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.
Step 1: Get a motorcycle helmet
Get a motorcycle helmet. I picked up this Honda one at a yard sale for $5.
Step 2: Get a megaphone
Get a megaphone. Here I am using a Radio Shack 32-2038A 10 watt one. It is pretty loud.
Step 3: Take out the guts
Remove the batteries and open the housing for the circuit board. This is accomplished by taking out 3 screws on the back of the megaphone.
Step 4: Prepare the 1/8" plug
Trim the ends off of two lenghts of wire. Tin them and solder to the 1/8" plug. Ground goes to the outer of the two leads (here I have made ground the red wire, oops).
Step 5: Run wire into circuit board housing
Remove the handle from the megaphone, drill a hole through it, and run the wires from the plug into the body of the megaphone.
Step 6: Solder the wires onto the circuit board
Solder the wires onto the circuit board. Ground goes to "ground" and the other wire from the plug goes to "in."
Step 7: Screw everything back together
Reattach the handle to the base, and put the circuit board back in.
Step 8: Attach the megaphone to the top of the helmet
Place the megaphone on top of the helmet and attach using copious amounts of duct tape. About 1/2 roll should be enough.
Step 9: Attach the microphone
Put the microphone on the inside of the mouth portion of the helmet. Attach using wire. On this helmet it was really easy because there was already a mesh grill by the mouth.
Step 10: Mount the iPod
Put the iPod on top of the helmet, like the cherry on top, and attach the 1/8" M to 1/8" M cable to the plug on the megaphone.
Step 11: Play softball
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.