Ch8 Section A: Audio Basics


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Audio Basics

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Ch8 Section A: Audio Basics

  1. 1. Chapter 8<br />Section A: Digital Sound <br />
  2. 2. What is sound?<br />Sounds are pressure waves of air, that pushes on your eardrum slightly, causing you to hear.<br />Our ears are sensitive to these pressure waves, if there wasn't any air, we wouldn't be able to hear sounds. There's no sound in space.<br />
  3. 3. What is sound?<br />When you clap your hands, the air that was between your hands is pushed aside. This increases the air pressure in the space near your hands.<br />
  4. 4. Chapter 8: Digital Media<br />4<br />What is Digital Audio?<br />Digital representation of sound, in other words<br />Music, speech and other sounds represented in binary format for use in digital devices.<br />
  5. 5. Digital Audio Basics<br />To digitally record sound, samples of the sound wave are collected at periodic intervals and stored as numeric data.<br />Chapter 8: Digital Media<br />5<br />
  6. 6. Chapter 8: Digital Media<br />6<br />Digital Audio Basics<br /><ul><li>Sampling Rate refers to number of times per second that a sound is measured, it is expressed hertz (Hz).
  7. 7. One thousand samples per second is expressed as 1,000 Hz (kilohertz).
  8. 8. The height of each sound sample can be saved as an 8-bit number for radio quality recordings or a 16-bit number for high-fidelity recordings.</li></ul>Sampling Size: number of bits in the digital representation of each sample. <br />
  9. 9. Chapter 8: Digital Media<br />7<br />Digital Audio Basics<br /><ul><li>Higher sampling rate = more realistic digital sounds
  10. 10. An audio CD has a sample rate of 44,100 HZ (44.1 Khz), which means that a sample of the sound is taken 44,100 times per second.
  11. 11. An audio CD has a precision of 16-bits sample (bits per second), meaning that sixteen bits are used for each sample, for stereo you must take two 16-bit samples, requiring 32-bits for each sample.
  12. 12. Higher sample sizes allow more dynamic range − louder loudsand softer softs</li></li></ul><li>Digital Audio Basics<br />Sampling is the process of converting an analog signal to a digital signal.<br />Each dot is a “snapshot” and represents one audio sample. <br />
  13. 13.
  14. 14. Digital Audio Basics<br />For CD-quality music at 44.1 kHz, one minute of music requires about 10 MB of storage, 45 minutes of music 450 MB.<br />Chapter 8: Digital Media<br />10<br />
  15. 15. Audio Compression<br />Audio compression reduces the size of sound file by removing bits that represent extraneous noise and sounds that are beyond the frequencies of normal hearing.<br />Advantage: a compressed file requires less storage space than an uncompressed file and can be transmitted faster over a network.<br />Chapter 8: Digital Media<br />11<br />
  16. 16. Chapter 8: Digital Media<br />12<br />Digital Audio Basics<br />Sound cards are responsible for transforming bits stored in an audio file into music, sound effects, and narrations.<br />Digital signal processor<br />Transforms analog waves to digital bits when you make a sound recording<br />Transforms digital bits into analog waves when you play a digital audio file<br />Handles compression and decompression<br />
  17. 17. Chapter 8: Digital Media<br />13<br />Digital Audio Basics<br />The most popular digital audio formats include AAC, AIFF, MP3, RealAudio, Wave, and WMA<br />Audio or media player software allows you to record and play digital audio files<br />You can embed digital audio files into a Web page.<br />Streaming audio plays as its file is downloaded, avoiding lengthy delays (entire file downloaded)<br />
  18. 18. Chapter 8: Digital Media<br />14<br />Portable Audio Players<br />Pocket-sized, battery-powered device that stores digital music.<br />Digital music is available from a wide variety of sources<br />Formats include MP3, AAC, and WMA<br />A series of digital music tracks in a portable device is known as a playlist.<br />
  19. 19. Synthesized Sound<br />While digital audio is a recording of real analog sound signals converted into digital signals, synthesized sound is an artificially created, sound.<br />Synthetic <br />Artificial .<br />Chapter 8: Digital Media<br />15<br />
  20. 20. Chapter 8: Digital Media<br />16<br />MIDI Music<br />MIDI (Musical Instrument Digital Interface) specifies a standard way to store music data for synthesizers, electronic MIDI instruments, and computers<br />MIDI-capable sound cards contain aWavetable (set of prerecorded musical instrument sounds)<br />Does not produce high-quality vocals<br />Does not have full resonance of “real” sound<br />Midi Files have a non-Wave form, they contain instructions as to how to create the sound, rather than a digitized version of the actual sound<br />
  21. 21. Chapter 8: Digital Media<br />17<br />MIDI Music<br />Wav file<br />Midi file<br />MIDI music tends not to have the full resonance of digital audio. <br />
  22. 22. Chapter 8: Digital Media<br />18<br />MIDI Music<br />Music composition software<br />provides tools for entering notes, specifying instruments, printing sheet music, and saving compositions in formats<br />such as MIDI.<br />
  23. 23. Digital Audio Basics<br />Samplers: Instruments that can digitize, or sample audio sounds, turn them into notes, and play them back at any pitch.<br />Synthesizer: An electronic instrument that synthesize (manufacture, create) sounds using mathematical formulas.<br />Sequencers: Interprets the sequence of MIDI commands <br />Slide 19<br />
  24. 24. Music Studio<br />Before:<br />Synthesizers<br />Samplers <br />Other Instruments<br />Today… +<br />Sequencers<br />Virtual instruments <br />Computer keyboards and Music keyboards<br />Professional-level multi-track recording and editing studio that fits in a suitcase.<br />
  25. 25. Electronica<br />Electronic Music technology has transformed the world of a musician<br />Electronica: Music designed from the ground up with digital technology<br />Some of the most interesting sequenced music.<br />Unleash the musician in the rest of us.<br />No limits, can go from Classic to Rock<br />Slide 21<br />
  26. 26. Digital Audio Basics<br />Sound Data is also called Waveform Audio<br />Sound Editing is the manipulation of a visual image of the sound's waveform.<br />Chapter 8: Digital Media<br />22<br />
  27. 27. Change a sound's volume<br />Change a sound's pitch<br />Add special effects<br />Echoes<br />Remove irrelevant noises<br />Rearrange musical passages<br />Include voices (or mix) <br />Include non-electronic instruments in the mix.<br />Slide 23<br />Sound Editing Software<br />
  28. 28. Chapter 8: Digital Media<br />24<br />Speech Recognition and Synthesis<br />Speech synthesis is the process by which machines produce sound resembling spoken words<br />Phoneme: a basic sound unit, like a syllable, that are stringed together to form words.<br />Text-to-speech software: generate sound played through your computer’s standard sound card.<br />Key technology in mobile comunications<br />
  29. 29. Chapter 8: Digital Media<br />25<br />Speech Recognition and Synthesis<br />Speech recognition or voice recognition refers to the ability of a machine to understand spoken words<br />Speech recognition software is in charge of processing words spoken into a microphone that’s attached to the sound card (that is in charge of changing the analog data into digital data).<br />
  30. 30. Chapter 8: Digital Media<br />26<br />Speech Recognition and Synthesis<br />
  31. 31. Chapter 8: Digital Media<br />27<br />