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The Significance of Noise Cancelling Headphones


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The Significance of Noise Cancelling Headphones

 

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Bose QC35-Active noise cancellation headphone

 

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 generally protect people from an orchestra of displeasing sounds. Apart from this , it is also widely used in industries and research labs as a safety hearing equipment for acoustically hostile environments.

The history of Noise cancellation …

It all started in 1978 when a man called 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 inflight music experience . So he grabbed a napkin & tried to design a concept that could negate this effect . It was those designs & calculations he made several thousand feet over the Atlantic ocean that gave rise to the BOSE audio as we know today !

 

We also need to note that noise cancellation was experimented earlier , but it was Amar Bose who truly commercialized it .

 

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Amar Bose infographic

The types of noise cancellation :

Several decades down the line we have 2 types of noise cancellation called Active & Passive noise cancellation . Let’s get a very broad 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 have the tendency to muffle external noise .This is otherwise called “Noise isolation”

 

In reality it's comical to see a ridiculously large proportion of the headphones being marketed as “Noise cancelling headphones” when the real thing it actually does is 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 on your pocket !

Working of Active Noise Cancellation headphones :

So now lets come to main part where we try to understand as to what really makes these headphones extremely expensive in the first place .

 

Firstly we need to acknowledge the fact 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 make an attempt to understand what destructive interference is . In simple terms it’s a phenomenon which occurs when two sound waves cancel each other out when they travel with similar magnitude and frequency in opposite directions.

 

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The simplified image which shows what happens during destructive interference

 

So when this phenomena 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 the case of active noise cancellation headphones we have an array of microphones on its surface . These microphones constantly detect external ambient noise & signals the headset to generate a sound which is similar but “Inverted in orientation ” to the original noise .The reason why we have a large array of microphones is 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 by an active filtering system which is a complex piece of 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 , but in other cases some portion of the noise which are 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 % for the sound quality & 70 % for the Engineering behind it !

 

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Bose SoundTrue headphones — A classic example of passive noise cancelling headphones

 


Source: The Significance of Noise Cancelling Headphones

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From recent experience, they're good at cancelling out low frequencies. High frequencies, not so good.

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