Clever advertisement for Coca-Cola in Brazil. Roll up the magazine with its pre-cut slots, lock into place, and voila...an audio amplified. Watch the video and you might be able to make your own using an old magazine issue laying around the house...
Other DIY speaker and sound amplifiers:
Trio of IKEA Salad Bowls Turned Into DIY Nautilus Audio Speakers
The DIY Smart Phone Speaker Solution Waiting in Your Kitchen
Noel's DIY Plywood iVictrola Speaker Project
Reuse & Recycle: Turn Paper Into Speakers
Via Design You Trust