Incorporating soundproofing materials into your building design can prevent unwanted noise from passing in or out of a room. These materials can also be used to help decouple walls, reduce vibration and enhance speech intelligibility.
Absorbing sounds reduces reverberation and echo, which in turn increases speech intelligibility and improves productivity in office spaces. Soft, absorbent materials like fiberglass insulation and acoustic foam are ideal for absorbing sound waves.
Mass and Density
The ability of a material to absorb or reflect sound waves depends on its density, which is a measure of how tightly packed the molecules are. A material must fall within a certain density range to be effective at blocking and absorbing sound; too high and it will simply transmit or reflect the wave; too low and it will lose momentum and essentially disperse the energy into frictional heat.
The higher the density, the more it will attenuate airborne sound transmission. This is why dense materials such as concrete, brick or steel are used to block sound from passing through walls, floors and ceilings.
In addition to their density, many soundproofing materials are also insulators and offer thermal benefits as well. Some common insulation and acoustic materials include sheep’s wool, recycled cotton, cellulose and fibreglass. These products are not only cost-effective but also environmentally friendly and contribute to a healthier indoor environment.
For example, acoustic foams are an effective acoustic solution for sealing gaps and connections in walls and floors. They can reduce the echo and reverberation of rooms which can cause distracting noise and discomfort. Another option is acoustic fiberglass which provides a similar function with the added advantage of flexibility. It is available in a variety of widths and thicknesses to provide a flexible and customized soundproofing solution for different spaces.
De-coupling
Decoupling is the process of separating structural components so that they don’t vibrate against each other. Decoupling reduces sound transmission and is essential for effective soundproofing. Decoupling can be accomplished through a variety of methods including resilient clips, resilient channels, staggered stud framing and double drywall.
The basic idea behind decoupling is to create a space between the structure of a wall or ceiling so that vibrations don’t transfer between them. The space also helps to diffuse the sound waves and further reduces noise transmission.
A common material used for decoupling is Mass Loaded Vinyl (MLV). MLV is a viscoelastic insulation that has both fluid and elastic properties, meaning it will flow when vibrated but then bounce back to its original shape, much like a drum head. The fluid nature of MLV means that it has a high damping effect which works to reduce the vibrations transmitted through a wall or ceiling.
Another type of decoupling material is a dense, open-cell woven mineral or stone wool insulation such as QuietFibre. These insulation products are designed to fit into cavity walls and work on the principle that sound will be reflected before being absorbed.
Hollow walls are also a source of noise because they trap air that will vibrate when struck. This vibration can travel through the wall and into other rooms or even into the outside world. This is why it is important to have a solid barrier of soundproofing between the two spaces that you are trying to separate.
Sound Absorption
Adding more mass and density to walls, floors and ceilings can deflect and absorb some of the energy of sound waves. However, most of the energy is still transmitted through the structure with a small amount of it reflected and some converted to heat (via vibrations) or lost to space. Absorption reduces reverberation and echoing within a room, which helps with privacy and speech intelligibility.
There are a number of materials that are effective at absorbing sounds, including fiberglass insulation, foam composites, and felt. Felt is a non toxic natural material that has a high resilience and density made of millions of individual fibres. This gives it a good sound absorbency rating and is particularly useful for absorbing high frequency noise such as music, speech and gun ranges.
Other common sound absorbers include cellulose insulation, recycled denim and vinyl sound barriers. These are typically installed inside wall framing directly under drywall and help reduce the transmission of sound between spaces.
Resilient channels and acoustic hangers are also excellent additions to any soundproofing project as they improve the effectiveness of the system. They work by breaking the direct pathways that sound could travel between studs or joists, effectively packing out the airspace which allows sound to transmit through these gaps. They are also designed to be used with any type of insulation, which is important for improving the overall performance of a soundproofing system.
Sound Reflection
When a sound wave hits the surface of a material, some gets reflected, some passes into the material and a smaller percentage gets absorbed. Sound absorption is a key element to controlling sound transmission in buildings. Absorptive materials have a harder, less porous surface that causes the sound waves to rub against each other and lose energy. Using these types of materials can help reduce noise levels in a room and create more peaceful and focused spaces.
Absorbing materials that work well include fibreglass insulation, foam and acoustic panels. Some of these are also used for thermal control. The density of these materials helps to prevent the transfer of heat through walls and other barriers, thereby decreasing a room’s temperature.
Other types of sound absorbing materials feature a combination of irregular surfaces and variations in thickness that control the direction that the sounds reflect. These are known as diffusers. These are commonly used in theatre curtains, blackout drapes and studio blankets to increase acoustic equalisation.
Other sound absorbers use a process called damping to reduce the strength of vibrations. This is accomplished by converting the kinetic energy of the vibrations into a small amount of heat through molecular friction. Recycled polyester insulation is a great example of this, helping to decrease landfill waste and offering impressive sound-absorbing properties.