When opening smartCARS, you receive an error box stating that there was an error initializing the XAudio2 sound engine and your smartCARS sounds do not work.
This can be resolved by installing or repairing DirectX with this file.
A specific version of the DirectX libraries are required to run smartCARS. In some cases, a system has DirectX, but not the right version. Repairing it with the above executable ensures that the DirectX libraries smartCARS needs are present.