The results of laboratory experiments designed to characterize the underwater sound field radiated by a breaking wave are presented. Two general types of experiments were performed. First, progressive gravity waves were produced in a flume tank (2×2×12 ft; 7×7×6 ft) by a plunger wavemaker (wedge‐shaped) at one end of the flume. Near the other end was placed an airfoil with a given angle of attack forcing gravity waves to break in the tank region. The second series of experiments involved the introduction of a jet of water, simulating a plunging breaker, onto the plane water surface of the tank. The water jet was produced by releasing a fixed volume of water, held in a cylindrical container, onto the surface. The jet characteristics were varied by changing the container's volume and height. The hydrodynamic characteristics of the bubble plumes generated by these two mechanisms were measured by using a high‐speed video camera. The underwater acoustic emissions from these air entrainment processes were recorded simultaneously with the high‐speed video camera and a digital oscilloscope that possessed a large memory. Concurrent video image, power spectrum, and observed time evolution of the bubble plumes generated by these two mechanisms reveal a dominant acoustic signal occurring at frequencies lower than 200 Hz. [Work supported by ONT.]