My best friend is a pair of noise-cancelling headphones
They reduce otherwise ear-splitting noises to an almost-pleasant background hum, blocking out the scream of train brakes, the hum of an AC unit, or the roar of a jet engine. I’m wearing noise-cancelling headphones right now, drowning off the dulcet tones of my coworkers’ talks. Let’s look at how noise canceling works in this post.
What are noise-cancelling headphones and how do they work?
Technically, all headphones have some form of passive noise canceling capabilities. If the headphones cover your ears completely, they physically filter out part of the vibrating air that would otherwise reach your eardrums and be interpreted as unwanted noise by your brain. Even anything as basic as putting a cotton ball in your ear counts as passive noise cancellation.
When we talk about noise-cancelling headphones, we’re usually referring to a method called active noise cancellation. Outside of consumer audio, active noise cancellation, abbreviated as ANC, has a variety of uses. However, for the sake of this discussion, let’s concentrate on how active noise cancellation is used in headphones.
Consider what noise is in order to comprehend how active noise cancellation works. The signal that the listener wishes to hear is coming from the sound source through the headphones, and the noise is anything that may interfere with the listener’s ability to hear the signal.
Keep in mind that sound is a pressure wave at its most fundamental level. We’re looking at a depiction of air compression and rarefaction when we look at a waveform. If we played two identical waves at the same time, we’d have the same result as if we just played one, but with a larger amplitude. However, if we moved one of the waves 180 degrees out of phase, we would hear nothing! The peaks and troughs of two similar waves cancel each other out when one signal is played inverted. When two signals totally cancel one other, they are said to be phase canceling, or null. This method is useful in a variety of other audio engineering applications as well.
So, what does this have to do with headphones? Because they have microphones built in, active noise cancelling headphones may theoretically be considered to as headsets. The headphones’ DSP (digital signal processing) chip analyzes the noise, utilizing the manufacturer’s algorithms to anticipate the most accurate possible depiction of the outside noise picked up by the headphones’ mics. The noise is then eliminated from the signal using phase cancellation, which involves the headphones inverting the phase of the noise and adding it to the playback, resulting in less external noise reaching the listener’s ears.
Noise cancellation using active noise cancellation isn’t ideal. For example, when the frequency of unwanted noise rises, it becomes more difficult to analyze. In practice, this means that active noise cancellation works best for eliminating low-frequency, frequently repeated environmental sounds like airplane hum.
Although they may be more comfortable than regular studio headphones, noise-cancelling headphones may not be the ideal choice for music creation. Active noise cancellation, as previously stated, alters the input signal, which is unsuitable for mixing and mastering applications that need thorough listening.
Another drawback of active noise reduction for consumer audio is its cost. The cost of the small microphones, sophisticated DSP processors, and proprietary algorithms is high, especially when compared to passive noise canceling solutions. I would recommend an open-back or semi-open-back set of headphones over circumaural noise-cancelling headphones if you’re already working in a pretty quiet environment or if you’re seeking to utilize them for studio purposes.
Hopefully, you now have a better grasp of how noise-cancelling headphones operate and how they may be used. As the train draws in for your daily commute, it’s time to sit back and enjoy your music instead of the scream of ablative material coming off the brakes.