A fun instructable from talbotron22 “Here I show how you can very simply modify a megaphone to accept 1/8” line input from an iPod, and mount the megaphone on top of a motorcycle helmet. The resulting “Mega Helmet” delivers the maximal aural stupidity allowed by law…Go play softball wearing the helmet. It is very good for antagonizing the pitcher, and trash-talking in general. The helmet allows both for amplification of your voice, and playback of mp3s from the iPod.” Link.
HOW TO – Make a Megaphone Helmet