Explanation Needed: What is active noise cancellation? And how does it work?
Image source: Apple
Active noise cancellation is a fascinating feature used in consumer headphones. It's the one feature many consumers like me want when shopping for quality headsets, particularly the over-ear versions. In this new episode of Explanation Needed, we'll delve deep into this audio technology. What exactly is Active Noise Cancellation? And how does it function?
Two companies who pioneered ANC are Bose and Sennheiser. In the present day, the technology is featured in many over-ear wired and wireless headphones, and now made its way to truly wireless earbuds, think Sony WF1000xm3 and AirPods Max. For several decades, the technology itself has been around since the 1970s, to be exact, made explicitly for pilots.
What exactly is active noise cancellation?
In short, It's generally a methodology used to reduce unwanted sound by adding a second sound primarily designed to cancel the first.
So how exactly does it work?
There are two or more microphones on the outer portion of the headphones that seek out environmental noise and quickly creates a mirror image of compressed air or external sound.
I know the answer to the question was a bit vague and short but bear with me. Let's go in-depth so you can better understand the technology. See, to understand how noise is canceled in headphones, you must know the general physics of how sound travels. We always visualize sound traveling in a wave-like pattern. The 2D illustrations that depict how sound travels are inaccurate.
The sound that we hear is just the compression and decompression of flowing air particles. The movement of particles leads to a change in air pressure—the measured power of these changes referred to as being pressure amplitude. The ears and brain detect and translate the differences in air pressure as sound.
OK, so does your headphones cancel external sound?
The headphones use physics to cancel outside noise; call it "anti-phase." Let's breakdown this concept.
Take two identical waves and place them above each other. Matching up the peaks and troughs with multiple waves considered to be in-phase." Forming an enormous wave, or louder sound. If you delay one of the waves by one-half wavelength, two wavelengths are considered to be "out of phase." Subtracting from one another, causing one wave's positive pressure to act against the other's negative pressure. In laymen's terms, this is sound-canceling each other out.
It’s all in the microphones.
So how does the "anti-phase" concept applies to headphones? The tiny microphones outside the headphone listen to the user's ambient noise, and then the internal circuitry takes over. The headphones create the sound opposite to that sound wave ( anti-phase) to cancel it out so that you can hear music from your headphones, minus the external noise.
What’s the caveat to using ANC?
The downside with headphones featuring ANC is when used for an extended period tends to drain battery life. Also, when active noise cancellation is activated, overall sound quality is compromised. A quality pair of headphones often will not succumb to such pitfalls.
