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 • Audio can be represented in the time, frequency, or time-frequency domain

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

Time Domain 100 Hz Sine wave @ 2048 Hz sampling rate

Frequency Domain… Click here to select all

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

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

Spectrogram (Time-frequency)

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

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

Audacity: Mixing Tutorial • Mixing Tutorial

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

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

Removing Hiss Hiss_*.wav

Removing Clicks

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

Audacity: Let’s try it.

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

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

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

Audacity: Beat Detection • Drum track

Audacity • Audacity Manual • More Effects and Analyzers

Echo Nest • Echo Nest API • Analyze Documentation

Audio Processing

Télécharger la présentation

Plus de contenu associé