I was capturing audio in Asterisk and playing it for a good reason: I noticed a while ago that attempts were made to route sip calls through an asterisk server I set up. Calls to numbers which looked valid. So they were probably attempts to make calls on 'my dime'. Which wasn't going to happen.
What better (on a server which has absolutely no credentials available to incur call costs anyway) to do with these than 'play' with these attempts a bit. I decided to answer the call with a random choice of the International Telephone Sounds & Recordings from telephone world and record the audio. I was hoping to hear someone be enthusiast in the background about their attempt maybe going through.
But in all the attempts I never heard anything more than the audio from the local end and maybe some echo.