nfl jerseys wholesale

Acoustic Noise-Cancellation Development
The idea of personal noise protection by actively controlled headphones was originally documented in a 1960 Russian patent application.[1][2] In the United States,louboutin outlet, the idea for active noise cancellation for helicopter and aircraft pilots was patented by Dr. Lawrence J. Fogel as early as the mid 1950s U.S. Patent 2,866,848, U.S. Patent 2,920,138, U.S. Patent 2,966,549 and Canadian patent 631,136. According to Bose, the company started noise-cancellation involvement after Dr. Amar Bose went on a 1978 flight to Europe, utilized the headphones provided during the flight only to conclude that he couldn't really enjoy the sound with the roar of engines in the background."[3]
In 1986, Bose applied their noise-cancellation technology to develop headphones to protect the hearing of pilots participating in the first non-stop around-the-world flight.[4]
One source notes that "nearly simultaneously,Christian Louboutin Shoes, the US company Bose and Sennheiser in Germany presented active headsets for aircraft pilots,"[1] citing a 1986 American Society of Mechanical Engineers paper about the Bose product and a 1988 Funkschau (see de:Funkschau) paper about the Sennheiser. Bose's first noise-cancelling headsets were released to the public in 1989.
After about 10 years of research and development Bose released their first consumer level noise reducing headphones for pilots called the Aviation Headset, released in 1989. The current revision provides active equalization as well as active noise reduction.
Like all such technology,Christian Louboutin outlet, it mixes an inverted sample of the ambient sound outside the headset with the sound that reaches the inside of the headset,jordans shoes, partially cancelling out the noise. Active (battery-powered) noise cancellation is never perfect, and is better at low frequencies than at high frequencies.[citation needed]
As with all active noise cancellation technologies,louboutin for sale, it requires a source of power—a small battery inside the headset—to perform the cancellation.