Most heating systems dry the air in your bedroom, so borrow a humidifier to see if it will help. Keeping heat down and having a window open can also keep humidity up. For others, noise can interrupt sleep. In addition to the fan strategy, try particular kinds of music to blot out the noise. Play a recording of music that has no words, no definite melody, and not a lot of change in the volume.
Baroque music is a good choice.
There are many tapes of sounds that aid sleep by quieting the mind, emotions, and body. Check at the counseling center, at a mental health center, or holistic health center. If desperate, you might try ear plugs that workers use on noisy jobs. If you use cotton, be sure to use balls large enough that they won ' t work down into your ear canal and have to be removed by a physician. Focusing on insomnia might make it worse.