the housing of a rotary ball type industrial vibrator is injection molded from a reinforced plastic material , and an annular metal raceway structure is molded integrally with the housing and forms a contact surface for a metal ball disposed within the interior of the housing . in response to a flow of pressurized air through the housing , the ball is rapidly rotated around the metal raceway to impart oscillating vibrational forces which are transmitted through the housing to a bulk material handling structure to which it is rigidly secured . the light weight plastic housing facilitates a highly efficient vibrational force transfer to the material handling structure , and the integrally molded metal raceway structure isolates the rotating ball from the interior plastic housing surface to prevent internal housing abrasion , and significantly reduces operational noise generation .