Injection molding is the most important process to produce plastic parts. Because of increasing complexity of the plastic parts and the aim to reach zero-defect production it is a must to control the dynamic injection molding process. Therefore information from the inside of the mold, measured with sensors, is necessary. State of the art is to implement wired mold cavity pressure sensors as well as wired cavity temperature sensors. This article presents a novel wireless measurement setup which uses structure borne sound as transport medium. The sound is generated by an acoustic actor which is activated by the passing flow front at certain predetermined positions in the cavity (or cavities). Beside the mechanical setup of the sensor proof of concept measurements with a prototype setup are shown in this article. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013