Soundproofing
Soundproofing is the process of reducing unwanted noise and noise pollution, and in preventing noise from entering or leaving specific areas. Soundproofing materials and products act as silencers, mufflers and insulation, absorbing the excess sound level in rooms, chambers and around pieces of equipment in order to create quieter environments for the purposes of worker safety, product testing, audio mixing and research etc.
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The History of Soundproofing
The first sounds recorded by the human race were captured on the phonautograph, a device invented by Édouard-Léon Scott de Martinville in 1857. This device worked by transcribing sound waves into a line drawn on paper or glass. The earliest sound recording using the phonautograph was the French folk song "Au Clair de la Lune." That recording, captured in 1860, still exists today. Since then, the world has exploded with sound, so much so that we now seek to quiet it back down.
Soundproofing originated in the 1890s with a man named Wallace Clement Sabine. Sabine, a physicist at Harvard University, stepped into this world when he was asked to figure out a way to improve the acoustics inside the main lecture hall in Harvard’s Fogg Art Museum. He started out by measuring reverberation time; he is the first person we know to have done this. Finding the reverb time to be 5.5 seconds, he began experimenting with different seat cushions, then with sound absorbing materials. Later, using what he had learned, he designed Boston Symphony Hall. It opened in 1900, distinguished as the first building to be designed with scientifically formulated architectural acoustics.
Over the course of the remainder of the 1900s, the world rapidly got louder. By the second half of the century, people were noticing the toll that noise can take, both physiologically and psychologically. The ‘60s and ‘70s were the decades of louder-than-ever-before rock concerts and subsequent hearing loss. In 1978, the U.S. Environmental Protection Agency (EPA) Office of Noise Abatement and Control estimated that around 20 million Americans were exposed to enough daily environmental noise to sustain permanent hearing loss. Also, in 1981, a little more than nine million Americans experienced occupational noise exposure at levels above 85 decibels, and by 1990, that number had risen to 30 million. Eight hours or more at noise levels above 85 decibels can be potentially dangerous to both your eardrum and middle ear.
To combat the noise pollution, both out in public, in factories and in the recording studio, lawmakers and engineers sought ways to neutralize it. In 1972, for example Congress passed the Noise Control Act, meant to establish noise emission standards in the interest of public health. It was also during the 1970s that the United States and other industrialized countries made it common practice to build noise barriers alongside highways. This was not for drivers, but rather as a source of respite for those that live near the highways and would otherwise experience unpleasant roadway noise. One of the first noise barriers to go up was built in Arlington, Virginia, along Interstate 66, while perhaps the earliest scientifically crafted noise barrier went up in 1970 in Los Altos, California. Since then, the Federal Highway Administration (FHWA) and the State Highway Administration (SHA) have agreed that it is the responsibility of the states to adopt their own highway traffic noise abatement policies.
As the years have gone by, soundproofing and noise control have only become more important. Engineers have met this need with more advanced technology, while standards organizations have created multifaceted recommendations for optimum health and safety.
Benefits of Soundproofing
Our world is quite a loud one, and that can take a toll on both the body and the mind. For example, even though noise only stays in the air for a short time, its effects are cumulative in terms of temporary or permanent hearing loss. It can also result in stress, sleep loss, reduced concentration, reduced productivity and overall reduced peace of mind. Soundproofing equipment helps save us from all of that grief. In addition, soundproofing improves the sound quality of recordings. Another great thing about soundproofing equipment is that it is incredibly diverse and adaptable.
How Soundproofing Works
Soundproofing materials work by absorbing sound, dampening sound vibrations, by blocking them at the source, or via a combination of all three.
- Sound Absorption
- Achieved with the use of soft, porous, open-celled foams such as polyurethane foam, which trap sound waves within the foam's labyrinth of non-reflective cells. The higher the ratio of sound barrier surface area to open space, the greater the sound absorption; for this reason, anechoic chamber manufacturers line walls, ceilings and even floors with corrugated foam wedges or panels with pyramid or egg-crate shaped surfaces, which absorb far more sound than flat foam or other acoustic panels.
- Vibration Dampening
- Reduces the amount of vibration energy transmitted between surfaces constructed of rigid materials, which typically transmit vibrations at multiple frequencies. Product testing rooms and acoustical research centers, for example, use vibration dampening to create absolutely minimal noise pollution. Usually this dampening comes in the form of anechoic chambers, or noise control rooms, lined completely with acoustic foam panels, acoustic drywall and acoustical ceilings. These rooms absorb almost all the sound waves produced by a piece of equipment or machinery.
- Sound Barrier Creation
- Sound barriers are literal barriers that block the noise source and reduce its effects. Sound barriers usually come in the form of walls of high density material. Most often, you can find them along a road or highway, muffling the sound of cars. However, they’re also often used as firewall treatments, bulkheads, pipe wraps and cab floors.
