Step 1: What you need
-Piezoelectric buzzer, mine is quite large and came from a telephone ringer
-Some wire, both stranded type (if your leads from the piezo element aren't long enough) and safety wire (if you want a super ghetto attachment system like me)
Step 2: Connect the leads
Now, connect the black lead to the part of the 1/4" phono jack that is like a ring; the ground. Next connect the red one on to the part that connects to the J looking thing; the positive.
You should end up with something looking like this \/
Step 3: Removing the "lid" off the can.
The way I did it was to sand lip on the drinking side on a belt sander until the "lid" relased. If you don't have a belt sander, well, figure something out, it's not to hard.
Step 4: Cut a hole in the "lid"
I traced out my buzzer first, then started a cut with a dremel, but then I got lazy and just ripped it from there (beast, I know). I of course cleaned up the jagged rip marks with a sanding bit.
Then test fit! Cool, it fits!
Step 5: Put a hole in it.
Then just put the jack through, and screw on the nut, good and tight!