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Audio Processing

Audio Processing. Mitch Parry. Resource!. Sound Waves and Harmonic Motion. Properties of Sine Waves. Resonance as Harmonic Frequencies. Nonsinusoidal Waves. Sampling and Aliasing. Quantization. Nyquist and Aliasing. Spectral Domain.

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Audio Processing

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  1. Audio Processing Mitch Parry

  2. Resource!

  3. Sound Waves and Harmonic Motion

  4. Properties of Sine Waves

  5. Resonance as Harmonic Frequencies

  6. Nonsinusoidal Waves

  7. Sampling and Aliasing

  8. Quantization

  9. Nyquist and Aliasing

  10. Spectral Domain • Audio can be represented in the time, frequency, or time-frequency domain

  11. Time Domain • Generate  Silence • Audio Track  Set Rate  Other  2048 Hz. • Generate  Tone

  12. Time Domain 100 Hz Sine wave @ 2048 Hz sampling rate

  13. Frequency Domain… Click here to select all

  14. Frequency Domain • Select all audio from the track • Analyze  Plot Spectrum… • Try this: • Function: Rectangular Window • One spike at 100 Hz.

  15. Spectrogram… Click “Audio Track”  Spectrum Edit  Preferences  Spectrograms  check “show the spectrum using grayscale colors.”

  16. Spectrogram (Time-frequency)

  17. Audio Mixing • Free Multitrack Downloads • http://www.cambridge-mt.com/ms-mtk.htm

  18. “Stop Messing with Me” by Sven Bornemark • Steinberg Grand Piano • Acoustic Guitar • Bass • Drums Overhead • Electric Guitar • Electric Guitar Ambience • Kick Drum • Vocal

  19. Audacity: Mixing Tutorial • Mixing Tutorial

  20. Simple Unmixing • Left: Drums + 0.5 * Vocal • Right: Guitar + 0.5 * Vocal • Remove vocals: • Karaoke track = Left – Right = Drums – Guitar

  21. Audacity: Let’s try it. Real example: Norah Jones

  22. Removing Hiss Hiss_*.wav

  23. Removing Clicks

  24. Short-Time Fourier Transform Spectrogram FFT Each frame contributes one column of spectrogram

  25. Audacity: Let’s try it.

  26. Changing Speed • Downsample • Shorten the clip • Increase its pitch

  27. Changing Tempo • Change length of clip without changing pitch • Split into frames, repeat or remove frames

  28. Changing Pitch • Change pitch without changing length • Increase pitch: Repeat frames and downsample • Decrease pitch: Remove frames and upsample

  29. Audacity: Beat Detection • Drum track

  30. Audacity • Audacity Manual • More Effects and Analyzers

  31. Echo Nest • Echo Nest API • Analyze Documentation

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