Soundproofing Design and Customization
When designing soundproofing equipment, manufacturers start out with an important question: Is this equipment meant to improve the sound within a room, or is meant to prevent sound from leaking out of the room? This helps them know what type of soundproofing equipment will best serve them. For example, anechoic chambers work extremely well for improving sound quality within a room, but blocking leaking sounds is usually not their primary intention.
To make their soundproofing pieces, manufacturers use materials that are specifically designed to absorb sound. Typical materials for this include rock fiber wool and porous surfaces, like urethane open cell foam. Rock wool fiber works by completely absorbing the sound and insulating, while porous surfaces are partially penetrated by sound waves, which they then trap inside them. Wall panels and baffles can also be made from perforated metal.
Soundproofing manufacturers will customize your equipment by making it match your aesthetic. For example, it’s quite common to cover acoustic panels in fabric that blend in existing building decor. They will also customize them in size (sq feet), scope and thickness.
Types of Soundproofing
- Active Noise Control (ANC)
- Or active noise reduction (ANR) is a noise reduction technique in which the addition of a carefully designed second sound cancels out the first. This second sound is usually some sort of low-frequency noise. You can find this technology in headphones, speakers and microphones.
- Acoustic Flooring
- Important for reducing noise emission caused by factory noises, instruments, and walking or operating equipment on a cavernous floor. Carpet and fibrous materials provide a significant level of floor soundproofing for some applications, although tiled or uncarpeted floors may be effectively soundproofed by other means. Acoustic flooring contains floor sound insulation and vibration shock absorbing materials layered on top with thin layers of acoustic foam and porous mineral boards.
- Soundproofing System
- To avoid damage to employees, products and equipment, those facilities concerned with excessive equipment noise use soundproofing products such as acoustic flooring to absorb floor vibrations. Soundproofing systems provide overall sound protection to a large space or room. Acoustical ceilings, acoustic baffles, acoustic foam and acoustic panels are common elements of sound proofing systems, as they have extensive coverage to large surface areas. Their sound wave absorbent materials reduce the reverberations within any space. Performance and music venues typically use soundproofing systems that feature acoustic foam as sound insulation on acoustic wall panels, and acoustical ceilings to prevent noise pollution or echoes that would distort and dilute the main audio.
- Acoustical Ceiling
- A ceiling design that consists of a suspended ceiling grid and high sound absorption lay-in acoustical panels or tiles. It can be used to control the quality of sound effectively in a specific space.
- Acoustic Baffle
- An acoustic material designed to serve as a substitute or complement to acoustical ceilings. To that end, they are hung vertically from a ceiling structure. Acoustical baffles are made up of one or two cores of dimensionally stable medium density glass fiber.
- Acoustic Foam
- Reduces noise and provides insulation by first permitting sound energy to enter its material, then not allowing it to leave. Inside the foam, sound dissipates before it can reach the other side. Acoustic foam is used to line sound-reflective surfaces, including those found in gyms, recording studios, clubs, function halls and churches.
- Acoustic Panel
- A sheet made of sound absorbent material that you can fasten to walls in order to absorb unwanted noise. It is made up of three main parts: the frame, the sound absorbent internal material and the outer covering. Acoustic panels act as excellent insulation from outside noise, and are found on the walls in all sorts of places, from coffee shops to water treatment plants.
- Acoustic Curtain
- Heavy drapes or linen panels made from custom designed materials that block noise from moving in between spaces. In an industrial setting, you can absorb the sound of equipment by surrounding it with acoustic curtains.
- Anechoic Chamber
- A specialized type of soundproofing solution that provides dead space. Anechoic chambers are popular solutions for recording studios, acoustical research centers or equipment testing procedures.
- Sound Isolation Room
- Also known as audiometric booths, are available to audiologists, doctors, hearing aid specialists and hearing clinics for hearing testing and to gather more research on the way in which sound travels and works.
- Locally Applied Soundproofing
- Mufflers, grommets, shocks and vibration isolators are examples of soundproofing applied locally to equipment. Computers contain soundproofing materials, and computer workstations in offices are often housed in soundproof or semi-soundproof rooms.
- Acoustical Blankets
- Consist of polyvinyl chloride outer shells and acoustical batting. Acoustical blankets can be hung from vertical uprights or attached to a frame, enclosing a piece of equipment to absorb and stop noise.
- Acoustical Enclosures
- Used when sound must be prevented from spreading from one area to another. Acoustical enclosures include recording booths, industrial enclosures of all kinds, highway walls and noise barrier walls.
- Acoustic Flooring
- Layers of sound-absorbent material underneath flooring material that reduces sound heard between floors in multi-level buildings.
