Active Noise Cancellation
What is it? How does it work?
Sometimes, a little bit of silence is all we want. Whether you are walking down the street, being at the train station or in an airplane, it could be hectic and loud especially at peak hours. Or maybe just to listen to good music or ASMR video, aside from our desire for peace and tranquility, we also need to preserve our hearing from loud noises that could harm our ear. That is where active noise cancellation technology will be handy.
Nowadays, this term is regularly being used in our daily lives. We usually find this term used in audio devices such as earphones and headphones. But what is it actually? It is technology to cancel unwanted noise from our hearing. How does it work? It does not cancel out noise by simply blocking it. Instead, there will be microphones at an audio device that detects sound from surrounding and produce its own sound wave to cancel out the existing sound. This will result in less noise and more saturated sound.
Back in the 1950s, Lawrence Fogel invented and patented the technology which were initially used in the aviation industry to make the pilots of helicopters and airplanes feel quieter. In today’s world, this technology is massively used for consumer-centric audio devices such as headphones.
How do active noise cancelling headphones work?
Headphones will have microphones that can pick up the ambient sound. Then, it will analyze the sound wave and create the opposite sound wave resulting in destructive interference. Imagine ocean waves: The ripple pattern produces crest and trough, which is the high part and low part. If the waves were to combine at the positive height of crest with negative depth of trough, it will cancel out each other and result in a flat sea. Or if you prefer a simpler example, the sum of +1 and -1 is 0. Basically that is how active noise-cancelling headphones work. Adding crest to trough and trough to crest, but it is sound wave instead of seawater.
But, active noise cancellation is far from perfect. It does not completely block out ambient noise. It does not create silence, it merely reduces noise. Apparently, low frequency hum works the best. Loud noise from cars by the road become quieter noise from cars by the road. Loud airplane engine roar becomes quieter airplane engine roar. At human vocal range, which is higher frequencies than the ambient, headphones have very tiny effects. Therefore, wearing headphone in public transport in hope to block out cries of the baby three seats behind you will not do you any help.
Is there any side effect?
There are some cases where users of active noise-cancellation headphones reported that they experience dizziness and disorientation while suing the headphones. There is a interview conducted by Wall Street Journal, explained by New York ear, nose, and throat doctor Sarah Stackpole. She said that extremely low-frequency vibrations produced by noise cancelling technology may be transmitted, that stimulate balance receptor connector to our ear’s stereocilia, also known as hearing hair cells. Then, these receptors falsely communicate with our brain that our head is moving, despite being completely still. These mixed messages trick the brain into thinking it is experiencing motion, thus dizziness. One solution to overcome this is to decrease the intensity of active noise cancellation.
Alternative, other than ANC?
If you somehow do not want to use ANC, there is other option to cancel out noises which is passive noise cancellation method. The function is still the same; to reduce noise but it is different from ANC. Passive noise cancellation blocks out sound wave from the environment by using the materials they are made of. The best material for passive noise cancellation is the one that is soft, light, fluffy or porous, which enables them to absorb echo better.
Have you seen a construction worker operate the hammer jack drill while using “headphones?”. It is actually an ear muffler, design to protect their hearing since they work in noisy environment. Or maybe you have been to jamming studios where the walls are made of soft and porous materials and kept you wander, ”What is that?”. It is actually acoustic panel to dampen the noise during jamming sessions, so that they can hear their music clearly. These are some of the usage of passive noise cancellation. In addition, for cheaper headphones that does not have ANC, they will at least have passive noise cancellation technology. These headphones will have a pair of large and thick cup to place the ears inside it. Therefore ambient noise will be reduced.
Noise cancellation technology, whether active or passive, is designed to protect our hearing from getting damaged. There are many usages of the technology that we can apply in a variety of fields. In today’s world, noise pollution is everywhere. We must make sure that we will not be negatively affected by it.
(Pardiwala, 2019)Pardiwala, A. (2019). What Are Noise Cancelling Headphones and How Do They Work? Retrieved November 16, 2020, from https://gadgets.ndtv.com/audio/guide/what-are-noise-cancelling-headphones-and-how-do-they-work-2035865
Written by Muhammad Syahid
Posted on November 17, 2020