Audacity is nice but it's more of a visual tool not batch conversion. Using it to convert over 300 files will take long time.
My script does all conversion in couple of minutes automatically. I'm working on an update of improvements

Edit:

It's faster than I thought, only little over 1.5 min for 311 files processed
:
yards-m.ogg maxVol=0.776969 vol=2
you_arrive_at_your_destination.ogg maxVol=0.513778 vol=2
[libvorbis @ 02efe420] Queue input is backward in time
Last message repeated 6 times
you_have_reached_a_viapoint.ogg maxVol=0.666394 vol=2
[libvorbis @ 02ee49e0] Queue input is backward in time
Last message repeated 8 times
you_have_reached_your_destination-e.ogg maxVol=0.160926 vol=2
[libvorbis @ 003fce60] Queue input is backward in time
Last message repeated 7 times
you_will_arrive_at_viapoint.ogg maxVol=0.363999 vol=2
[libvorbis @ 02ee49e0] Queue input is backward in time
Last message repeated 1 times
Processed: 311 Start: 14:57:54.39 End: 14:59:34.13

I need some files to test. Can you give me those truck voice files you're trying to fix; I'm trying out the auto normalization function I've added to see if it works.