The voice trembled. The vibrato aluminum piano is caused by the continuous sound produced when the aluminum sheet is struck, which is caused by the * * * vibration * * *. Generally speaking, the transverse vibration caused by detonation is transmitted on the aluminum plate, reflected at the end face, and the incident wave and the reflected wave are superimposed to form a standing wave. For aluminum plates with free ends, both ends are antinodes of standing waves.