There are plenty of people that make good use of noise cancelling earbuds and enjoy the benefits they can provide. Even so, anyone that has every owned a pair will tell you that the technology is not without its issues. None of these have to be show stoppers that ruin the experience. It is helpful though to be aware of these points before you jump in and purchase some.

White Noise

There is typically a small amount of white noise involved with using headphones or earbuds with noise cancelling technology. This problem is generally minimal. Most people will tell you that they simply get used to it. Yet personal opinions vary as to what the threshold is between minor background noise and an unacceptable annoyance. If you are flying, on a train or in any other situation where you would like to shut a constant noise like a jet engine, a bit of background white noise is not much of an issue. On the other hand if you are an audiophile and are looking for a perfect sound system – you want exquisite sound reproduction and noise cancelling capability – then you might be a bit perturbed by this issue.

Power/Batteries

The noise cancelling capabilities work through creating sound waves that literally cancel the unwanted sounds. Creating sound waves takes energy. Noise cancelling earbuds therefore need to have a power source. This is typically a small addition, in the form of a small box, that is added somewhere along your earbud’s wires. Clearly this added bulk is not very welcome. Manufacturers realize the bummer factor associated with having something more added to the typical earbud/wire arrangement. Some effort is usually made to create a battery/power system that is not too intrusive or uncomfortable. Perhaps unsurprisingly it is the more expensive earbuds that tend to have more effort put into design and ergonomic considerations. They tend to have more elegant solutions to the “have to have a power source” problem.

The need for power also creates another issue. When you are using your headphones away from home your batteries may run out of juice. Depending on your earbuds, this can mean the sound cancelling will not work or it can mean your earbuds will not work at all.

Noise Cancelling Amplifier

Each earbud has two sound producing systems. One system recreates the sound you want to hear: music, the radio, an audio book, etc. The other sound production system creates the sound waves that disrupt and wipe out the unwanted sounds: jet engines, bus motors, etc. Most active noise cancelling earbuds have longer earpieces than slimmer models that can practically disappear once they are placed into your ears. Even so, many noise cancelling earbuds are only slighter larger.

Some sounds are cancelled well and others, not so well.

Constant sound or noise is generally what sound cancelling does a great job with. Problems arise with sudden or uneven sounds. A variably timed and sharp clanging or banging, for instance, is harder to filter out. This also applies to someone sitting behind you on a plane that is excitedly talking and regularly varying the modulation of their voice. Interestingly if you put this same person into a crowded room where many people are talking, everyone’s voices form a din that noise cancelling can handle quiet nicely.

Baby with earbuds photo courtesy creative commons license, image provided by http://www.flickr.com/photos/inferis/227667437/

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The idea behind noise cancelling earphones is to actively cancel out the noise from your surroundings. This is done by producing sound waves that cancel the environmental noise. The details of this are explained in more detail below.

Noise cancelling technology involves four different components. First there is a power source to provide the energy to run the system. Typically this involves a battery or two. Second is a sound detector for assessing incoming noise. Third is a processor, which actually serves two purposes. It determines the frequency of incoming sound and sends out the signal for the sound that will cancel the noise. Fourth is the speaker that emits the noise cancelling frequency.

The idea for this form of noise cancellation was first patented in 1930 by Paul Lueg. This work acknowledged the fact that a noise and its mirror wave, exactly out of phase, could cancel each other out. In the 1980′s the US Airforce and Amar Bose perfected a headphone system of active sound cancellation that cancelled incoming noise within the ear canal in the 1980s. This advance lead to the modern day headphone and earbud applications we use today. Bose headphones with active noise cancelling are still offered for sale today, as are a number of other brands.

Bose QuietComfort 3 Noise Cancelling Headphones

JVC HANC250 High-Grade Noise Cancelling Headphones

Audio Technica ATH-ANC7B Active Noise-Cancelling Closed-Back Headphones

In theory noise cancelling technology is just as easily built into earbuds as it is into headphones. In reality it is a bit of challenge. Adding a battery fueled power source, a device to assess incoming sounds, a processor to determine the frequency of the sound cancelling waves that are needed and more sound reproduction transmitters to headphones is not problematic. Earbuds are another matter. They are not bulky and ideally should be unobtrusive and virtually unnoticeable.

Sound Waves and Noise Cancellation

Sound is produced by waves moving through air. All waves have peaks and trough and with a steady sound the distance between each repeating part of the wave is defined by a set distance (the wavelength). So the distance from one trough to the next or from one peak to the next peak is the same distance away. The trick with effectively negating this wave is to produce the same sound but with one important feature related to its timing. The sound cancelling noise is exactly out of phase with the noise you want to eliminate. This means that when the two sound waves meet the trough of the original noise is being met by a peak of the sound cancelling wave. The end result is an entirely flattened sound profile.

Baby with headphones photo courtesy creative commons license, http://www.flickr.com/photos/gideon/429590768/

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