Snap Circuits SOUND, the newest addition to the Snap Circuits line up. Learn all about sound and how it is made and heard. Build more the 185 projects to help demonstrate the principles of sound. Features: Contains over 40 Snap-Together parts. Build over 185 exciting projects. Connect the unit to your smart phone and analyze sounds with downloadable apps. Voice changer; Record voice or music and play it back at different speeds. Snap-together parts require no tools and ensure correct connections. Requires 4 “AA” batteries (not included). Clear and concise illustrated manual included and available online.