What can make a shoebox guitar with 2 rubber bands sound louder?

To make a shoebox guitar with two rubber bands sound louder, you can tighten the rubber bands to increase tension, which will produce a sharper and more resonant sound. Additionally, amplifying the soundbox by placing it on a hard surface or inside a larger container can enhance the volume. Using a larger shoebox or adding materials like a resonant board can also help amplify the sound produced.