Sound Waves
Have you ever wondered how noise-canceling Headphones works,
or why and how the sky of the Earth during mid-day is blue but orange red
during dawn and dusk?Today I will be writing about everything I know about sound and light waves.
What is a wave?
A wave is a disturbance that transfers energy through a
medium of interacting particles. This oscillating pattern carries energy from
place to place without moving matter itself. There are many kind of waves-
sound waves, light waves, electromagnet waves.
The same principle applies to small ripples in a pond and to
devastating tsunamis.
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| Sound wave moves in pattern similar to ripple |
Noise-Cancelling Headphones
Unlike solid objects, waves- which move energy, can actually
move through each other. There are two important types of results when two waves
move pass each other. The first one is if two waves move in the same direction
and share the same frequency, the result will be additive- a new wave that
combines the amplitude of the first two, still moving in one direction, at the
original frequency.
But if the waves' peaks line up, the combination will result
in a new, higher wave.
On the other hand, the first wave’s peaks line up with the
other’s, the two wave patterns will cancel each other out. Sounds strange
right? There had been two wave patterns, but there will now be none. This is called destructive interference.
So now do you get a brief idea of how a noise-cancelling
headphone works? I used to think that what it does is just to cover our ear
completely and hence there will be no sound travelling into our ears. And turns
out I was very wrong. The headphone's active noise control systems work by
generating a sound wave that is the mirror image of the offending sound wave.
This wave has the same frequency and direction but opposite crests and valleys
and is out of phase with the first sound wave. The result, is minimum sound
blasting into your ear.
An amazing and clever idea right? Active noise control
is usually used in such application as airplane cabin, air conditioning duct,
and wore by pilots, not only to cancel deafening engine noise, but also allow
pilots to communicate. Can you think of other product that applies the active
noise system?
Next week I will be writing about light waves, a more
complicated type of wave, but I will try my best to explain how it works and
why is it useful to us.
Thanks for reading
