Getting a weird phone call every night

It just happened again. For the past week or so, around the same time, the home phone rings. We screen our calls, so I don't answer it until the voicemail kicks in.  There's only a very loud, grating, grinding buzzing heavy machinery sound, then they hang up.  It's almost like a fax machine call, but we have no fax machine.  The caller ID just says "out of area". Anyone know what this could be?

(NOTE: NOT like a fax machine. Been a long time since I've heard one; looked it up online--doesn't sound like it)

We used to get collector calls that would grab the first live person that answered the phone.  Have you called the phone company?  I have gotten calls lately that I have won a cruise.  Yeah ok.  

Robocalls..........some kind of scam no doubt.

I'm thinking robocalls, too.

FWIW, you can have your phone line monitored and it doesn't cost anything (at least it didn't used to). We were getting some funky calls several years ago, so we called the phone company. We had to also call the police. The police came to the house, took down the information. In order for our line to be tapped, we had to sign papers stating that we would press charges on the caller.......regardless of who it was (it could have been my mother, our son, it didn't matter; we had to press charges) and then the company put the tap on our phone line. It was on for two months.

I also think robo calls I get them and often get these weird sounds