Optical holographic interferometry is used to study the vibrational characteristics of a sonar transducer. Experimental methods are described, and photographs of 13 resultant hologram images are included. Each is an interferometric fringe pattern from which the peak‐to‐peak amplitude of every point on the vibrating surface can be computed. The result of an exact theoretical analysis is stated; the solution for a simplified model is derived; and numerical results are compared.