I posted this before, but:
My wife and I just moved into a brand new house this past July. There are definitely creaks and weird nosies from the house settling. However, I had a buddy over one night. We all had got a little drunk and as we were going to bed, my buddy jokingly knocks on our bedroom door and asks if he can sleep in our bed because "there is a ghost in his room!". "Go to bed Rodney!" I say.
The next day, after he went home, he told me his girlfriend asked him, "So, you called me last night?" He didn't remember calling her, so he checked his phone and there was no record of any new outgoing calls. He told her that he didn't call her, and she said, "That's interesting, because I had a missed call last night from you, and a voicemail. Listen to this." What came next was the weirdest thing ever.
It was this loud droning noise with lots of feedback and interferrance. Her phone would translate any voicemail into text, so while you heard this weird growling sound, the text message read, "HELP ME. HELP ME. ARE YOU THERE? HELP ME PLEASE!"