9781423901402_PPT_Ch06 - Information Technology in Theory...

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Chapter 6 Digital Audio Technology Information Technology in Theory By Pelin Aksoy and Laura DeNardis
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2 Objectives Understand the physical and mathematical basis of sound waves Recognize the amplitude, frequency, and phase properties of sound Apply the three-step process for audio digitization Understand and apply the Nyquist Sampling Theorem Information Technology in Theory
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3 Objectives (continued) Recognize the need for digital audio compression Explain how music files can be compressed without significant sound quality degradation Understand the difference between lossy and lossless compression techniques Become familiar with popular digital audio formats like MP3, WMA, WAV, AAC, and AIFF Information Technology in Theory
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4 Recording Sound The phonograph, invented by Thomas Edison in the late 1800s, was the first device created for sound recording and playback The tin-coated cylinders of the early phonograph were ultimately replaced by vinyl records Another early analog recording technique from the late 1800s relied on magnetism and electricity The magnetic recording approach was adopted by the music industry, and magnetic tapes replaced metallic wires as a recording medium This type of recording technique was later used to store music on audiocassettes, but its popularity diminished in the wake of CDs, flash drives, and alternative storage media Information Technology in Theory
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5 Recording Sound (continued) Information Technology in Theory
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6 Creating Sound Sound is caused by physical disturbances of air molecules This transfer of energy among molecules creates a mechanical wave of energy called a sound wave , which propagates away from the source of the disturbance The creation of sound waves is usually compared to the formation of water waves Information Technology in Theory
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7 Creating Sound (continued) Information Technology in Theory
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8 Converting Between Sound and Electricity To digitize sound, electrical systems must convert mechanical sound waves into electrical sound waves —in other words, into an electrical audio signal Microphones capture sound waves and convert them into an electrical form, while speakers convert the electrical signal back into sound waves The electrical fluctuations correspond to the pressure fluctuations of the sound wave Information Technology in Theory
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9 Converting Between Sound and Electricity (continued) This electrical signal can then be converted into a stream of bits by passing through an audio digitizer Such digitizers are found in sound cards embedded within computers and in chips within Cellular phones To understand the process of audio digitization, you must understand some additional properties of sound Information Technology in Theory
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10 Converting Between Sound and Electricity (continued) Information Technology in Theory
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11 Converting Between Sound and Electricity (continued) Information Technology in Theory
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This note was uploaded on 06/14/2011 for the course CIS 3003 taught by Professor Bauer during the Spring '11 term at University of Central Florida.

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9781423901402_PPT_Ch06 - Information Technology in Theory...

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