This subunit starts with an experiment of resonance in a model of a swing. Students can feel that a minor influence can give a great effect. Further on, students perform experiments with strings, including double bass, guitar and the Melde’s experiment on standing waves. After experiments involving sound in air columns follow. At the end of this subunit, some open inquiries are described that students can choose from. The knowledge build in activities 1 to 7 is a good basis to start to work on each of the activities 9 – 11.