Audio mastering
Audio mastering is the process of preparing audio for playback on a wide range of playback devices. The main changes to a track during mastering are: tonal balancing and level adjustment. The former is primarily done with equalisation while the latter is primarily achieved with compression. Other effects that can be used during mastering are: audio enhancers, audio exciters and noise reduction to eliminate hum and hiss.
- Normalize the tracks to set the highest peaks in audio volume to a preset level; the overall audio should never exceed 0 dBfs.
- Equalize audio between two tracks to ensure there are no jumps in bass, treble, midrange, volume or pan.
- Apply a compressor (for example, 4:1 starting at -6 dB) to compress the peaks but to expand the softer parts.
- Apply a dynamics compressor to compress only specific frequencies that generate the audio peaks.
- In the case of mastering for broadcast, the bandwidth of the signal has to be reduced. For example for TV broadcast: apply a high pass filter at 80 Hz with -18 dB/octave to filter out low frequencies and apply a low pass filter at 12 kHz with -9 db/octave to filter out high frequencies.
