General Info On Noise-Cancelling Headphones

What Are Noice-Cancelling Headphones?

Noise-canceling headphones reduce unwanted ambient sounds (i.e. acoustic noise) by means of active noise control (ANC). This involves using one or more microphones placed inside the headphone and near the ear, plus some electronic circuitry that uses the signal from the microphone to generate an "antinoise" signal. The theory behind ANC is that by picking up ambient sound inside the headphone earcup with a microphone and reproducing it out of phase, the background noise can be actively cancelled or "nulled" out. The microphone inside the headphone detects both the music and the background noise, and the ANC functions to produce an antinoise signal, which is sent back through the speaker driver in the headphone to create destructive interference that cancels out the ambient noise.

Noise cancellation also involves passive means, as used in traditional headphones, where a fully-encapsulating earcup with insulating foam (also called circum-aural headphones) blocks out some of the noise from outside the headset.

Typically, ANC is used to cancel the lower-frequencies of the background noise, while passive methods are used to suppress the higher frequencies, where active cancellation is less effective.

Noise-cancellation makes it possible, for instance, to enjoy music without raising the volume too much. Or, it can help a passenger sleep in a noisy vehicle (such as an airliner). The continuous hum of an airliner allows the noise-canceling method to be particularly effective, and some airlines offer noise-canceling headphones to their first and business class customers.

 

History of Noise-Cancelling Headphones

Noise-canceling headphones were invented in 1988 by Amar Bose, the founder of the Bose Corporation. Mr. Bose was travelling on a commercial jetliner, listening to music on headphones provided by the airline company. The background noise from the plane’s engines interfered with his enjoyment of the music. Bose wondered how he could eradicate the surrounding noise without spoiling the quality of the music, and the result was the noise-canceling headphone.

Limitations of Noise-Cancelling Headphones

Noise-canceling headphones have a few limitations. The most important are:

• They work better against continuous sounds (airline cabin, refrigerator or air-conditioning hum, etc.), and are much less effective against speech or other rapidly changing audio signals.


• They also can be overloaded by low-pressure frequency waves, distorting the desired signal.


• They may introduce additional noise - usually in the form of high-frequency hiss.


• They may pick up stray electromagnetic fields, such as mobile phone signals, and convert them into unwanted noise.


• They consume power, which is usually supplied by a USB port or a battery that must occasionally be replaced or recharged.


• They are usually heavier and bulkier than traditional headphones, because of the use of batteries. Newer models are less bulky, but still require batteries, which make them heavier than traditional headphones.

Are Noise-Canceling Headphones Safe?

According to an expert, Dr. Andrew Weil, noise-canceling headphones can be beneficial, since both loud noises and constant low-level noise can lead to health problems. Acute loud noises can damage hearing, interfere with sleep, raise blood pressure and stress levels and cause headaches. Dr. Weil actually recommends noise-canceling headphones to help avert the health problems noise exposure can present.