• Download Audacity: http://web.audacityteam.org/download/
• Audacity Manual: http://manual.audacityteam.org/

Go to Edit > Preferences

• Devices: Channels = 1 (Mono)
• Quality: Default Sample Rate = 44100 Hz; Default Sample Format = 16-bitrate
• Tracks: Check - Update display while playing; Uncheck - Select all audio in project, if none selected

1. Open all files in one Audacity session and select-all (CTRL-A)
2. Effect > Normalize > Settings: Check remove DC offset; Check Normalize maximum…; -3dB; Uncheck Normalize stereo…
3. Effect > High Pass Filter > Settings: Roll-off = 48 dB; Cutoff = 100Hz
4. Effect > Low Pass Filter > Settings: Roll-off = 48 dB; Cutoff = 11000 Hz
5. Effect > Leveller > Settings: Degree = HEAVIER; Threshold = -70 dB
6. Effect > Compressor > Settings: Threshold = -13 dB; Noise Floor = -60 dB; Ratio = 2.5:1; Attack Time = 0.5 secs; Decay Time = 1.0 secs; Check Make-up…; Uncheck Compress…
7. Effect > Normalize > Settings: Check remove DC offset; Check Normalize maximum…; -3dB; Uncheck Normalize stereo…