Soundproofing

To avoid damage to employees, products and equipment, facilities where excessive equipment noise is a concern use soundproofing products such as acoustic flooring to absorb floor vibrations or acoustic curtains to surround equipment, absorbing their sound. Acoustical ceilings, acoustic baffles, acoustic foam and acoustic panels are also common elements of sound proofing systems as they provide large surface areas of sound wave absorbent materials to reduce the reverberations within a space. Noise reduction and sound insulation have become important elements of construction and building layout as unwanted noise can not only be physically harmful and painful, resulting in hearing loss, stress and sleep loss; it can also decrease concentration, productivity, and peace of mind. Noise pollution from heavy traffic is a major concern in some areas, and sound barriers are often erected as a response. Some specialized applications such as recording studios, acoustical research centers or equipment testing procedures require customized soundproofing solutions, and anechoic chambers, which provide essentially dead space, are one example of this.

Noise can be either airborne through the air including voices and music and traffic sounds, or it can be structural or impact noise caused 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 audio damage to workers as well. Even though noise only stays in the air for a short time, its effects are cumulative in terms of temporary or permanent hearing loss and therefore soundproofing is a worthwhile investment for many applications. Soundproofing materials work by absorbing sound, dampening vibrations, or as sound barriers; or as a combination of the three processes. Sound absorption is 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. Product testing rooms and acoustical research centers requiring absolutely minimal noise pollution build 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.

Depending on the desired results, noise reduction installation may be as simple as installing several acoustic panels or acoustic baffles on the surface of a wall, or it may be as complex as building an entire soundproof anechoic chamber. 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. Other common uses of sound proofing materials include in sound mixing studios, performance halls and theaters which use acoustic foam as sound insulation on acoustic wall panels and acoustical ceilings in order to prevent noise pollution or echoes which distort and dilute the main audio. While wall panels and sound insulation absorb airborne sound waves, acoustic flooring and vibration dampening materials reduce the amount of vibration energy transmitted between surfaces constructed of rigid materials, which typically transmit vibrations at multiple frequencies. Acoustic flooring is also important in other types of industries for reducing noise pollution caused by 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 insulation and vibration shock absorbing materials layered on top with thin layers of acoustic foam and porous mineral boards.

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. 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. Sound isolation rooms, 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. 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.

Images Provided by Eckel Noise Control Technologies

Soundproofing Types

• Acoustic baffles are constructed of one or two cores of dimensionally stable medium density glass fiber and suspended vertically from a ceiling structure. Acoustical baffles are designed for areas where standard acoustical ceilings are not feasible or as an additional acoustical treatment in existing spaces.
  
• Acoustical blankets consist of polyvinylchloride 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 ceilings consist of a suspended ceiling grid and high sound absorption lay-in acoustical panels or tiles and provide a lightweight and attractive ceiling system. Acoustical ceilings, which are quickly installed, can be used to control the quality of sound effectively in a specific space.
  
• Acoustic curtains are heavy duty drapes or linen panels made of specially designed materials that prevent noise from moving between spaces.
• Acoustical enclosures are 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 foams are used to line sound-reflective surfaces. They reduce noise by allowing the sound energy to penetrate into the material and be dissipated by its cellular or fibrous nature prior to reaching the reflective surface.
• Acoustic flooring are layers of sound-absorbent material underneath flooring material that reduces sound heard between floors in multi-level buildings.
• Acoustic panels are fastened to walls in order to absorb unwanted noise.
• 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.
  
• Clouds are 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 are 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 are 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 are 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 a 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 are used to control or reduce the amount of noise in a given environment by blocking the sound from entering or leaving the space.

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.