A system for controlling vibrations of a tip of an ultrasonic handpiece, the system comprising: an ultrasonic handpiece comprising: a tip defining a lumen to provide suction at a surgical site, and a transducer coupled to the tip and configured to vibrate the tip responsive to receiving an AC drive signal; and a control console coupled to the ultrasonic handpiece, the control console comprising: a signal generator for generating the AC drive signal applied to the transducer, a sensor for measuring a voltage of the AC drive signal, a sensor for measuring a current of the AC drive signal, and a processor coupled to the sensors and the signal generator, the system characterized in that the processor of the control console is configured to: determine a first displacement level for the tip that is a maximum displacement level for the tip, receive a tissue response model defining a stiffness threshold and second displacement levels for the tip that are each less than the first displacement level and associated within the tissue response model with a different potential tissue stiffness value greater than the stiffness threshold, determine a tissue stiffness value of tissue being contacted by the tip based on the measured voltage and current of the AC drive signal, determine whether the determined tissue stiffness value is less than the stiffness threshold, responsive to determining that the determined tissue stiffness value is less than the stiffness threshold, set a target displacement level for the tip to the first displacement level, responsive to determining that the determined tissue stiffness value is greater than the stiffness threshold, set the target displacement level for the tip to the second displacement level associated with the potential tissue stiffness value corresponding to the determined tissue stiffness value, and adjust the AC drive signal output by the signal generator to the ultrasonic handpiece to achieve the set target displacement level. an ultrasonic handpiece comprising: a tip defining a lumen to provide suction at a surgical site, and a transducer coupled to the tip and configured to vibrate the tip responsive to receiving an AC drive signal; and a tip defining a lumen to provide suction at a surgical site, and a transducer coupled to the tip and configured to vibrate the tip responsive to receiving an AC drive signal; and a control console coupled to the ultrasonic handpiece, the control console comprising: a signal generator for generating the AC drive signal applied to the transducer, a sensor for measuring a voltage of the AC drive signal, a sensor for measuring a current of the AC drive signal, and a processor coupled to the sensors and the signal generator, a signal generator for generating the AC drive signal applied to the transducer, a sensor for measuring a voltage of the AC drive signal, a sensor for measuring a current of the AC drive signal, and a processor coupled to the sensors and the signal generator, determine a first displacement level for the tip that is a maximum displacement level for the tip, receive a tissue response model defining a stiffness threshold and second displacement levels for the tip that are each less than the first displacement level and associated within the tissue response model with a different potential tissue stiffness value greater than the stiffness threshold, determine a tissue stiffness value of tissue being contacted by the tip based on the measured voltage and current of the AC drive signal, determine whether the determined tissue stiffness value is less than the stiffness threshold, responsive to determining that the determined tissue stiffness value is less than the stiffness threshold, set a target displacement level for the tip to the first displacement level, responsive to determining that the determined tissue stiffness value is greater than the stiffness threshold, set the target displacement level for the tip to the second displacement level associated with the potential tissue stiffness value corresponding to the determined tissue stiffness value, and adjust the AC drive signal output by the signal generator to the ultrasonic handpiece to achieve the set target displacement level.