I don't own a fan, so I used a youtube video of a fan. 100%
Put your Xbox mic in front of the your PC/phone speakers playing this youtube video, and be amazed as by this fan's American Idol performance.
Put the songs on easy, mute your xbox, and let the fan noise impress your dimwitted microphone. If you're having trouble, just turn the volume up for the fan.
Note: I wish I was joking, but I'm not.