- Barriers
- Provide a high density layer used to separate or prevent noise from entering a certain area or leaving a contained area. Common uses for barriers are bulkheads, firewall treatments, cab floors and pipe wraps.
- Cloud Panels
- Similar to acoustical baffles but are hung in a horizontal position from the ceiling or roof structure.
- Damping Materials
- Aid in the control of vibration and structure borne noise often through friction or time. This method is common with sheet metal panels, cab enclosure panels, boat hulls and deck plates and HVAC ductwork.
- Diffusers
- Scatter a sound wave from a surface. Sound direction is changed so listeners may experience sound coming from different directions at equal levels.
- Intake Silencers
- Decrease the noise and destructive low frequency pulsations at blower inlets.
- Isolators
- Can reduce vibration by having greater attenuation in one direction than the other and are often found installed under some defined load factor between two surfaces, such as generator pads.
- Modular Acoustical Panels
- Easy-to-use portable panel products, such as partitions, wall-mounted panels, baffles and privacy screens.
- Noise Pollution
- Refers to any unwanted and unpleasant sound. Noise reduction strives to diminish the amount of noise pollution in a given area by breaking, blocking, absorbing or isolating unwanted infiltrating sound waves.
- Reflectors
- Used to regulate the amount of sound that is reflected off a surface. Reflectors are often used in acoustically sensitive settings.
- Silencers
- Reduce the level of sound through either absorptive, reactive or a combination of mechanisms.
- Sound Absorbers
- Noise control materials and are directly related to the amount of surface area available to be treated. Sound absorbers are frequently found in machine enclosures, housings, industrial environments and medical, marine and transportation applications.
- Sound Barriers
- Use walls of high density material to reduce roadway noise.
- Sound Insulation
- Or acoustic insulation absorbs the frequencies transmitted by sound waves and prevents unwanted noise and vibration.
- Sound Proofing
- Refers to the methods used to reduce the intensity of sound.
- Soundproofing Materials
- Used to control or reduce the amount of noise in a given environment by blocking the sound from entering or leaving the space.
Soundproofing Applications
Noise can be either airborne through the air including voices and music and traffic sounds, or it can be structural or impact noise sourced by machinery vibrations, footsteps or the sounds of building systems such as plumbing or heating which pass through the floors and walls. These sounds can prove a disrupting and unpleasant environment in which to live or work. Furthermore, excessive equipment noise not only causes distractions and poor communication in the workplace, but in heavy manufacturing settings, it may cause permanent auditory damage to workers as well. Soundproofing takes care of all of this.
Soundproofing equipment and components are useful in a wide range of settings, and they serve important applications from industrial noise control to hearing protection. For example, medical hearing facilities and product testing facilities, such as computer testing chambers, require soundproof chambers to measure decibel levels given off and affected by products. They are also important in sound mixing studios, performance halls and theaters. Soundproofing is not only required for testing chambers, studios and noisy facilities, but also for smaller equipment such as computers or domestic appliances, and for consumer machines such as cars or jet skis.
Safety and Compliance Standards for Soundproofing
Federal government regulations stipulate maximum noise levels in work environments, schools, offices, airports and other public buildings, often requiring these facilities to install a certain amount of soundproofing in order to remain functional and safe. One governmental agency that puts off sound emission standards is the EPA. The Clean Air Act 201.7641 focuses on noise abatement. If your facility falls under this umbrella, you need to make sure that the soundproofing system meets any and all federal requirements. If you have workers, then those workplace standards put out by the Occupational Safety and Health Administration OSHA are also important to consider.
In addition, independent organizations put out standard recommendations for optimum system safety and performance. ISO 91.120.20, for instance, published by the International Standards Organization (ISO), outlines sound insulation standards for indoor acoustics. ISO standards are used widely outside the USA, while within the USA, it’s more common to follow American-based ASTM International standards. ASTM uses STC (sound transmission class) ratings. These ratings rate how well any given piece of soundproofing technology reduces noise.
How to Choose the Right Soundproofing Manufacturer
Soundproofing is a profitable industry, and so, you will find that there are a lot of manufacturers and suppliers out there vying for your business. So, how to discern the good ones from the duds? For starters, we recommend you use a directory, like this one. Directories do the hard lifting for you by sorting through the riff raff and presenting you with companies you can trust. Looks like you’ve already completed the first step! So, what’s next? Scroll up near the top of this page and find the list of said companies that we’ve compiled. Browse their websites and get a feel for what each of them offer. Then, pick three or four in whom you have the most interest. Prepare your specifications, requirements and questions, and then reach out to each of them. Compare and contrast their responses, paying special attention to their production lead times, delivery policies, prices and customer service. Never forget that customer service is key—Without a company that is willing to work with you to get your product just right, it doesn’t matter how much money you save in the short term! So, go for the company that will treat you the best, while delivering the best product.
