Dale - Computer Science Illuminated 99

Dale - Computer Science Illuminated 99 - digits A low...

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72 Chapter 3 Data Representation CD surface laser receptor Figure 3.9 A CD player reading binary information lower than that, the human ear begins to hear distortions. A higher sampling rate produces better quality sound, but after a certain point the extra data is irrelevant because the human ear can’t hear the difference. The overall result is affected by many factors, including the quality of the equipment, the type of sound, and the human listening. A vinyl record album is an analog representation of the sound wave. The needle of a record player (turntable) rides up and down in the spiral groove of the album. The rise and fall of the needle is analogous to the voltage changes of the signal that represents the sound. A compact disc (CD), on the other hand, stores audio information digi- tally. On the surface of the CD are microscopic pits that represent binary
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Unformatted text preview: digits. A low intensity laser is pointed at the disc. The laser light reflects strongly if the surface is smooth and reflects poorly if the surface is pitted. A receptor analyzes the reflection and produces the appropriate string of binary data, which represents the numeric voltage values that were stored when the signal was digitized. The signal is reproduced and sent to the speaker. This process is shown in Figure 3.9. Audio Formats Over the past few years there have been several popular formats for audio information, including WAV, AU, AIFF, VQF, and MP3. All of these are based on the storage of voltage values sampled from analog signals, but all format the details of the information in different ways and all use various compression techniques to one extent or another....
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