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.