Active Noise Reduction and Control

Industrial Noise Pollution

Industrial Noise Pollution is becoming a nuisance and measures have to be taken to reduce it or at least control it. It is hampering the physical and mental health of the workers and is alienating them from society…No I am not exaggerating…this is truth that factory workers are suffering from withdrawal symptoms and it is high time that we start taking the issue seriously.

Active Noise Control or Active Noise Cancellation or Active Noise Reduction

Introducing a nullifying "antinoise" which has the same amplitude but the opposite polarity to the noise that is being controlled, which combines to form a new wave, does active noise control. This process of the combining of two waves is called Interference and this cancels both the sound waves. The process of cancellation is called Phase Cancellation. A proper cancellation scheme has to be prepared. The result of Active Noise Control is a sound wave that is barely audible. Two waves of equal amplitude and identical phase add together to increase whereas two waves of equal amplitude and opposite phase result in cancellation of the sounds.

After the unwanted noise is identified, active noise control can work to generate correct signals that is send to the loudspeakers which start producing anti sound to nullify the original sound. The zone of silence is dependant on the wavelength of both the sounds and the wavelength would depend on the size of source of unwanted sound and the size, number and position of the loudspeakers, which would produce the anti-sound. It is advisable to keep the audio power level of both the sources, i.e. the source of unwanted sound and the source of anti sound, the same. The source of anti-sound or the "transducer " should be kept exactly where the sound needs to be weakened which would be the ear of the listener or listeners. It works better if done in case of a single listener since it requires lower power level.

Contemporary Active Noise Reduction can be achieved by the use of computers. The computer examines and identifies the waveform and the wavelength of the noise and then generates the polarization and reverse waveform so that interference can be achieved. As stated above the wavelength and amplitude of the sound is the same but the polarity is reversed. This whole process creates the desired result of destroying the noise.Active Noise Reduction is different from any other process of noise control method especially soundproofing since in all the other methods power is not in use. Insulation and sound absorbing tiles are mechanical ways of controlling noise.

There are reasons behind using Active Noise Control method when compared to all the other methods because it requires lesser equipments and lesser power. It works very well on lesser frequencies and in case of a single user who is static, it can be handled well but when it is a dynamic user, noise control becomes a challenge. There are different environments where noise needs to be controlled and depending on that application also differs. Repetitive sounds are easier to handle than continuous sounds. In a noise area where the source of noise is singular, active noise control is an easy process and other processes are also effective like the ear mufflers or insulators. In this case the source and the obstructer maintain a physical contact whereas when the sources of noise are multiple and the listeners are multiple or the single listener is kinetic, low frequency sound has to be used which can beu8sed to counter the high frequency noise.Places, where Active Noise Control is used, are aircrafts, car interiors and factories.