Here’s a project sure to head off your road rage. Instead of silently fuming the next time you’re stuck in traffic behind some attention-deficient driver who fails to move when the light turns green, just give him a friendly yet firm word of encouragement through your DIY megaphone. He’ll definitely get the message. The device projects your voice using a small microphone connected to a preamplifier and boosted with a power-amplifier circuit. It won’t deafen anyone, but it can provide a step up to more than twice your normal speaking volume.