In an injection molding process, it can be difficult to detect, in real time, process control variables such as pressure and temperature. Traditional temperature detectors and pressure sensors can be difficult to place in or near a mold cavity. An example embodiment of the present invention includes a self-powered multivariate sensor and uses acoustic transmission. The sensor may employ an infra-red thermal detector and pressure sensor and transmit coded representations of measurements acoustically via a body of the mold. From the temperature and pressure, melt velocity and melt viscosity of a compound in the mold can be determined with a high degree of accuracy by a processor internal to or external from the sensor. The example embodiment maintains structural integrity of the mold, provides a wireless self-powered sensor, and makes available sensing of properties of the viscous compound to enable injection molded parts production at a success rate exceeding 90%.