I am looking for a way to normalize the sound in MANY MP3 files I have. Some have low sound, while others are louder so I have to turn the volume up or down depending on the song. What ways are there to do this for all files. I specially would like to do it via the terminal but GUI ways are also accepted.
With Audacity we can easily batch process files to apply conversions or effects to many files in a list. To do so we first have to define a "Chain" containing the effects we want to apply.
This is done with "File --> Edit Chains...". In the now opening window press the Add button on the bottom left to insert a new chain (give it a sensible name):
Then choose the effect and it's parameters to insert to the chain (here shown for default values and the Normalize effect).
Important: we always need to also add the effect "Export MP3" (or any other export format) for saving the resulting conversion to disk.
When done leave this window with OK to open "File --> Apply Chain...". Select the Chain we have just created and load all files you need with "Apply to files...". Several files can be selected from the file chooser that opens.
Processed files will be saved in a new subdirectory "cleaned" in the original's path.
From version > 14.3 we can use the sox filter --norm for normalizing audio on the command line or for batch processing:
sox --norm infile outfile
MP3-support is added to Sox with libsox-fmt-all:
sudo apt install sox libsox-fmt-all
