It essential to understand the varying features of sound to get a grasp on the way active noise-canceling earbuds work. If you try to imagine how sound looks like, you'd probably imagine a wave-like image.
And that is correct; sound does look like a wave, wobbling up and down. In its very essence, the sound is nothing more than the decompression and compression of various particles in the frequency in which they travel or flow.
Just like in the image above, the air particles vibrating result in pretty minute alterations in air pressure. These slight changes in air pressure are what are known as pressure amplitude. Human ears can pick up, identify the change in air pressure as sound waves.
The loud any particular sound is, the higher it’s wavelength travels, look at the highest point of the sound wave in the image – that is where the sound was the loudest.
Now we can shed some light on the physics behind how noise-canceling headphones eliminate ambient sounds and noises. They do so via a process or method is known as phase and anti-phase. The highest point of a sound wave is the peak, and the lowest point in a sound wave is the trough.
So, when you take two different types of waves and position them one atop the other, matching both the peaks as well as the troughs, the result is identified as an in-phase, which is what happens in a bigger sound wave.
Noise cancellation headphones function by moving a sound wave over the other, minutely mimicking the trough of one sound wave with the highest point of the other sound wave, effectively canceling the noise.
The result is that the waves go out-of-phase, reducing to nothing. Just think of it as trying to add one number and subtracting the same number at the same time. The remainder will be a big 0, which is the very core of the physics surrounding effective noise cancellation technologies.
The answer – very small microphones. Noise elimination headphones come fitted with tiny, externally attached microphones that actively listen to all the ambient sounds and noises, and then process those sounds like a wavelength.
The headphones then achieve noise cancellation by making an exact opposite of the sound surrounding you (anti-phase). They cancel these sounds so that the only sound waves that leak into your ears are the songs you are playing.
However, much of the physics behind noise cancellation is still theoretical. There are still different types of high frequency and inconsistent sound patterns that active noise elimination headphones cannot cancel. The technology we have today is not yet perfect.
While the physics behind the current technology remains the same, there are a handful of companies that do manufacture and design cutting-edge noise eliminating headphones, but they are costly. But it is still important to pick and choose a product that suits your specifications and requirements.