Making Soundwave from Transformers Voice for costume?

I am attempting to make one of my favorite toys of all time for my costume this year for Halloween. I am having issues finding a way to have my voice thrown into Soundwave from the Original Transformers. I remember having this device attached to the head of ULTRA Magnus when I was a kid and it kinda sounded like Soundwave. I just do not want to have to pre-record things but rather be able to speak with an attachment in my costume..any ideas you creative people out there?