My air conditioning was emitting a strange, hard to hear whistling sound recently. If I was watching TV or doing other things, I could not hear it, but when I was trying to sleep it was a distraction. The whistling noise only powered up when the air conditioning was on. It wasn’t consistent, making this even more annoying because if it was, I’d learn to tune it out. It was making me think I was crazy! No one else in my family could hear it! But I have not been getting good sleep in over a week, so I decided to call up our air conditioner company. The technician came out and readjusted the little door that closes the air filter. The whistling sound stopped! Apparently, my husband had not closed the little door when he changed the filter last week. Air escaping through the little gap in the door was the cause. I am glad it was such a self-explanatory fix but I wish I had thought of this myself; it would have saved money! At least I know I wasn’t crazy, though – that the sound existed even if no one else could hear it. I hope I sleep well tonight. I bet I will, since the sound is gone.