Three music-loving friends, Emma, Mairi and Isabella, ask Nina how a speaker works. In order to find out, Nina asks sound neuron, beautiful Belle, to help. At Nina's workshop, they open up a speaker and find out what's inside, before heading off to another exciting location.

Originally released by BBC Worldwide Learning, 2009. Streaming video file encoded with permission for digital streaming by Infobase on September 22, 2020.