Instead of making various wave files for different speeds, it would theoretically be easy to make different variations of sounds by changing the preset sampling rate in the WAV file.
Playing a 22KHz sound file at 44KHz would result in a faster, higher sound, i.e. a male voice sounding like a chipmunk's.
Application of feature? Create a music synthesizer. Revving up the engine of a car or other vehicle. Breaking down of a computer like it's running out of batteries. Giving variety to one certain sound effect so it doesn't sound repetitive throughout the game.