A megaphone is a very simple sound device to create. Sending a sound through a cone or funnel-shaped object will amplify its sound. You can wrap any sturdy yet flexible material--even something as simple as poster board--into a cone, and it becomes an instant megaphone. It also is fairly simple to take it to the next level with an electric megaphone. You just need a microphone and a self-powered speaker to connect to your conical object.
Fold a sheet of construction paper or poster board that is 15 inches square into a cone. Cutting off one corner of the paper to round it off will help in folding. If you are making an electric megaphone, you'll need something even sturdier, like lightweight cardboard.
Tape the paper together to make the largest cone possible; the edges of the paper should barely overlap one another.
Cut and trim the ends of the cone to make it close to a perfect cylinder. Trim the large open end so there are no edges pointing out. Cut a hole in the other end big enough to place your mouth or a speaker through. If you don't want an electric megaphone, your task is complete.
Connect a microphone to a small stereo speaker. The speaker needs its own power supply and amplifier; a battery-powered speaker meant for MP3 players will do. If the microphone has a large stereo plug and the speaker has a mini-stereo port, get a large-to-mini adaptor.
Place the speaker within the mouth end of the megaphone; measuring the speaker beforehand so you can make the hole big enough will help. Use strong adhesive tape to secure the speaker within the cone, but make sure the part with the speaker's on/off switch stays outside the cone.
Strap the microphone and its cable to the bottom of the speaker/cone with more tape. The best set-up is to have the speaker's on/off switch at the top of the megaphone and the microphone at the bottom.
Make sure the speaker has fresh batteries, turn it on and speak into the microphone. Your voice will come out of the speaker and be magnified by the cone.
Taping down the microphone is only needed if you want a one-handed set-up. You can leave the microphone and cord free, where you would instead hold the microphone in one hand and the speaker/cone in the other. For an even sturdier cone, cut off the spout end of a large clean funnel. You will need tools that can cut through metal or hard plastic, so use extreme caution.