The magnitude of the sonic boom is not relative to mass. It is relative to the altitude and to the speed of the aircraft, and the duration and maximum amplitude of the shock wave are dependent on the shape of the aircraft.

You may have misread an article describing pounds-per-square-foot as a measure of sonic boom intensity. This measurement is not about the mass or density of the aircraft relative to its area, this is the change in air pressure at the ground caused by the sound wave.