Acoustic amplifiers have been around for a long time. In fact, you can purchase them online to get better sound out of your music players. You could also build your own using simple tools available in every home. hboom has put together a video that shows you how to build an acoustic amplifier using a Pringles can:
You are going to need a Pringles box, Popsicle sticks, glue, a saw, plywood, rubber bands, and some paint to get started. You can find the step-by-step instructions on Instuctables.com.