Noise Cancellation Headphones mechanism and process

Be relaxed, let them make noise

One man's noise is another man's music, but no matter what is your taste, ambient noise is the enemy. Luckily there is a piece of audio equipment design to enhance your listening experience keeping the ambient noise out and providing you with pure and perfect real beats and sweetness of music

We are talking about one of the common but ultimate equipment, NOISE CANCELLATION HEADPHONES. Treble of the pop song or bass of the jazz song, or even the soothing wave of Sufi songs, every music lover needs a tranquil and serene tone.
Let us take a look at mechanism of this superb equipment.

HISTORY

On a flight to Europe, Amar Bose, the founder of BOSE Corporation, put on a pair of airline supplied headphones, only to find that the roar of the jet engine prevented him from enjoying the audio. He started making calculation right there on the plan if it is possible to use headphones as a noise cancellation headphone a decade later.

WORKING PRINCIPLE

When we talk about wave, most of the people may think about water waves, like we see in pond or ocean. The shallow water wave is an example of transverse wave, which causes a disturbance in a medium perpendicular to a direction of the advancing wave. In the given illustration we can see crest, wavelength, amplitude and though. I will assume all of you must be familiar with these terms.

Sound wave have same characteristics as water waves but they are longitudinal wave created by a mechanical vibration in a medium that produces a series of compression and reflections  in a medium.
For sound wave, amplitude determines the intensity or loudness of the sound of the sound. Frequency determines the intensity or loudness of the sound. Frequency determines the pitch with higher pitch and lower frequencies producing a lower pitch notes. The brain is able to interpret these characteristics of sound, whwn detected by ear, our sense organ.

Noise-canceling headphones come in either active or passive types. Any type of headphone can provide some passive noise reduction,because the materials of the headphones themselves block out some sound waves, especially those at higher frequencies.The best passive noise-canceling headphones, however, are circum-aural types that are specially constructed to maximize noise-filtering properties. That means they are packed with layers of high-density foam or other sound-absorbing material, which makes them heavier than normal headphones. The trade off of all that extra weight is a reduction in noise of about 15 to 20 decibels (dB). But considering jet engines create 75 to 80 dB of noise inside the aircraft cabin, passive models have some serious limitations. That's where active noise-canceling headphones come in.

Active noise-canceling headphones can do everything that passive ones can do their very structure creates a barrier that blocks high-frequency sound waves. They also add an extra level of noise reduction by actively erasing lower-frequency sound waves. They actually create their own sound waves that mimic the incoming noise in every respect except one: the headphone's sound waves are 180 degrees out of phase with the intruding waves.

 Look at the illustration below, you can see how this works.

Notice that the two waves, the one coming from the noise-canceling headphone and the one associated with the ambient noise have the same amplitude and frequency, but their crests and troughs (compression and rarefaction) are arranged so that the crests (compression) of one wave line up with the troughs (rarefaction) of the other wave and vice versa. In essence, the two waves cancel each other out, a phenomenon known as destructive interference. The result: the listener can focus on the sounds he wants to hear.

Function of components

• Microphone - A microphone placed inside the ear cup "listens" to external sounds that cannot be blocked passively.

• Noise-canceling circuitry - Electronics, also placed in the ear cup, sense the input from the microphone and generate a "fingerprint" of the noise, noting the frequency and amplitude of the incoming wave. Then they create a new wave that is 180 degrees out of phase with the waves associated with the noise.

• Speaker - The "anti-sound" created by the noise-canceling circuitry is fed into the headphones' speakers along with the normal audio; the anti-sound erases the noise by destructive interference, but does not affect the desired sound waves in the normal audio.

• Battery - The term "active" refers to the fact that energy must be added to the system to produce the noise-canceling effect. The source of that energy is a rechargeable battery.

That means about 70 percent of ambient noise is effectively blocked, making noise-canceling headphones ideal for airline and train travel, open office environments or any other location with a high level of background noise

Pros of Using Noise-Cancelling Headphone 

 1. Noise-Cancelling Headphones Block Most Sounds

 2. Music Volume Does Not Need to Be High

 3. Lower Music Volumes Provides a Richer Listening Experience

 4. Noise-Canceling Headphones Are Great for Traveling

 5. Noise-Canceling Headphones Are Ideal for Studying

Cons of Using Noise-Cancelling Headphones

  1. Cost of Noise-Canceling Headphones

  2. High Power Usage of Noise-Canceling Headphones

  3. Quality of Sound When Using Noise-Canceling Headphones

  4. Not All Sounds Are Blocked by Noise-Canceling Headphones

  5. Comfort Concerns While Wearing Noise-Canceling Headphones

In spite of these tradeoffs, many people would never go back to normal audio headphones. That's because noise-canceling headphones do more than reduce noise. They also help alleviate fatigue when traveling, which can result from exposure to low-frequency noise for an extended period of time. You can even use noise-canceling headphones if you don't want to listen to another audio source but do want to cancel out background noise. And a little bit of quiet can be music to anyone's ears.