Passive Noise Cancellation

This is a fairly crude method of trying to block out noise. It is similar to you clamping your hands on your ears and trying not to hear anything. Basically, what it means is to clamp your ears with some sort of an insulating material that does not carry sound or muffles it.

A good example of passive noise cancellation would be a pair of headphones that completely cover your ears and fit quite tightly around them. These headphones should ideally have a large ear cup that is filled with sound absorbing material. What these sound absorbing materials do is that when the sound vibrations from the air reach them, they act a little stubborn and don’t move as much as the sound molecules move in the air. This dampens the frequency of the sound and as the wave travels through layers of sound absorbent material, it’s blocked right then and there.

They would then block out most of the high frequency noise, and unfortunately, this is where their Achilles heel lies. No matter how good they are, low frequency sounds will always creep in some how and would then not give you the complete silence you might’ve hoped for.

This called for a fair bit of research and the scientists then came up with something termed as Active Noise Cancellation.

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