The Different Types of Noise Canceling Headphones

For music aficionados there’s nothing quite like settling in to a comfortable chair, slipping on the set of headphones, and listening to wonderfully reproduced music as it flows into the ears and stirs the soul. Yet another thing these same people know is that ambient sound can completely ruin the experience. For example, you may be preparing for the red-eye flight from Los Angeles to New York with the expectation that you’ll pass the hours with your favorite Yanni tunes. But once you realize you can still hear the plane’s engines it’s all over.

It just so happens that this very scenario was the thing that prompted the research and eventual development of noise canceling headphones. The creator of this wonderful invention is none other than Amar Bose, whose 1978 flight set him on the path to develop a commercially viable product that would be released some 10 years later. Thanks to his engineering noise canceling headphones are now a staple for frequent flyers.

Passive Noise Canceling

There are only two types of noise canceling headphones: passive and active. Passive headphones achieve noise reduction without the use of additional electronics. In other words, ambient sound is reduced by using specific materials known to absorb sound, as well as a design which allows the headphones to completely enclose the ears. Between the two, passive noise canceling headphones can reduce ambient sound by up to 30 dB.

While passive headphones are good for some situations, the two biggest problems are weight and limitations. Because the headphones are packed with heavy, dense materials, the overall weight is significantly greater than most other headphones. Extended use can cause headaches, ear pain, and other physical issues, which may not be worth it when you figure in the second factor of limited noise reduction. That same jet engine for example, can be as high as 90 dB. Thankfully there is an alternative.

Active Noise Canceling

Active noise canceling headphones are much more effective and can reduce ambient sound by an additional 20 dB or more. They are called “active” because they rely on electrical energy to work. In other words, active headphones have a battery. They work on a principle called “destructive interference”; a principle in which incoming sound waves from ambient noise are met with equal waves of opposite force, canceling one another out.

In plain English, sound waves produce a series of highs and lows as a result of the vibration that produces them. Think of these highs and lows as crests and valleys. With active noise canceling headphones, a speaker monitors incoming sound and measures the crests and valleys. An electronic chip within the headphones then reproduces its own sound wave with crests and valleys of the exact same height and depth. The only difference is that their phase is reversed.

When the outgoing sound waves meet the incoming ones, crest meets valley and vice-versa. The result is a canceling out of the incoming ambient sound. Although this method cannot completely erase ambient sound, combined with some aspects of the passive headphones it can come pretty darn close.