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Active noise control ( ANC ), also known as noise cancellation ( NC ), or active noise reduction ( ANR ), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in ...
Noise -cancelling headphones alongside a carry case. Noise-cancelling headphones are headphones which suppress unwanted ambient sounds using active noise control. This is distinct from passive headphones which, if they reduce ambient sounds at all, use techniques such as soundproofing . Noise cancellation makes it possible to listen to audio ...
A hearing protection device, also known as a HPD, is an ear protection device worn in or over the ears while exposed to hazardous noise and provide hearing protection to help prevent noise-induced hearing loss. HPDs reduce the level of the noise entering the ear. HPDs can also protect against other effects of noise exposure such as tinnitus and ...
QuietComfort 20. The "QuietComfort 20" (QC20) and QC20i in-ear headphones were released in 2015 and are the company's first in-ear noise cancelling headphones. [ 19] It received a 2014 Red Dot Design Award. [ 20] Also, it received a CNET 's Editors' Choice Award of 4.5/5 points for its active noise-cancelling.
Silencer (firearms) A silencer, also known as a sound suppressor, suppressor, or sound moderator, is a muzzle device that suppresses the blast created when a gun ( firearm or airgun) is discharged, thereby reducing the acoustic intensity of the muzzle report (sound of a gunshot) and jump, by modulating the speed and pressure of the propellant ...
Gun safety is the study and practice of managing risk when using, transporting, storing and disposing of firearms, airguns and ammunition in order to avoid injury, illness or death. Gun safety includes the training of users, the design of firearms, as well as the formal and informal regulation of gun production, distribution, and usage. [ 1 ]
History. The Gun-Free School Zones Act of 1990 was originally passed as section 1702 of the Crime Control Act of 1990. It added 18 U.S.C. § 922 (q); 18 U.S.C. § 922 itself was added by the Omnibus Crime Control and Safe Streets Act of 1968 . The Supreme Court of the United States subsequently held that the Act was an unconstitutional exercise ...
Additionally, the discharging of firearms in indoor ranges can produce noise levels of over 140 dB sound pressure level. [18] To combat this, it is commonly recommended that those inside the range "double-up" ear protection by using both earplugs and over-the-head earmuffs, and to protect range bystanders from sound exposure. Depending on the ...