Variable Playback Speed?

Hi all,

I may have over-looked this in the documentation, but I don't see any way to change the playback speed of a sound sample (openAL). I'd like to have my car engine speed up / slow down, as the car accelerates and decelerates. I think changing the playback rate of the engine sound would be the perfect way to accomplish this.

Is it possible? or other suggestions to accomplish the same effect?