midtermstudy - History Leon Scott Invents...

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History Leon Scott: Invents phonautograph (1857): did not play back sound; earliest known invention of a phonographic recording device Charles Cros: Non-working model of phonograph with hill and dale movement Thomas Edison 1 st recording ever (Mary Had A Little Lamb) 1877: phonograph ; lightbulb, motion picture camera, edison records o Tin foil wrapped around a 4inch diameter drum o Hand cranked drum revolved at 60rpm o Diaphragm measure pressure waves in air o Machine both recorded and produced recording w/ multi. Machines Edison Effect: vacuum tube insert a plate into bulb to draw off black soot Vacuum tube: amplifies current, provides for electronic recording, radio Walter Weber Discovered tape biasing by accident in 1935 during bandwidth experiments High frequency added in the recording process that greatly reduces background noise and improves recording quality Developed the magnetophone , a tape recorder AG Bell: Bell-Tainter Gramophone: improvements upon Edison o Floating stylus fir clearer conversion to sound o Wax cylinders for greater sensitivity/longetivity o Mechanical foot tread kept revolutions/pitch more constant o Later addition of electric motor Microphone o Change acoustic energy to electric o Mimic wave motion (dynamic mic) o +/- charge created w/ moving armature Emile Berliner: Ahead of his time Flat disk phonograph, magnetic microphone Similar to principles of the Victrola Victrola: Victor talking Machine – RCA Horn to collect sound, which transmitted vibrations via a diaphragm connected to a needle to the disk; only produced, did not record; shellac Used lateral grooves and disks instead of cylinders and vertical grooves + better fidelity, volume; reproducing funnel could allow for group listening - shellac records broke easily; prone to wear from steel needles Les Paul: Bouncing or sound-on-sound multi-track tape recording Valdemar Poulsen: electromagnetic recording Wire recorder (1898): 1 st magnetic tape recorder, which used a steel wire as the recording medium o Sound is recorded by a microphone that transduces sound waves
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to small electrical pulses o In recording on tape, an electrical signal passes through a recording head as the tape is drawn past, leaving a magnetic imprint on the tape’s surface o When the recorded tape is drawn past the playback or reproducing head, a signal is induced that is the equivalent of the recorded signal o This is the 1 st recording medium that is reusable o Poor sound quality and the background noise is loud, very heavy Physics The higher the temp, the faster the speed of sound Low Frequencies bend around corners Standing Waves: opposing waves Phase shift: time delay between 2 waves; inverting a signal When phase is opposite and amps are equal, they cancel each other out Sine wave: only fundamental frequency Wave shape: smooth bc they consist of only fundamental square wave Pressure Waves (use of microphone)
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This note was uploaded on 04/07/2008 for the course MUIN 277x taught by Professor Garver during the Spring '07 term at USC.

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midtermstudy - History Leon Scott Invents...

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