Active Noise Reduction and Control Technology

Industrial noise pollution is becoming a nuisance, and measures have to be taken to reduce or control it. Its effects are hampering the physical and mental health of the workers and is alienating them from society. It is true that factory workers are suffering from withdrawal symptoms and it is high time that we start taking the issue seriously.

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, is active noise control(ANC). This process of combining the 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 depending on the situation. The result is a sound wave that is barely audible. Two waves of equal amplitude and identical phase add together to increases sound, whereas 2 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 noise.

The zone of silence is dependent on the wavelength of both the sounds and the wavelength would depend on the size of the source of the 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 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 a lower power level.

Contemporary active noise reduction (ANR) 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.

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. This process is different from any other noise control method especially soundproofing since in all the other methods power is not in use. Insulation and sound absorbing tiles are mechanical solutions.

There are reasons behind using these methods when compared to all the others, because it requires lesser equipment and lesser power. It works very well on lower frequencies and in case of a single user who is static, it can be handled well. However, when it is a dynamic user, this becomes a challenge.

There are different environments where noise needs to be controlled and depending on that, the application also differs. Repetitive sounds are easier to handle than continuous sounds. In an area where the source of noise is singular, this 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 be used to counter the high frequency noise. Places, where this technology is used, are aircraft, car interiors, and factories.