The work was aimed to develop a robust virtual sensing method for vibro-acoustic applications without the use of acoustic sensors. Sound pressures inside a vibro-acoustic enclosure were estimated from structural sensors by utilizing the effect of fluid-structural coupling. A structural sensor placement method was developed using the averaged sensor output energy of a vibro-acoustic system excited by a spatially-varying point source. It was found that the observability level of cavity-controlled mode is influenced by the modal coupling and resonance frequency of uncoupled structural modes. Robust filtering was used to develop virtual sensors that were robust against certain dynamic uncertainties in the vibroacoustic system. Virtual sensing performance was numerically investigated on a coupled panel-cavity system, which demonstrated superior sensing performance of robust virtual sensors compared to that of standard virtual sensors. Therefore the proposed virtual sensing method allows the use of compact structural sensors, instead of potentially bulky acoustic sensors, for sensing and active control applications of vibro-acoustic systems.