Implantable medical devices including an ultrasonic transducer and methods of optimizing an ultrasonic transducer of an implantable medical device are disclosed. The implantable medical device can include a housing, an ultrasonic transducer disposed within an interior of the housing, and a limiting structure configured to constrain deformation of the ultrasonic transducer. The limiting structure can include a separate structure coupled to the housing, or can comprise a resonant portion of the housing itself. During operation, the ultrasonic transducer is configured to communicate at a frequency at or near a resonant frequency of the housing.