- Waveforms
- X axis: time
- Y axis: amplitude
- Amplitude envolope: variation of amplitude over time
- Frequency: number of cycles (time between two peaks) per second (Hz); 20 - 20000 Hz
- Phase: offsets between two waves
- In phase: every peak aligns
- Out of phase: phase cancellation - trough with peaks
- Beating: frequency slightly different; in phash and out of phase appear alternatively
- Loudness: amplitude in linear (db), loudness in logarithm (+10 db = 2 * Loudness)
- Pitch:
- Harmonic Series (linear): 100, 200, 300, 400, ... Hz (may get different notes)
- Octaves (log): 100, 200, 400, 800, ... Hz (always the same note if doubled)
- Fletcher - Munson Loudness Curves: changes amplitude versus frequencies to get equally loud sound
- Spectra: energy over different frequencies
- Fourier Theorem: any periodic waveforms can be represented as sum of sine waves whose frequencies are integer multiples of the fundamental frequency
- Envelope and Sonogram: frequencies over time, color representing db