A controller for a surgical navigation system is presented. The controller is configured to receive a position signal from a tracking system, wherein the position signal is indicative of a position of a hand-held surgical device that is tracked by the surgical navigation system inside an operation environment. The controller is further configured to receive sound signals from a plurality of microphones directed toward the operation environment, wherein the sound signals potentially contain one or more voice commands from one or more voice sources inside the operation environment. The controller is configured to process the sound signals dependent on the position signal.