Abstract
Theoretical considerations have been performed for obtaining the energy density of the incident ultrasonic beam by measuring the acoustic radiation pressure on large objects in comparison to the wave-length of sound. Experiment has been performed by employing a balance-type radiometer and by employing spheres, cones of vertex angles of 60°, 90° and 120°, and plane discs made of different materials --- iron, brass, duralmin, bakelite and polystyrene --- as objects for measuring the radiation pressure. It has been observed that the spheres give constant and common values of the radiation pressure irrespective of the materials, and that they are satisfactory for absolute measurements. Iron and brass cones with vertex angle of 90° have given good results, too.
