Building materials and acoustics play important roles in designing and constructing spaces that perform as intended. Whether it’s creating great sound for music in concert halls or quiet exam rooms for medical offices, good acoustics are key.
Some materials absorb sound and others block it. To block sound, acoustical specialists add materials such as mass loaded vinyl barriers and gypsum wallboard that decouples the walls from each other.
Insulation
Insulation is a common way to reduce energy costs, and it is also one of the best ways to protect a building from noise pollution. Many insulation products are made of recycled materials, including cellulose, fiberglass and mineral (rock or slag) wool. Look for the NRC rating when selecting a product—it indicates how well the material reflects or absorbs sound.
Polyurethane foam is a common option for sound insulation because of its great sealing capacity. It can be sprayed into wall cavities or attics, creating a blanket of insulation that helps prevent sound from traveling between different levels of the building.
Steel is a very dense and massive material that has excellent acoustical properties—it absorbs sound rather than reflecting it. However, it is expensive and is usually used in structural components. There are new absorptive glass-like materials that have been developed that are similar to Plexiglas and have the ability to absorb a significant amount of sound.
A material’s acoustic properties are heavily dependent on its density and weight. For example, lightweight concretes like CRC that incorporate a high percentage of crumb rubber have a better acoustic performance than normal concrete due to its lower density and reduced surface reflection. The compaction degree of a concrete is also a key factor in determining its acoustic properties. The more compact a concrete is, the better it is at absorbing sound energy.
Walls
A wall is a material that separates you from the outside world and can keep sound from entering or exiting a room. Most walls are made of a breathable material like brick or cinder blocks, but some are also constructed of thicker materials such as plywood or OSB sheathing. While breathable materials are good at absorbing sound, they can be difficult to work with. In particular, they do not provide as much structural rigidity as wood framing.
When a sound wave in air hits the surface of a material, some of the energy is reflected and the rest passes into the material. The material’s density determines how much energy is absorbed, but even more important are its characteristics and how it is built. For example, a rough surface absorbs more sound than a smooth one, and a porous material like clay or mud absorbs more than a dense material such as brick.
A brick wall can be soundproofed by adding acoustic insulation, sealing leaky areas and reinforcing the mortar joints. This can decrease sound transmission into and out of the brick space, and help meet building codes for acoustics. In order to be considered soundproof, a wall must achieve an STC rating of 45 or higher when tested using the ASTM E90 method. The higher the STC rating, the better the sound insulation.
Ceilings
A ceiling is an overhead interior surface that conceals the underside of a floor or roof and is a popular location for decorations. The ceiling is also a good place to hide pipes and other elements of the building structure. In addition, ceilings can help control sound reverberation.
Ceilings have a more significant impact on a room’s acoustics than walls because they cover a larger area. They play a critical role in controlling sound propagation and optimizing speech intelligibility.
When acoustic ceilings are designed with the right materials, they can reduce distracting noise from adjacent rooms and limit the transmission of vibrations between floors and walls. These acoustic ceiling materials can be molded to match the shape of a room, eliminating echoes in open spaces and creating more private environments.
Acoustic ceilings are available in a wide variety of styles and colors. They are also made from a variety of materials, including glass-fiber-reinforced gypsum board and plywood. There are even ceilings that are woven fabric or latex faced fiberglass that simulate the look of painted drywall. In some cases, ceilings are made from timber, a material that is attractive to many clients because it provides a unique design element to the space. Ceilings that use wood also help reduce the amount of noise that can travel from one space to another. This sound can be caused by footsteps, squeaky furniture and more.
Floors
The floor of a room is the surface that supports the occupants and other furniture. It is generally made of concrete or a hard material. It may be as simple as dirt in a cave or many layered with different materials using modern technology. The floor of a building is usually covered with either concrete, stone or wood.
A concrete floor is very strong and durable. It is often used in the basement and is good for sound control. It is also easy to clean and maintain. Bricks are an alternative to concrete and are a good choice for floors in unimportant rooms and godowns. They are inexpensive and have good thermal insulation properties. Mud is another good flooring material which can be made from moist earth with chopped straw or cow dung. It is cheap and has good soundproof properties.
For wood or timber floors, damp proof course is a must. For floors above open attics, insulation under the floor is important as impact noise can travel up thru the ceiling. Polyurethane foam underlayment is an inexpensive option that offers a little insulation beneath new flooring and helps to reduce impact noise. However, it is not as thick as other options and does not provide a complete barrier.