US Patent 7987718 Vibroacoustic system for vibration testing

Forces are applied to a device under test and its mechanical response is measured by a laser vibrometer (50). The forces are applied without making physical contact with the device by producing an acoustical force with an ultrasonic beam (54). One embodiment employs two confocal transducers (56, 58) that produce beams that flood the device. Drive signals modulate the ultrasonic beams to produce the desired forces, and the use on a plurality of ultrasonic beams enable selective excitation of different modes of vibration of the object (7).