Longitudinal standing waves can be excited on helical springs. Through optical projection, nodes and antinodes are made visible. A horizontally mounted small helical spring is projected onto the wall of the lecture hall. A standing longitudinal wave is excited by driving one of its ends with a door bell vibrating at one of the normal mode frequencies of the spring. In the projection, the nodes and antinodes of the longitudinal vibration are easily seen: In the nodes, the sections of the spring are motionless and thus clearly imaged, while in the antinodes they appear fuzzy.