An apparatus includes a body, a shaft assembly, an end effector, a first acoustic sensor, and a processor. The shaft assembly extends distally from the body. The end effector is located at the distal end of the shaft assembly. The end effector is operable to apply energy to tissue and thereby change a state of the tissue. The first acoustic sensor is configured to pick up sound emitted by tissue. The processor is in communication with the first acoustic sensor. The processor is configured to provide an automated response in response to a signal from the first acoustic sensor indicating a change in the state of the tissue.