How do Noise-Canceling Headphones Work?

In your search for a new pair of headphones you may have come across some that have active noise cancelling (ANC). But what is it and how does it work?

To understand how to cancel noise, you must first understand sound waves. If you try to visualize sound, you probably picture it in the form of a wave like the one pictured above. Though this 2D illustration will definitely come in handy later, it isn’t entirely an accurate depiction of what sound actually is. At least not until you fully understand what it implies. This is where physics kicks in.

Sound as you hear it is really just the compression and decompression of the particles in the medium in it flows through—for our purposes, we’re talking about air. It may be a little easier to picture sound as a 3D ripple through air. Those moving particles lead to very slight changes in air pressure. We call the measured power of these changes in air pressure amplitude. Your ears and brain detect and decipher those changes in pressure as sound. If you were to chart the amplitude, over time you end up with the wave pictured above. The louder the sound, the more extreme the amplitude.

How your headphones cancel outside noise

Your headphones cancel outside noise by using a trick of physics called “anti-phase.”  If you were to take two identical waves and place them on top of each other matching up the peaks and troughs, the two waves are said to be “in-phase” which results in an even larger wave (louder sound). But what happens if you delay one of the waves by exactly one half wavelength matching up the the troughs with the peaks of the other like in the picture below?

The two waves are then said to be “out of phase” and subtract from one another as the positive pressures of one wave are acting against the negative pressures of the other, and vice versa. Think of it as trying to add one and subtract one. You’re just left with zero. This is the basic physics behind active noise canceling. But how is that used in your headphones?

The microphone array records the noise around you to calculate how to cancel it. Headphones make use of this by way of tiny microphones on the outside of your headphones. They listen to the ambient noise around you, and then the onboard electronics take it from there. The headphones then create sound that is exactly opposite to that sound wave (the anti-phase) to cancel it out so that all you should hear is the music coming from your headphones—and not anything going on outside.

In a word, to cancel the lower-frequency portions of the noise, noise-cancelling headphones use active noise control. They incorporate a microphone that measures ambient sound, generate a waveform that is the exact negative of the ambient sound, and mix it with any audio signal the listener desires.

The two main uses of noise-canceling headphones:

1. Commuter

If you’re a commuter or listen to your music in public, there is no better upgrade you can get than wireless noise canceling headphones. Noise cancellation makes it possible to listen to audio content without raising the volume excessively. It can also help a passenger sleep in a noisy vehicle such as an airliner. In the aviation environment, noise-canceling headphones increase the signal-to-noise ratio significantly more than passive noise attenuating headphones or no headphones, making hearing important information such as safety announcements easier. Noise-canceling headphones can improve listening enough to completely offset the effect of distracting concurrent activity.

 2. As a sleeping aid

Over the last few years, the use of noise-cancellation headphones as sleeping aids has increased. Both active and passive noise-cancellation headphones and earplugs help to achieve better noise isolation from ambient sounds, which is particularly helpful for people suffering from insomnia or other sleeping disorders, for whom sounds such as cars honking and snoring impact their ability to sleep. For that reason, noise-canceling sleep headphones and ear plugs are designed to cater to this segment of patients.

Now that you know how it works and its main uses, why not pick the pair that’s right for you? Our Mu6 Space 2 Noise Canceling Headphones is here for you.