Since the advent of urbanization humanity has been experiencing a substantial increase in the level of noise pollution. Scientific data states that the average hearing noise level is currently at 98 decibels(dB) , this is significantly higher to the WHO standard of 50 dB for residential areas. Noise cancellation is an expensive yet effective way of catering to this issue .
What is Noise cancellation, and where is it used?
In simple terms, noise cancellation is the process of suppressing noise or unwanted ambient sounds using soundproofing materials or Active noise control (More on that later …)
This technology is developed to protect people from an orchestra of displeasing sounds generally. It is also widely used in industries and research labs as safety hearing equipment for acoustically hostile environments.
The history of Noise cancellation …
It all started in 1978 when Amar Bose (former MIT professor & electrical engineer) was travelling from Boston to Zurich on an aircraft. On this fateful flight, he successfully demonstrated that “Frustration is the mother of invention”. He was extremely annoyed by the fact that the engine noise drowned his in-flight music experience. So he grabbed a napkin and tried to design a concept that could negate this effect. It was those designs and calculations he made several thousand feet over the Atlantic Ocean that gave rise to the BOSE audio as we know it today!
We also need to note that noise cancellation was experimented with earlier, but Amar Bose truly commercialized it.
The types of noise cancellation :
Several decades down the line, we have 2 types of noise cancellation called Active and Passive noise cancellation. Let’s get a comprehensive idea of what it means.
- Active noise cancellation “Eliminates sound ”- This happens by utilizing a phenomenon called Destructive interference. This is otherwise just called “Noise cancellation.”
- Passive noise cancellation “Obstructs sound ”- This happens by using materials or designs that tend to muffle external noise. This is otherwise called “Noise isolation.”
In reality, it's comical to see a substantial proportion of the headphones being marketed as “Noise-cancelling headphones” when the real effect is actually just “Noise isolation”. These are two very different parameters used interchangeably for smart marketing reasons.
So if you are looking to experience the real effect of noise cancellation, make sure to get headphones that support “Active Noise cancellation or ANC”. The easiest way of finding these headphones are by their exorbitant prices, which undoubtedly would leave a lasting hole in your pocket!
Working of Active Noise Cancellation headphones :
So now let's come to the main part where we try to understand what really makes these headphones extremely expensive in the first place.
Firstly we need to acknowledge that these devices use very sophisticated materials and circuitry to achieve a convincing level of noise cancellation. But to make our lives easier, I'll try to explain only the fundamental phenomena that these headphones are trying to emulate.
So now we attempt to understand what destructive interference is. In simple terms, it’s a phenomenon that occurs when two sound waves cancel each other out when they travel with similar magnitude and frequency in opposite directions.
So when this phenomenon has to be emulated practically, we need to have a device that detects external noise and another device that creates and transmits an opposing signal to neutralize it.
Hence, in active noise cancellation headphones, we have an array of microphones on their surface. These microphones constantly detect external ambient noise and signal the headset to generate a similar sound but “Inverted in orientation to the original noise. We have a large array of microphones because it really aids in detecting ambient noise from different frequencies. This results in improving the effectiveness of noise cancellation.
The neutralization of noise is generally taken care of by an active filtering system, a complex electronic circuitry built into headphones.
After all this process, the external noise is completely neutralized before it could reach our ear. We also need to realize that the active filtering system is quietly bulky and contributes significantly to the net weight of the headphones (This is why most Active noise cancellation headphones though being expensive, are made out of high-quality plastic and not metal)
The entire process of active noise cancellation is very effective when you experience single frequencies sounds like aircraft engine sounds or car horns. In other cases, some portion of the noise, which is lucky enough, still manages to find its way into your ear.
So finally, if you’re willing to spend a hefty amount for Active noise cancellation headphones, convince yourself that you’re spending only 30 % on the sound quality and 70 % for the Engineering behind it!