Understanding Active Noise-Cancelling (ANC) Headphones
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The Difference Between Noise-Isolation and Noise-Cancellation
There’s a big difference between ‘noise-isolation’ and ‘noise-cancellation’. The former simply minimizes the amount of external sound that gets into your ear based on the physical design of the earcups. It may also be referred to as ‘passive noise cancellation’. Basically, these headphones or earbuds block out noise by creating a snug fit and good seal between your ear and the outside environment so you can focus more on the desired sound at hand. Over-ear models that fit all the way around your ear have thickly padded cups designed to block out as much outside noise as possible.
On the contrary, active noise-cancellation makes use of a technological method for reducing unwanted sound by adding a second sound specifically designed to cancel the first, thereby eliminating external sound outside your headphones.
Active Noise Cancellation (ANC) – How did it start?
In 1933 in Germany, Paul Lueg, a doctor of philosophy and medicine, realized that he could cancel sounds around a loudspeaker by using phase-advancing waves and inverting polarity to cause interference at specific points in space. A patent application was even submitted. Lueg’s idea was theoretically functional and ground-breaking at that time but there wasn’t any proper equipment to detect, process and generate sound. Thus he could not translate his idea into something that can be used by the general public.Nonetheless, he laid down the foundations of what we know today as Active Noise Control.
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By the 1950s, Dr. Lawrence Jerome Fogel was considered to be the inventor of active noise cancellation when he designed one of the first noise-cancelling headphone systems. He created systems and submitted patents about active noise cancellation specifically for the field of aviation. His designs were to reduce noise for pilots in the cockpit area to help make their communication easier and protect hearing.
Later on, Willard Meeker designed an active noise-control model that was applied to circum-aural earmuffs for advanced hearing protection. Noise-cancelling aviation headsets then became commonly available. A number of airlines provide noise-cancelling headphones in their business and first class cabins.
How does ANC Work?
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ANC makes use of digital signal processing (DSP) technology to actively reduce ambient noise. This works in 4 steps:
- Headphone has an internal microphone that ‘listens’ to the sound around you and detects incoming ambient sound.
- The sound picked up by the microphone is then sent to the noise-cancellation circuitry in the headphone.
- The circuitry inverts the sound and produces an anti-phase (opposite shape) sound wave of equal magnitude.
- This is fed back into your headphones to cancel the ambient noise using destructive interference (original ambient sound and newly added waveform cancel each other out).
Higher-frequency sounds have a shorter wavelength, and cancelling such frequencies would require detecting and counteracting it closer to the listener's eardrum that is either currently technically unfeasible or would require digital algorithms that would complicate the headphone's electronics. Most decent ANC models can handle constant ambient noise like conversation, air conditioning units and jet engines, but sharp changes like someone shouting or a door slamming are difficult to fully eliminate. Thus to prevent higher-frequency noise from reaching the ear, most noise-cancelling headphones depend on sound isolation as well.
OneOdio A10 Headphone (Picture credit: Oardio.sg)
The OneOdio A10 is a wireless noise-cancelling headphone with backup wired connection. Itsnoise reduction effect is -23 to -25 dB, and the listening environment in various scenes is improved by cutting off up to 90% of the harsh low frequencies and ambient noise, suppressing outside noise. The airplane adapter accessory allows you to watch videos on a plane, which would be really useful, since planes have a high level of ambient noise.
Stay Safe!
Regardless of which headphones or in-ear-monitors we use and whether they have ANC capabilities, we should always be careful when we put them on outdoors. This is because they do block out a substantial amount of sound from the surroundings. Thus we need to be extra aware and remove them in situations where we need to hear our surroundings for safety!