Noise Cancellation in Headphones — An insight
With the advent of smartphones, tablets and other digital assistants taking mainstream in every day life, delivery of high quality audio for playback and phone calls becomes quintessential in addition to partial or even complete elimination of undesired outside noise also called environment noise or ambient noise. “Noise Cancellation” — a technique that helps in filtering unnecessary background noise from the more essential sounds. This itself encompasses diverse approaches and becomes a bit more complex when applied to headphones.
With OEMs looking for a stellar differentiator for their products, headsets that offer compelling noise-cancellation technology stand ready to easily capitalize. The purpose of this writeup is to shed some light on the basics of noise cancellation and provide insight in to the differences between them.
Noise Cancellation types
Passive Noise Cancellation (PNC) / Noise Isolation
Passive Noise Cancellation (PNC) or Noise Isolation is when the headphones, earphones, earbuds, or in-earphones by itself block outside noise through the use of physical barriers. Imagine we closing our ears with our palms, PNC a.k.a Noise Isolation in headphones achieves the same result by providing a secure seal using the foam pads in the ear cups.
In other words, it is the amount of noise cancellation offered by the physical device when put on head or in ears, ideally how well it works as an ordinary earplug. While a very good design can provide a strong passive cancellation before electronics are applied, PNC is often limited to cancelling frequencies above 1 kHz, more of middle and high frequencies. PNC headphones provide a very good experience when the ear cups completely snuggle the ears without leaving a gap.
Specifically, Circumaural headphones (Over-ear headphones) and On-ear headphones offer passive noise cancellation features, but the one offered by over-ear headphone makes all the difference where it blocks the ambient sound / outside noise giving you great-sounding music / call. In these headphones, Passive noise cancellation accounts for 99% of the noise reduction, which is really good.
Active Noise Cancellation (ANC)
Active noise cancellation (ANC) uses noise cancelling technology to neutralize the ambient noise around us. It works by using additional microphones into the headphones to monitor environmental noise which listen to the outside world (noise) and generate a phase-inverted sound that effectively cancels out ambient noise before it reaches our ears. in simple words, ANC cancels noise by creating equal but opposite noise.
“Active” basically means that headphones have a built-in battery that’s dedicated to powering these dedicated noise-canceling microphones. Improvements in ANC has been significant and battery efficient now that these can be used in true wireless in-ear earphones.
ANC can be achieved with either digital filters or analog filters, and is generally differentiated by the mechanism of cancellation namely feed-forward, feedback or hybrid. A combination of good active and passive cancellation will drastically improve headset performance.
Though there are variety of ANC like feedforward, feedback and hybrid, hybrid ANC, is a best choice for flying, travel etc., as they will filter both low frequency noises — like aircraft — and higher frequencies like human voices, enabling us create a space of our own whatsoever be the environment around us.
Adaptive Active Noise Cancellation (Adaptive ANC)
Adaptive ANC means the levels of noise cancellation is changed automatically on its own without user interference. This is done by detecting changes in the frequency of sound coming at the listener and adapting in real-time for maximum performance. This is more advanced ANC where the level of noise cancelling digitally adapts to the surroundings.
Basically the noise cancellation is high (stronger) when the background noise is loud and vice versa. The higher is the amount of noise cancellation the more aggressively it cleans the sound, negatively impacting its voice quality, so cautious design matters in terms of noise cancellation.
Adjustable Active Noise Cancellation (Adjustable ANC)
In adjustable ANC, the user is allowed to change how much background noise they hear by manually adjusting noise cancellation levels. This feature is particularly useful when user wants to have full control over the noise cancellation feature. A classic example could be using the headset during walking over a busy traffic either for music or on a call etc.
Transparency Mode a.k.a Ambient Fusion
Transparency mode also called ambient fusion, lets you hear what you want to hear around you and interact with the world around you. In this mode, we can clearly hear the announcement of the train arrivals in a station or subway, traffic alerts etc., without taking off the headphones.
“Noise Cancellation” is a blessing in today’s world where most of us work from home, attend schools and colleges online etc., Advances in this technology combined with Artificial Intelligence has been humungous and growing day by day.
Though there are several modes of noise cancellation, in particular active ANC, not only has an effect on sound quality but also on user ears. When ANC is switched on, soundwaves are created which in turn create a pressure against your ears. This is not a painful one, but very similar to a sensation when an airplane takes off. So when using headphones for an extended period of time, users must be aware of noise cancellation and use their best judgement for setting it accordingly.
References
What Is Transparency Mode, and How Does It Work in Headphones? (howtogeek.com)