I once sat next to a guy at work whose phone would induce this noise in my speaker about 10 seconds before his phone actually rang. So one day just before his p

I once sat next to a guy at work whose phone would induce this noise in my speaker about 10 seconds before his phone actually rang. So one day just before his phone rang I said 'Steve, your wife's phoning' and a few seconds later, she was. He was totally freaked out by this; he'd never noticed the buzzing sound. He had no idea how I had worked this out. His wife rang him all the time, statistically it was pretty likely to be her. :-)