Soundproofing
Soundproofing is the action taken to reduce the intensity of sound output from a specified source in relation to a subject. The subject can refer to a human, a listening or recording device or a piece of sensitive equipment affected by sound waves and their subsequent vibrations.
There are several different techniques that can be implemented when soundproofing. These include;
- Noise Barriers
- Acoustic Insulators
- Vibration dampers
- Anti noise sound generators
- Interference noise ‘cancellations’
- Increasing the distance between the receiver and the source.
Noise Barriers
These act as ‘deflectors’ bending the sound waves away from the receiver. Typically, noise barriers are seen on major city highways and are used to mitigate the associated traffic noise pollution away from the urban population using the barriers to refract or diffract the sound away where it naturally decays. These barriers are constructed from high density materials like cement or SDS (sound deadening steel) which also absorbs some of the sound.
Acoustic Insulators
Commonly found indoors, acoustic insulators confine noise within the insulated area. Record producers make use of these insulators within their studio rooms to prevent ‘bleed’ from instruments between rooms. Many home theatre systems utilize acoustic insulation techniques to ‘trap’ the sounds within the theatre space with the intention of enhancing the visual / audio experience.
Vibration Damping
Vibration damping is the most common form of treating unwanted mechanical noise. Aside from the obtrusive implications of unwanted noise pollution, vibration can cause irreparable damage to structures due to crack propagation from stress fatigue.
Damping occurs when the oscillatory nature of the vibrations are absorbed by an attached mechanism or material which converts the mechanical energy to heat, and dissipates it accordingly. Vibration dampers are elastic in their physical make up, allowing them to ‘move with the mechanics’ of the overall system and generally speaking, the more elastic a damper is, the more effective it will be at reducing the system’s oscillations. It is desirable in most cases to utilize a damper which has some degree of rigidity to it, so there can often be a trade off between the material’s elasticity and its ability to actually support the system. A series of coil springs or a rubber pad are excellent examples of vibration dampers.
Anti-noise sound generation and interference cancellation
While acoustic insulation, noise barriers and vibration damping are very effective at mitigating sound waves, they only address the problem from the direction of what is known as an unpowered passive solution. The alternative is to fight fire with fire so to speak and approach the problem with an active, powered solution.
Soundproofing using the active method employs the use of anti noise devices which emit a pressure wave at the same amplitude, but exactly out of phase with the sound source, canceling each other out. What this suggests is the natural ‘mountain valley’ cycles of a wave are exactly opposite to each other; (I.E. when the initial source wave is in ‘mountain phase’ the anti noise device will be in its ‘valley phase’.) Once the two waves combine, they rescind each other back to a state of equilibrium. White noise devices, (which are analogous to white light in that they contain all the frequencies of the audio spectrum) perform noise cancellations by emitting a slight static buzz, which sounds very similar to rain, or the ocean, but that actively neutralizes any sound waves operating at the same amplitude.
Increasing the distance between receiver and source
The intensity of sound will diminish proportionately according to the distance of the receiver to the source. In a nutshell, the further you are from a sound, the quieter the sound is. This can be a simple yet effective way of mitigating unwanted noise if you are not inhibited by any lifestyle, legal or environmental factors.
