubber loop sweep that is attached to base of the door. If the gap is excessive, you might have to attach an additional strip of wood to the bottom of the door in order to make up some of the gap.
Filling in the Cracks
Just like water, sound will search for the tiniest point of resistance and flow through that weak space. Those cracks tend to be around windows, doors and corners. Let’s take a look at some of the additional steps you can take to completely seal off all sound. Just like you would caulk around a bathtub of sink to off water leakage, you need to seal off all cracks and seal all areas where sound might leak through. The installation of caulk that is made with the dampening compound we already discussed can be used to make sure that not a single “drop” of sound is able to enter or escape
Regardless of whether your goal is to keep sound in or keep sound out, soundproofing a room can be a daunting task unless you know what you are doing. Given the information and methods we have just supplied in this article, you should be better qualified to accomplish the task of soundproofing any room in your house, office, shop or wherever you might have need a reduction in noise. Dive right in and soundproof your room for the sake of tranquility for all.