I spent a lot more time trying to find out how to do it so I’m making this quick post so I have the info for next time. I found I could run all the files through a batch process in Audacity to normalize them. The files produced by seemed to have a lower audio level than I expected. In my last post Using Text to Speech online tools to create audio files for Arduino projects I had some info about online text to audio sites I have been using to create audio alert files for projects.