If you have ever been unlucky enough to get a window seat over an airplane wing, you know quite well that the engine noise can be extremely irritating. We know you wanted the noise to stop, but how could you? You know upping the volume level to full blast will damage your eardrums in the long run, but you had no choice. Well, look no further as noise-canceling technology may just be what you are looking to rid the extraneous noise around you.

How does noise cancellation work? Before we delve into that, let’s see how sound is created and transmitted…

Sound: How it Works?

Sound is created when an object vibrates in a medium (air, liquid or solid). To understand this more clearly, let’s take an example of a person speaking. When a person speaks, the vocal chords inside his throat vibrate. When they move forward, they collide with the air particles in that particular space and moves them further which leads to collision with the next set of particles and so on (this is called compression). When chords move backwards, they create a low-pressure (called rarefaction) region that sucks the particles back towards them and each time includes more particles towards the chain of particles moving to and from that area.

So, a vibrating object sends a wave of vibrations that after reaching our ears, they get interpreted as sound. The reason we don’t hear the same sound from all objects is because the faster it vibrates, the higher the frequency and hence a higher pitch or note. If the object is moving slowly then the frequency is lower, and the pitch is more towards the bass frequencies.

Now each sound has a wave curve that looks something like this:

Note that that the peaks are called crests and the valleys are called as troughs. For instance, if two people stand and scream at the top of their voices it would seem a lot louder than if they were screaming one by one. This is because they are both screaming together, therefore the sound waves they are creating are "in phase". This means that if you were to draw a graph for their sound waves (as above) and super impose them, you will find that their crests and troughs occur at roughly the same time giving rise to a sort of simple addition of sound. This, at least theoretically, is how you hear sound. At this point, it would be more appropriate to mention that sound travels faster in solids than in air and liquids as the molecules are more closely packed in solids and easier and faster to hit.

It would now be a lot easier for you to comprehend the concept behind noise cancellation. There are two kinds of noise cancellation techniques:

1. Passive Noise Cancellation
2. Active Noise Cancellation

 

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