ffmpeg: Normalize audio in an avi file
You can use ffmpeg with the compand audio filter (a port of sox effect filter of same name) to &quot;compress or expand the audio's dynamic range&quot;, but admittedly this is one of the more complicated audio filters.
Example from the documentation
Make music with both quiet and loud passages suitable for listening to in a noisy environment (whatever that means):
ffmpeg -i input -filter_complex \
&quot;[0:a]compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2[audio]&quot; \
-map 0:v -map &quot;[audio]&quot; -codec:v copy output

The video is stream copied (re-muxed) in this example since you probably don't want to touch the video.