How Noise Cancellation Works

Noise cancellation technology makes life better. By reducing unwanted background noise and actively reducing ambient disturbances, equipment like noise-cancelling headphones have been proven to help people concentrate and relax more in busy environments; whether travelling on a plane or working in the office or at home.

We’re the UK’s leading hirer of noise-cancelling headphones and we’re passionate about peace and quiet. Allow us to tell you more about the technology behind the noise cancellation and the things to look out for as a headphone user.

Why is Noise a Problem?

Unwanted background noise is a burden on the ears and the brain. Modern travel and working environments are excellent at creating consistent, low frequency background noise which is generated by a range of sources; people chatter, cabin vibrations and engine noise, as well as poor interior acoustic can all contribute to situations where it’s difficult to relax and to produce your optimum working outputs. Research has shown that consistent background noise creates extra workload for the brain[1].

Thanks to audio researchers we now have a better understanding the effects of prolonged exposure to low-level background noise, and the effects it may have on our well-being and productivity. Researchers in the field of noise reduction have identified[2,3,4]

  • Noisy environments greatly increase the likelihood of air passengers experiencing fatigue
  • People who are exposed to ambient noise often find it more difficult to recall information and overcome workloads

More and more people are turning to active noise cancellation technology in the form of noise cancelling headphones to help relax in everyday working spaces including the office, in the library and in busy public spaces such airports and convention spaces.

How Does Noise Cancellation Work?

Noise reduction can be achieved by specialist headphones through either a combination of, or a preferred use of passive and active noise cancellation techniques.

Active Noise Reduction (ANR) or Active Noise Control (ANC) are systems employed by noise-cancelling headphones that we hire at Place Over Ears. These headphones reduce nuisance sounds by the addition of a second negative sound in their audio output, which is specifically designed to cancel stable, low frequency noises in the environment.

Acoustic experts in white lab coats call this process destructive interference. Normally, a phrase containing the word ‘destructive’ wouldn’t be welcome, but it actually refers to the elimination of unwanted noises, a process which could be called anti-noise.

Active noise cancelling headphones rely on a separate power source; hence why these reductive headphones require their own battery. When the headphones are powered, a digital noise processing system actively ‘listens’ to the environmental audio signals. By using a clever algorithm attuned to a range of lower frequency signals, the processing unit within the headphones reproduce an inverted audio signal that to the listeners ears; effectively cancels out the background noise; hence the term noise cancelling. Audio experts suggest that active cancellation improves the headphones’ signal-to-noise ratio

Headphone Performance at Noise Reduction

Headphones that utilise active noise reduction, will often quote their noise-cancelling capabilities in tested environments. For example, Audio Technica’s ATH-ANC9 model (pictured) offers 95% reduction at the lower frequency range of 200hz. However, its important to remember that noise reduction operates at its optimum in a lower range of sound frequencies. When sound frequencies increase, or their patterns become more erratic, noise-cancelling will rely more on their sound insulation to protect your listening experience.

An image of Audio Technica's ATH-ANC9 headphones which incorporate active noise cancellation

Headphones equipped with Active Noise Reduction are still capable of working without their reduction capabilities activated. So, if you run out of battery power you can still listen to your music, but you won’t be able to enjoy the headphone’s ANR capability.

Staying Safe With No Noise

Due to these headphones capability to diminish background noise substantially, for safety, it is important to avoid using active noise cancellation while driving or cycling, or when operating machinery that relies on audible safety warnings and environments that depend on complete aural awareness to maintain a safe environment. As with other types of headphones, noise reduction technology should only be used in accordance with the equipment’s operating instructions. Reduce the noise but stay safe.

Sources

[1] Molesworth, B., Burgess, M. and Kwon, D. (2013), “The use of noise cancelling headphones to improve concurrent task performance in a noisy environment” Applied Acoustics, 74 110-115.

[2] Belojevic, G., Slepcevic, V. and Jakovljevic, B. (2001) cited by Molesworth, B., Burgess, M. and Kwon, D. (2013), “The use of noise cancelling headphones to improve concurrent task performance in a noisy environment” Applied Acoustics, 74 110-115.

[3] Ljung, R., Sorqvist P., Kjellberg A. and Green A. (2010) cited by Molesworth, B., Burgess, M. and Kwon, D. (2013), “The use of noise cancelling headphones to improve concurrent task performance in a noisy environment” Applied Acoustics, 74 110-115.

[4] Ljungberg, J., Neely G. (2007) cited by Molesworth, B., Burgess, M. and Kwon, D. (2013), “The use of noise cancelling headphones to improve concurrent task performance in a noisy environment” Applied Acoustics, 74 110-115.