Noise control is an active or passive means of reducing sound emissions, often incentivized 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 the noise. Once the source of noise has been found, the focus is on reducing the noise at the source by engineering means.
The most common noise sources can be divided into aerodynamic such as fans, pneumatics, combustion, etc, and mechanical such as 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 includes quiet air nozzles, pneumatic silencers, and quiet fan technology.
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, concrete, metal, etc.
• Sound absorption: a porous material that acts as a ‘noise sponge’ by converting the sound energy into heat within the material. Common sound absorption materials include 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 a sound-deadened steel.
• Vibration isolation: 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.