subject: How do sounds cancelling headphones work ? [print this page] How do sounds cancelling headphones work ?
Although noise cancellation technology had existed as early as the 1950s in airplane and helicopter cockpits it was not until the 1970's that founder of the electronics company Bose , Dr Amar Bose , created and marketed the first commercially available product. Many people today take advantage of noise cancelling headphones to eliminate sound from their environment. Popular applications include reducing sound while travelling on airplanes ( engine noise ) and reducing sound while studying or reading ( street noise, neighbours etc ). Just how noise cancelling headphones work is understood by most users - the headphones themselves produce noise that is in effect the opposite of the noise you are trying to remove. But what exactly does that mean ?
Sound itself is a wave that is composed of a compression phase and a rarefaction phase. Noise cancelling technology produces a sound wave with what is known as a an antiphase ( i.e a wave with the same amplitude but with an inverted phase). Imagine a positive and negetive value combining to cancel each other out. Noise cancelling headphones make use of tiny microphones to sample the environmental noise and then emit a sound opposite to that which is samples.
In theory this should be able to cut 100% of all noise however due to other limiting factors , modern noise cancelling headphones , especially the more expensive top of the range ones can expect to effectively reduce about 85% of noise. However this number is also limited in that these type of headphones are most effective when sampling a continuous sound such as that of an engine or a motor from household appliances. When combatting short bursts of sound such as a conversation or the stop and start sounds of traffic the technology is less effective.
For this reason most noise reduction headphones manufactures target their advertising at travellers and industrial users. Noise cancellation headphones are also able to let you listen to music with the noise cancellation technology system active. This allows one to continue to enjoy listening to music without the need to increase the music's volume. Modern day noise cancelling headphone technology usually attacks noise at the lower end of the frequency spectrum ( bass to mids ). Higher frequency sounds are filtered through traditional soundproofing methods found within any good quality high-end headphone designs.
One of the immediate downsides of using noise cancelling headphones is their reliance on a power source to run the cancellation circuitry. All require batteries to operate. A number of headphones have their battery compartmen tintegrated into the headphones cable which may be rather bulky however a number of modern noise cancellation phones have their batteries housed within the headphone cans themselves.
