How Does Noise Cancelling Work

By: Tiffany Connors  | 
A woman wearing a bluetooth headset. 
Bluetooth Image Gallery Smaller, stylish headsets can pick up your voice through the vibrations from your jaw. See more pictures of Bluetooth devices.
Courtesy of Aliph

You may not know how to respond if someone asks you "how does noise cancelling work," but it's safe to assume that you've reaped the rewards of noise cancellation technology.

You're walking down a busy street when your phone rings. Do you pick up and shout over the din while straining to hear your caller, or do you miss the call? If you have a noise cancelling headphones, you don't have to choose. Active noise cancellation is designed to eliminate ambient noise so you can have a conversation at a normal voice level almost anywhere. It's does this by using physics, but more on that later.


­Noise cancellation technology can be helpful in many environments. You can use it in the office when you're trying to conduct a business call as your co-workers gab away near your desk. It's a discreet option when you're on a busy street and don't want to shout your credit-card number into your cell phone.

But how does your phone know which voice to pick up? In this article, we'll look at how active noise cancelling works.


The Basics of Noise Cancellation Technology

Time for the magic of science. Noise cancellation works on the principle of sound wave interference. Sound waves are vibrations in the air that can travel over distances and through a variety of mediums. Noise cancelling technology leverages this principle by generating sound waves that are precisely opposite (or "anti-noise") to the unwanted background noise [source: Dragan].

When these opposing sound waves meet, they cancel each other out through a process called destructive interference, resulting in a reduction or complete cancellation of the noise heard by the listener.


How does the microphone know which noise is your voice and what is ambient sound? The microphone on a set of active noise cancelling headphones is actually two microphones — one for your voice, and another for ambient sound — combined into one. This is called a bi-directional microphone. The microphone sends the signal to a sound processor.

The processor then sends the signal across the airwaves so the person on the other end of the call hears your voice. This is sim­ilar to the process of voice transmission featured in hearing aids. Noise-canceling headsets help you hear yourself clearly despite the noise around you, but how do you hear who you're talking to? Read on to find out.


Components of Noise Cancelling Headphones

A display showing designer bluetooth headsets. 
With new designer models like the Plantronics 925, your headset may be confused with the rest of your accessories.
Courtesy of Plantronics

While the microphone is the most complicated part of ANC headphones, there are other features to consider. The earpieces work best when they seal off your ear entirely, though innovation has seen the performance of noise cancelling earbuds improve. Most brands also include earpieces in a variety of sizes so that anyone can get a perfect ear seal.

Headphone design has come a long way since its invention in 1910 [source: Padam]. Noise canceling Bluetooth headphones and earbuds are available in all shapes, sizes, and styles. Sizes continue to shrink and adapt to the changing design needs of the consumer.


Most headsets have connectors and adapters, or they can be synced with a Bluetooth-enabled device. Still, it's always best to check with the manufacturer to ensure your device will work with your headphones.

The Future of Active Noise Cancellation

Technology continues to march forward, and noise cancelling headphones stand to gain too. Shifts in battery life, signal processing, miniaturization, and style promise decades of innovation ahead of us.

Noise cancelling technology has transformed our auditory experience, allowing us to enjoy music, conversations, and silence without the intrusion of unwanted external sounds. As this technology continues to evolve, it promises even greater control over our ability to listen, concentrate, and unwind.


­­­For more information on noise-canceling headsets, please see the links on the next page.

Lots More Information

Related HowStuffWorks Articles

More Great Links


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