Some embodiments provide a method of providing ultrasound energy having a stable power output. The method can comprise providing ultrasound energy from a ultrasound transducer; determining a power level threshold of the ultrasound energy; monitoring a power level of the ultrasound energy over time of the ultrasound energy; communicating a power level to a controller; adjusting the frequency of the ultrasound energy upon a change in the power level; and maintaining the power level threshold of the ultrasound energy.