Rags Yes you can, but be careful how you do it as it might cause you a bit of extra work.
Firstly copy all your lyrics to a backup file just in case and its always good to have all your lyrics backed up outside your ST3 environment just in case plus it gives you easy access to all your lyrics.
Make sure when you create your new file it is the exact same file with the same name , if you use a file thats been edited you might find your time-coded lyrics wont align properly so you will have to re enter your timecodes.
But if you simply find your .Wav file in ST3 folder load it to a DAW convert it to another format and save it back to ST3 as a new file same name you can then copy paste the lyrics in to it and get rid of the .wav in ST3 folder and you're done.