A system and method for tuning and controlling ultrasonic handpieces by incorporating a broad-spectrum signal as at least a component of the signal used to drive the handpiece. The response of the handpiece to this broad-spectrum signal is measured and the frequency or amplitude or both of the drive signal are adjusted in order to maintain the desired level of handpiece performance. The operation of the systems and the performance of the methods described enables the handpiece to be operated in a most effective manner over a more widely varying range of mechanical load and thermal conditions than was possible through the use of prior control systems and methods.