Does a vibrating spring produce sounds even when they cannot be heard? Use the Thundering Tube amplifier to find out! Pull or shake the spring attached to the rubber drum attached to one end of the Thundering Tube and you will hear an astonishingly realistic “rumbling” sound of thunder. The length of the telescoping tube can be adjusted to “dial” in different resonance frequencies. As you vary the length of the tube, students will hear only the sounds that are in resonance with the column length. Even though numerous sound frequencies are produced by the vibrating spring, they are “silenced” until the tube length changes. This is a perfect demonstration device to explain resonance, amplification, and even musical instruments. One Thundering Tube and complete instructions are provided.