Soundproofing Terms
- A-Weighting
- The filtering system in a sound meter that allows the meter to disregard lower frequency.
- Absorption Coefficient
- The ratio of the sound absorbed to the sound incident on the material or device.
- Acoustical Analysis
- A determination of the level of reverberation or reflected sound in the space for which the building materials are a factor. Acoustical analyses also determine how much acoustical absorption is needed to reduce reverberation and unwanted noise.
- Acoustical Material
- The material used to change a sound field by absorbing, damping or blocking acoustical energy.
- Acoustics
- The science of sound, which includes its creation, transmission and effects.
- Airborne Noise
- The uninterrupted transmission of noise into the atmosphere. Airborne noise can be controlled by absorption or by being blocked.
- Ambient Noise
- The sounds within a given environment from many different sources.
- Anechoic Room
- A test chamber lined with absorbent acoustical material used to eliminate sound reflections and to determine the sound radiation characteristics of equipment.
- Bel
- A unit of measurement referring to sound intensity. One bel equals 10 decibels.
- Damping
- The process of dissipating mechanical vibratory energy into heat. Damping materials are used to apply to vibrating surfaces in order to reduce the noise radiating from that surface.
- Decay Rate
- The rate at which sound will fade when the noise source is removed, expressed in dB/sec.
- Decibel (dB)
- A unit of measurement referring to sound intensity that is equal to one tenth of a Bel.
- Dissipative Silencer
- A device inserted into air ducts or openings that reduces the noise transmitted through the ducts or openings. Noise reduction is accomplished by using internal sound absorbing materials.
- Flanking
- The pathway along which sound travels around the perimeter or through holes within partitions or barriers erected to reduce the sound isolation between areas. Examples of flanking paths include ductwork, piping, back-to-back electrical boxes within partitions, window mullions, etc.
- Free Field
- Sound from an outdoor source where no obstructions exist.
- Hearing Threshold (HTL Level)
- Amount in decibels that a specified signal can exceed to cause damage to the ears of a listener.
- Hertz (Hz)
- Sound frequency expressed by cycles per second.
- Insertion Loss
- The reduction of sound power levels reached by inserting a muffler or silencer in an acoustic transmission system.
- Live End/Dead End
- An acoustical treatment plan for enclosed areas in which one end is highly absorbent while the other is reflective and diffusive.
- Loudness
- The strength of the physical resonance of a sound to sound pressure and intensity, as experienced by a listener.
- Noise
- A term referring to a sound of any kind, usually in reference to unintelligible or unwanted sound.
- Noise Criteria (NC)
- Sometimes referred to as "dBA levels," it is used to assess listening conditions at ear level by gauging sound levels at loudest locations in a room.
- Octave Band (OB)
- A range of frequencies where the highest frequency of the band is double the lowest frefquency of the band.
- Radiation
- The process in which structure-borne vibrations are converted into airborne sound.
- Reverberation
- Sound waves that continue to bounce off surfaces after the source ends, until the sound waves lose energy and eventually die out.
- Reverberation Room
- A test chamber designed so that the reverberant sound field within the room has an intensity that should be the same in every direction and at every point. It is often used to measure transmission loss and sound absorption.
- Sabin
- The unit of measure used for sound absorption consisting of the number of square feet of sound absorbing material multiplied by the material absorption coefficient.
- Septum
- A thin layer of material sandwiched between two layers of absorptive material that prevents sound waves from passing through the absorptive material.
- Sound
- Pressure waves traveling through the air or in other elastic materials.
- Sound Absorption
- The acoustical process in which sound energy is dispelled as heat rather than reflected back to the environment as sound.
- Sound Level Meter
- An instrument used to measure sound pressure levels. Type 1 are precision instruments, whereas Type 2 are general purpose instruments.
- Sound Power Level (Lw)
- A measure of the total airborne acoustic power created by any noise source; it is expressed on a decibel scale referenced to a usual standard of 10-12 watts.
- Sound Pressure Level (Lp)
- A measure of air pressure changes caused by a sound wave and expressed on a decibel scale referenced to 20µPa.
- Soundproofing
- Creating an area insulated against noise.
- Structure Borne Noise
- The transmission of energy from vibrating structures or solids into noise.
- Vibrations
- Like those with structure borne noise, they are the wavering of a boundary that defines the motion of a mechanical system and can be reduced by isolators or damping.
- Volume
- Cubic area of a space calculated by the length x width x height of the space. Volume influences reverberation time.
- Wavelength
- Wavelike compressions and rarefaction produced by sound passing through air. Sound waves vary with frequency.