A door like a window can be a portal for noise or unwanted sound to enter our room. Acoustic doors have to perform a dual function. They must provide a barrier between the inside of the room and the outside noise levels. They also must keep sound energy generated from within the room from leaving the room and entering other adjacent rooms. They must do this on a temporary basis because they must open and close to allow for individual access into and out of the room. As they open and close continually, they must seal correctly, so that no gap exists between the door edges and especially the door bottom.

There Is s No Substitute For Mass

Our door through its use of barrier technology must have mass. Multiple layers of materials arranged in vibration reducing manners is the goal. Multiple density fiberboard (MDF) is a good material that provides us with the mass we need to begin our door construction. Remember from past discussions, that not only do we need mass in our material selection but we need to have different materials with different densities, so we can slow down vibrations coming through our door. Vibrations will lose energy if they have to struggle through different material types with different densities. If we use MDF, we can mate it with a plywood. Plywood has numerous layers that are fitted together into a single piece of material. Now we have two different materials that provide us with the appropriate densities.

Proper Assembly Required

We need to take our MDF and plywood and then assemble these two materials in a manner that reduces vibrations. Sound produces and is produced by vibrations. When electromechanical sound from our loudspeakers is produced and strikes our door surface, it is turned into vibrational energy. This mechanical vibrational energy sets the surface it strikes into motion. When it strikes our door, our door must be made in a manner that allows for this to occur, but reduces the vibrations through the way it is assembled. To reduce these vibrations, we use a process termed constrained layer mass damping to sandwich our chosen materials together.

Constrained Layer Mass Damping

Constrained layer mass damping is a process where we take different material types with different densities and arrange them in a manner that keeps vibration reduction in mind. We sandwich each material together with another material such as an acoustical glue. The more materials the vibration has to go through, the better for its reduction. With our MDF, plywood, and now glue, we have three materials that vibrations must go through. The more the better to a point.

MDF / Plywood

If we place MDF as the outside of our door surface, we then can add our plywood underneath the MDF. To secure the two materials together, we need to glue them together. We use an acoustic glue that will keep both materials together and provide another material type with a different density that our unwanted vibrations must go through. If we use MDF on the other side of the plywood we should use a MDF piece that is a thicker or not as thick piece as the front piece. Remember, we want to vary the density or mass of the piece and the thickness of the material to further “confuse” the vibration. We should have as our acoustic goal to have our finished door weigh at least 9/lbs./sq.ft. to provide the necessary noise stopping power.

How to Hinge

Once we have our door assembled with its associated weight, we will need to place it into the door frame. If it is an existing door frame, we must make sure it can support our new acoustic door’s weight and then seal correctly around all door edge surfaces. We may want to consider building a new door frame to support our new door. If we do not and choose to keep our existing frame, we must be sure it is sealed to the existing room structure with a healthy application of acoustic sealant.

To support our new heavy acoustic door, we will need hinges. A cam lift hinge will work well in this scenario. A cam lift hinge will assist us in proper sealing due to its construction method. A cam lift hinge can also support the weight of our new acoustic door. Numerous finishes are available on cam lift hinges to accommodate any decor.

Seal All Gaps

Finally, we must seal our new door to the door frame. All door edges must close squarely and seal properly. Special attention must be paid to the bottom of the door. This is an area where their is a lot of wear and tear and providing a continual seal every time is a must. We can use a brush type sealing strip that collapses when the door is opened or closed but then springs back into place to provide a good seal. There are numerous sealing strips available. Care must be taken to choose the correct stripping that matches the use of the door and the acoustical objective.

A door and window can be the weakest link in our room. We must use mass in our door to stop vibrations. We must assemble the materials in a manner that reduces vibrations and we must sure it seals correctly every time it opens and closes. It must be the correct mass and stiffness and be able to achieve a sound transmission class rating of at least 55.

Sound proofing our ceilings is probably the most difficult part of our room to deal with, simply because we have to support any material type we decide to use with our existing ceiling or by building a new structure. If we are dealing with a lot of noise from adjacent rooms, we will need to measure how large of a noise problem we actually have, so we can figure out exactly how much material we need to use. We definitely don’t want to use any more material than the noise issue demands since we have to support any material we will use with the existing structure or build a new one.

