The Difference between active and passive noise cancellation
Active noise reduction is a concept that most common people do not understand or comprehend well with. Along the course of my work, I have encountered questions like: “What do you do in public gatherings? And I would furtively reply a simple answer such as, “I help in the production of active noise reduction units for huge industries”. Then I would get blank and confused looks because people are not commonly exposed to such terms and conditions. I have noticed that most common folks think of noise reduction as simply placing insulating materials to muffle the noise. But the concept is far from that.
Over the past years however, there has been increasing understanding in the concept of active noise reduction due to the wonderful efforts given by the BOSE in educating people through noise reduction headphones. Nonetheless, active noise cancellation (ANC) or active noise reduction is still confused with its passive counterpart which is sound insulation. This article is targeted to guide people in learning how to differentiate passive cancellation from active noise reduction.
The Fundamentals:
Plainly stated, passive noise reduction is use for deflecting and absorbing sound waves. They are essentially used as a barrier to block external sounds from a person’s hearing. Passive techniques can be done by employing earplugs made of foam, installing foam in interior linings of cars or rooms, and also creating huge and thick barriers that reach 20 foot in height when near traffic areas. The passive noise reduction technique is used solely to absorb unwanted noise and convert it into heat energy or reflect it to a different path.
On the other hand, active noise cancellation operates on the rule of negative interference; which means that a specific wave is produced to cancel out the sound wave of the unwanted noise. To concretely see this idea, let us imaging the waves present in water. When a single stone is dropped in a lake, this will create waves or ripples that rapidly travel around the area. When a second stone is thrown into the pond, it will also create another ripple which will mix with the other stone’s ripple. You will now notice the emergence of an area with no waves produced; although only small in size, the surface created is smooth and flawless. This idea is now likened to what we call “destructive interference” such that a second wave can cancel out the effects of the first wave.
Why Active noise reduction is better than its passive counterpart:
Active noise reduction gives you complete coverage of noise reduction techniques. You will not be bothered by other existing sound waves that escape the passive noise reduction units. Low frequency noises have a higher capacity to penetrate insulating barriers which is why passive types of sound reduction techniques are not effective against it. Another thing is that active noise reduction gadgets have a lower sound threshold which can successfully block out sounds having 1000Hz or lower vibrations. An active noise reduction material is perfect for noise below 300 Hz and can also be applied to other levels depending on the situation.
However, this does not mean that you have to strictly opt for the active noise reduction systems alone. Experts advice that an effective sound reduction system would include all possible sources of sound blockage. Thus, to completely muffle unwanted sounds you must employ both passive and active noise reduction treatments to create a 100% sound proof home.
