The sound is right, but it lacks volume and is not low enough. The engineers decide to go back to the state of the art approach, which this time consists of listing the sound amplifiers already used in the music world. Following a new series of tests, the solution is found. A resonator is required. Amplification is made possible by an ariel coupling between the metal plate and a double membrane resonator. This solution not only amplifies the sound but also produces the sought after low frequency sound. In other words it is a second physical phenomenon used for this instrument. After 6 months of research, the goal had been reached.