Noise control is an active or passive means of reducing sound emissions, often incentivised by personal comfort, environmental considerations or legal compliance. Practical and efficient noise control is wholly reliant on an accurate diagnosis of what is causing the noise, which first involves finding the source of noise. Once the source of noise has been found, the focus is reducing the noise at source by engineering means.

The most common noise sources can be divided into aerodynamic (fans, pneumatics, combustion, etc) and mechanical

Machine

A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 (impacts, friction, etc). Effective noise control focuses on reducing the noise from these sources as close to the source as possible. Noise control for aerodynamic sources include quiet air nozzles, pneumatic silencers

Silencer

Silencer may refer to:* Muffler, a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine* Silencer , a DNA sequence capable of binding transcription regulation factors termed repressors...

 and quiet fan technology.

In architectural acoustics

Architectural acoustics

Architectural acoustics is the science of noise control within buildings. The first application of architectural acoustics was in the design of opera houses and then concert halls. More widely, noise suppression is critical in the design of multi-unit dwellings and business premises that generate...

 and environmental acoustics

Noise pollution

Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life...

, noise control refers to the set of practices employed for noise mitigation

Noise mitigation

Noise mitigation is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control...

. Within architectural acoustics these practices include: interior sound reverberation reduction, inter-room noise transfer mitigation and exterior building skin augmentation. “More specific architectural noise control methods include the installation of thicker and/ or double-glazed windows,” acoustical gypsum, ceiling tiles, ceiling panels, carpet and draperies. In the field of environmental sound, common noise control practices include: design of noise barrier

Noise barrier

A noise barrier is an exterior structure designed to protect sensitive land uses from noise pollution...

s, development and enforcement of noise abatement legal codes and urban design.

Types of noise control

There are four basic principles of noise control:

• Sound insulation: prevent the transmission of noise by the introduction of a mass barrier. Common materials have high-density properties such as brick, thick glass, concrete, metal etc.

• Sound absorption: a porous material which acts as a ‘noise sponge’ by converting the sound energy into heat within the material. Common sound absorption materials include decoupled lead-based tiles, open cell foams and fiberglass

• Vibration damping: applicable for large vibrating surfaces. The damping mechanism works by extracting the vibration energy from the thin sheet and dissipating it as heat. A common material is sound deadened steel.

• Vibration isolation
  Vibration isolation
  Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.-Passive isolation:Passive vibration isolation systems consist essentially of a mass, spring and damper ....
  
  : prevents transmission of vibration energy from a source to a receiver by introducing a flexible element or a physical break. Common vibration isolators are springs, rubber mounts, cork etc.

Materials used in architectural acoustics

Acoustical wall and ceiling panels can be constructed of many different materials and finishes. The ideal acoustical panels are those without a face or finish material that interferes with the acoustical infill or substrate. Fabric covered panels are one way to maximize the acoustical absorption. The finish material is used to cover over the acoustical substrate. Mineral fiber board, or Micore, is a commonly used acoustical substrate. Finish materials often consist of fabric, wood or metal. Fabric can be wrapped around substrates to create what is referred to as a "pre-fabricated panel" if laid onto a wall, and require no modifications. Such fabrics are generally acoustically 'transparent, meaning that they do not impede a sound wave. Prefabricated panels are limited to the size of the subas "on-site acoustical wall panels" This is constructed by "framing" the perimeter track into shape, infilling the acoustical substrate and then stretching and tucking the fabric into the perimeter frame system. On-site wall panels can be constructed to work around door frames, baseboard, or any other intrusion. Large panels (generally greater than 50 feet) can be created on walls and ceilings with this method.

See also

• Academic Programs in Acoustics
  Academic Programs in Acoustics
  This page offers a partial list of academic institutions that offer significant exposure to the science of acoustics. Because acoustics is a broad, multi-disciplinary field, many institutions offer acoustics courses through various other departments, such as physics, architecture, or a particular...
  
  
• Acoustic quieting
  Acoustic quieting
  One of the major reasons for the development of acoustic quieting techniques was for making submarines difficult to detect by sonar. This military goal of the mid- and late-twentieth century allowed the technology to be adapted to many industries and products, such as computers , automobiles , and...
  
  
• Architectural acoustics
  Architectural acoustics
  Architectural acoustics is the science of noise control within buildings. The first application of architectural acoustics was in the design of opera houses and then concert halls. More widely, noise suppression is critical in the design of multi-unit dwellings and business premises that generate...
  
  
• Active noise control
  Active noise control
  Active noise control is a method for reducing unwanted sound.- Explanation :...
  
  
• Noise mitigation
  Noise mitigation
  Noise mitigation is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, and occupational noise control...
  
  
• Noise Reduction Coefficient
  Noise Reduction Coefficient
  The noise reduction coefficient is a scalar representation of the amount of sound energy absorbed upon striking a particular surface...
  
  
• Noise, vibration, and harshness
  Noise, Vibration, and Harshness
  Noise, vibration, and harshness , also known as noise and vibration , is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks...
  
  
• Soundproofing
  Soundproofing
  Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using...
  
  
• Sound masking
  Sound masking
  Sound masking is the addition of natural or artificial sound into an environment to cover up unwanted sound by using auditory masking. This is in contrast to the technique of active noise control...
  
  
• Vibration isolation
  Vibration isolation
  Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.-Passive isolation:Passive vibration isolation systems consist essentially of a mass, spring and damper ....
  
  

External links

• Article "How Decoupling Works"
• Case Studies
• Noise control case studies
• Industrial noise control case studies