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S kills : Set sample size and rate in Audacity

Recording and encoding analog data. S kills : Set sample size and rate in Audacity C oncepts : analog versus digital data, analog to digital conversion, digital to analog conversion, sample rate, sample size, quality-file size trade off.

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S kills : Set sample size and rate in Audacity

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  1. Recording and encoding analog data Skills: Set sample size and rate in Audacity Concepts: analog versus digital data, analog to digital conversion, digital to analog conversion, sample rate, sample size, quality-file size trade off This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

  2. Where does this topic fit? • Internet concepts • Applications • Technology • Implications • Internet skills • Application development • Content creation • User skills

  3. Analog data But, computers require digital data …

  4. Which clock is digital? Analog? http://som.csudh.edu/fac/lpress/presentations/clocks/clocks.html

  5. A digital clock … 03 02 01 00 04 01.49

  6. Recording and playing sound Computer 10010110 (150) 11001001 (201) 11000111 (199) … Analog to digital converter Computer 10010110 (150) 11001001 (201) 11000111 (199) … Digital to analog converter

  7. Reading and adjusting temperature Computer 10010110 (150) 11001001 (201) 11000111 (199) … Analog to digital converter Computer 10010110 (150) 11001001 (201) 11000111 (199) … Digital to analog converter

  8. Sensors for all sorts of things • Speed • Rate of flow • Pressure • Altitude • Acceleration • Motion • Rotation • Temperature • Light level • Sound • Compass direction • Blood pressure • Heart rate • And more … • The Internet of things

  9. Sampling an analog signal How can we improve the fit of the digital curve? (Hint: 2 ways)

  10. 1. Increase the sampling rate What is the second thing we can increase? Hint: how did we increase the variety of colors in images or symbols in text?

  11. 2. Increase the sample size (more bits per sample)

  12. Recording tradeoffs Increase sample rate → quality ↑ file size ↑ Increase sample size → quality ↑ file size ↑

  13. Increase code bits → quality ↑ file size ↑ Text 2-bits/character Image 1-bit/pixel Sound 2-bits/sample

  14. Set default sample rate and size Edit > Preferences > Quality

  15. Set sample rate and size

  16. Analog Digital What other real world phenomena can we sample and input to a computer?

  17. Summary

  18. Self-study questions At a sampling rate of 8,000 16-bit mono samples per second, what would be the file size for a one minute recording? How much larger would a stereo recording be? How much larger would the file size be if we were to sample at 48,000 samples per second? How much larger would the file size be if the samples were 32 bits each?

  19. Resources Wikipedia analog: http://en.wikipedia.org/wiki/Analog_signal Wikipedia digital: http://en.wikipedia.org/wiki/Digital A more detailed tutorial: http://www.planetoftunes.com/digiaudio/how_a_to_d.html

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