Abstract: A state switched acoustic has a stiffness element having a zero potential energy state and a plurality of controllable stiffness states. A mass is coupled to the stiffness element so that the stiffness element and the mass are capable of resonating at a resonant frequency. A system changes the stiffness state of the stiffness element from a first stiffness state to a second stiffness state while the mass is in motion and stiffness element is in a zero potential energy state so as to change the resonant frequency of the transducer. In a method of changing resonant frequency of a mechanical system, a parameter of the system is dynamically changed while the system is in an energy state that will allow changing the resonance parameter without disrupting the resonance of the system.