Unwanted ambient sounds, or acoustic noise, are the reason that noise cancelling headphones were invented. These headphones work by means of active noise control (ANC).
ANC involves the use of one or more microphones placed near the ears, and electronic circuitry that uses the microphones’ signal to generate an antinoise signal. When the antinoise signal is emitted from the speaker driver in the headphones, destructive interference between the sound waves cancels the ambient sounds as heard within the enclosed confines of the noise cancelling headphones.
Noise cancelling technology lets you enjoy music without having the volume at excessive levels, so your sense of hearing does not suffer the adverse effects of excessive volume. Sound can be deceptive, and your hearing adapts to higher volumes. You will be better off if you set your sound equipment at a safe level before your hearing adapts to it.
To establish a safe level of sound, start the volume control at a low setting then gradually increase the volume until you can hear the sound from your noise cancelling headphones comfortably, clearly, and with no distortion. When you have established the safe level, set the volume control and leave it at that setting.
With your audio unit already set to your safe hearing level, you will not have to reset it every time you connect the noise cancelling headphones plug to the audio unit’s headphone jack. You can use a large stereo plug adaptor if the headphone jack you are trying to use is larger than the headphones’ plug. Some jacks in airplane armrests might not match your headphones’ plug or plug adaptor.
The reduction in ambient noise brought about by such headphones available through retail is primarily for low-frequency sounds. For example, the Panasonic RP HC300 headphones with noise cancelling technology reduce more than 18 decibels at 300 Hz.
For higher frequency sounds, a pair of noise cancelling headphones may depend on the soundproofing method to prevent you from hearing such noises. Soundproofing is preferable because it lessens the need for electronic circuitry and at higher frequencies, ANC is less effective. To actually cancel high frequency sound waves coming at your ears from all directions, the cancelling waveform’s sensor and emitter would have to be right next to your eardrums, which is unfeasible technically.
Headphones that make use of noise cancelling technology will necessarily consume power. In the case of the Panasonic RP HC300, an AAA battery (R03/LR03) is included, and this battery lasts 17 hours (R03) or 35 hours (LR03) depending on operating conditions.
A pair of noise cancelling headphones can eliminate airplane engine noise and help you sleep during airline flights. You can also use it against environmental noise in trains and buses.
