Digital games are based on interactive virtual environments where graphics and audio are combined. In many of these games there is lot of effort put into graphics while leaving the audio part underdeveloped. Audio in games is important in order to immerse the player in the virtual environment. Where a high level of emulated reality is needed graphics and audio should be combined on a similar level of realism. To make this possible a sophisticated method for audio simulation is needed. In the audio simulation field previous attempts at using ray tracing methods were successful. With methods based on ray tracing the sound waves are traced from the audio source to the listener in the virtual environment, where the environment is based on a scene consisting of implicit surfaces. A key part in the tracing computations is finding the intersection point between a sound wave and the surfaces in the scene. Sphere tracing is an alternative method for finding the intersection point and has been shown to be feasible for real-time usage on the graphics processing unit (GPU). To be interactive a game environment runs in real-time, this fact puts a time constraint on the rendering of the graphics and audio. The time constraint is based on the time window to render one frame in the synchronized rendering of graphics and audio based on the frame rate of the graphics. Consumer computer systems of today are in general equipped with a GPU, if an audio simulation can use the GPU in real-time this is a possible implementation target in a game system. The aim of this thesis is to investigate if audio simulation with the ray tracing method based on sphere tracing is possible to run in real-time on the GPU. An audio simulation system is implemented in order to examine the possibility for real-time usage based on computation time. The results of this thesis show that audio simulation with implicit surfaces using sphere tracing is possible to use in real-time with the GPU in some form. The time consumption for an audio simulation system like this is small enough to enable it for real-time usage. Based on an interactive graphics frame rate the time consumption allows the graphics and audio computations to use the GPU in the same frame time.