As long as you use relative paths for your audioUrlMp3 and audioUrlOgg entries (relative to the HTML page containing the gallery's embedding code), the audio should play OK when the gallery is run locally (from a hard drive or a DVD rather than from a web server).
For example, if you create a gallery with JuiceboxBuilder-Pro and then put your audio files (in this example named 'music.mp3' and 'music.ogg') directly in your gallery folder (alongside the 'config.xml' file and the 'images' and 'thumbs' folders), then the audioUrlMp3 and audioUrlOgg entries should look like this:
audioUrlMp3="music.mp3"
audioUrlOgg="music.ogg"
For another example, if you created a new folder named 'audio' inside your gallery folder and put your audio files inside this folder, then the audioUrlMp3 and audioUrlOgg entries should look like this:
audioUrlMp3="audio/music.mp3"
audioUrlOgg="audio/music.ogg"
Please note that Juicebox galleries will run locally only in Firefox and Safari. Please see this FAQ for details:
When I view my gallery locally, I see the message "Juicebox can not display locally in this browser". Why?