Hi, I was wondering if anyone has experienced this odd phenomena also. I live right next to a private airport and at first thought it may be a plane but at 2 am last night I went to let my dog out to use the bathroom when I began hearing this low frequency humming. I noticed my dog was really intent at staring at the sky, I kept yelling for her to come back in when the frequency got louder and louder and she wouldn't stop looking up. I was too afraid to go actually look to see what it was. But it sounded unlike any plane I have ever heard. I found it very peculiar and have been looking online to see if I can find anything mimicking the noise I heard with not much luck. Is their some natural explanation for this?