Measure The Problem

Our first task is to measure how much noise we have to deal with. If our noise is coming from our own room and we need to seal that noise from drifting into other rooms, we need to measure the noise from within our room and start with that issue first. If the noise is external to our room, we need to measure it and find how much of a noise issue we have to deal with. Remember from past discussions, that both noise sources whether external or internal require different forms of acoustic treatment. Barrier technology is used to keep noise from entering our room from external sources and also keeping our own noise levels generated in the room from “bleeding” into existing structures. If we need to control room boundary reflections and general small noise levels within our rooms, we can use absorption technology.

If our noise levels are determined to generate from external causes we will need to use barrier technologies to place a barrier between us and the noise. Once we have determined how much noise we have to isolate ourselves from and at what levels we are dealing with, we can choose the appropriate barrier materials and technology we need. All barrier materials have mass and weight associated with them. Barrier technology is all about controlling vibrations from sound pressure waves that are produced by our noise source. Mass and high density materials have to be arranged in a certain vibrational controlling method termed constrained layer mass damping. Multiple layers of materials with different densities are arranged in a manner that produces the least vibrational transfer of energy.

Build a Noise Barrier

To build a barrier for our ceiling, we will start with two commonly found construction materials. We can use plywood and drywall or gypsum board. We can start by taking our plywood piece with a 1/2″ thickness and then placing an “acoustical glue” between the plywood and the 3/8″ layer of drywall. Acoustic glue never hardens completely and the two materials that it is bonding with “float” against each other. This layering of materials technique is termed constrained layer mass damping.

In a constrained layer, mass damping configuration, all layers of high density materials must be separated or mechanically decoupled from each other to minimize vibrations from transferring from one piece of material to another. By isolating each higher density piece of material with a lower density or viseoelastic damping compound, the vibration must travel through all of these materials and as it does it losses energy and this is our goal. If we can reduce the vibrations strength, then we can minimize the sound or noise energy that vibrations can produce.

To further increase our barrier’s strength against vibrations, we can physically arrange the materials in ways that will reduce vibrations. If we are using multiple layers of plywood, we can arrange one piece of plywood one grain direction and position the other in a cross grain direction from our original piece. This running of the grains in different directions can go a long way to assist us in reducing our vibrational levels.

Installation Is Critical

Installing our new barrier technology requires care and careful consideration. We must install our new ceiling in a manner that continues our vibrational isolation theme. We must separate the new ceiling from the old or existing one using vibration isolation techniques. We first install a series of isolation tracks that our new ceiling will attach to. These tracks will physically decouple our new ceiling from the existing one and create an air space between the old and new ceiling. Air is also a vibration reducing material and can be effective as another layer for vibrations to have to work themselves through.

Watch Those Edges

We must pay particular attention to the edges of our new ceiling. In most ceilings, the ceiling edge surfaces touch the existing walls. There is no gap or space between the edge of the ceiling and the wall surfaces. While this looks nice in normal environments, it can be detrimental when dealing with vibrations that contribute to noise. Our new ceiling or barrier must have itself physically isolated from our existing room structure by leaving a gap between our new ceiling and existing wall structure. This physical gap serves two purposes. First, it isolates our new ceiling from the walls which will prevent the vibrations from our walls from entering our new ceiling barrier. Secondly, the small gap will prevent vibrations from our ceiling from entering into the walls and causing more issues. This small gap will be filled in with an acoustical sealant.

Absorption Inside Our Rooms

Noise levels in our room can be controlled through the use of absorption. We can absorb excess low, middle, and high frequency energy inside our rooms using many different types and forms of absorption technology. If we have noisy office equipment, we can place these units in sound isolating cabinets. HVAC noise can be controlled by lining our duct work with special foam technology that can reduce the air flow in the duct work itself. We can also reduce the fan noise by lowering the fan speed to reduce air flow. We need to lower the air flow down below 340 feet per minute.

Sound proofing your ceiling is not an easy task. If we have to build a barrier between our existing ceiling surfaces and outside noise levels, we really need a professional to design and install it. One can spend more money and energy making mistakes by guessing how much material to use and building and installing it incorrectly, than it would take to actually have a professional do it. Controlling noise levels within our room using absorption technologies can be a do it yourself project with adequate research done ahead of material selection and installation. `