History
By the 1950s, systems were created to cancel the noise in helicopter and airplane cockpits. Noise-cancelling aviation headsets are now commonly available.
Currently, most noise-cancelling headsets use analog technology. This is in contrast to other forms of active noise and vibration control in which digital processing is the standard method.
A number of airlines provide noise-cancelling headphones in their business and first class cabins. Noise cancelling is particularly effective against airplane engine noise. In these cases, the headphones are about the same size as normal headphones. The electronics, located in the plane handrest, take the sound from the microphone behind the headphone, invert it, and add it back into the audio signal, which reduces background noise, resulting in a more enjoyable audio experience.
Read more about this topic: Noise-cancelling Headphones
Famous quotes containing the word history:
“Like their personal lives, women’s history is fragmented, interrupted; a shadow history of human beings whose existence has been shaped by the efforts and the demands of others.”
—Elizabeth Janeway (b. 1913)
“If man is reduced to being nothing but a character in history, he has no other choice but to subside into the sound and fury of a completely irrational history or to endow history with the form of human reason.”
—Albert Camus (1913–1960)
“The reverence for the Scriptures is an element of civilization, for thus has the history of the world been preserved, and is preserved.”
—Ralph Waldo Emerson (1803–1882)