.mov file plays, but no sound

What Kind of mov file - what origin / resolution / audio-format?

Does anyone know why a .mov file will play on the iPad, but no sound will play with the movie?

Normally in such cases, the first step is to open the file in the QT Player (or similar application) and to check that file, in fact, does contain audio and, if so, what compression format was used to create it. This information should be found "Inspector" or "Properties" window of files that will open in the WT Player or in the Finder "Info" window for files that will not open in the QT Player. Once you have this information, simply check to see if it is one that is supported by the iPad. If not, the re-compress the audio compression format to one that is iPad compatible. Depending on the software available, it may not be necessary to touch other data tracks.