This is how to silence an EL transformer, or at least make it quieter, not completely silence it...
Step 1: Tools/materials you'll need
-hot glue gun/epoxy (I used hot glue)
Step 2: Removing the cover
First remove the battery cover by sliding it off. Then turn over the transformer to reveal a screw, it should be easy to unscrew, once removed lift the cover off the transformer revealing the electronics.
Step 3: Adding glue
Now you must add glue to the electronics. It is important that you not go over the edge of the casing so it can close, also do not cover the hole where the screw comes in.
Step 4: Finishing
Replace the cover and tighten the screw.