Modern graphics processing units (GPUs) are massively parallel computing environments. They make it possible to run certain tasks orders of magnitude faster than what is possible with a central processing unit (CPU). One such case is simulation of room acoustics with wave-based modeling techniques. In this paper we show that it is possible to run room acoustic simulations with a finite-difference time-domain model in real-time for a modest-size geometry up to 7kHz sampling rate. For a 10% maximum dispersion error limit this means that our system can be used for realtime auralization up to 1.5kHz. In addition, the system is able to handle several simultaneous sound sources and a moving listener with no additional cost. The results of this study include performance comparison of different schemes showing that the interpolated wideband scheme is able to handle in real-time 1.4 times the bandwidth of the standard rectilinear scheme with the same maximum dispersion error.