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  2. Noise-cancelling headphones - Wikipedia

    en.wikipedia.org/wiki/Noise-cancelling_headphones

    Noise-cancelling headphones are headphones that suppress unwanted ambient sounds using active noise control (ANC). Active noise cancellation makes it possible to listen to audio content without raising the volume excessively. In an aviation environment, noise-cancelling headphones increase the signal-to-noise ratio significantly more than ...

  3. Active noise control - Wikipedia

    en.wikipedia.org/wiki/Active_noise_control

    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 ...

  4. PDF - Wikipedia

    en.wikipedia.org/wiki/PDF

    PostScript is a page description language run in an interpreter to generate an image. [ 6 ] It can handle graphics and has standard features of programming languages such as branching and looping. [ 6 ] PDF is a subset of PostScript, simplified to remove such control flow features, while graphics commands remain.

  5. AOL Mail

    mail.aol.com

    Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!

  6. E-reader - Wikipedia

    en.wikipedia.org/wiki/E-reader

    E-reader. Amazon's Kindle Keyboard e-reader displaying a page of an e-book. An e-reader, also called an e-book reader or e-book device, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals. [1][2] Any device that can display text on a screen may act as an e-reader; however ...

  7. Health effects from noise - Wikipedia

    en.wikipedia.org/wiki/Health_effects_from_noise

    Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. [3][4] Changes in the immune system and birth defects have been also attributed to noise exposure. [5] Although age-related health effects (presbycusis) occur naturally with age, [6] in many ...

  8. Microphone - Wikipedia

    en.wikipedia.org/wiki/Microphone

    The self-noise or equivalent input noise level is the sound level that creates the same output voltage as the microphone does in the absence of sound. This represents the lowest point of the microphone's dynamic range, and is particularly important should you wish to record sounds that are quiet.

  9. Refraction (sound) - Wikipedia

    en.wikipedia.org/wiki/Refraction_(sound)

    Refraction (sound) Refraction, in acoustics, comparable to the refraction of electromagnetic radiation, is the bending of sound propagation trajectories (rays) in inhomogeneous elastic media (gases, liquids, and solids) in which the wave velocity is a function of spatial coordinates. Bending of acoustic rays in layered inhomogeneous media ...