The buzzing

At my dads house (which I no longer go to due to some problems with him) I always would here the iPhone message buzzing thing I could never locate where exactly it was. At one point it would sound louder in one area then the next second it would sound louder somewhere else. This was only ever in my room from what I know. It would happen when my phone was dead even when no one else was home.

It always freaked me out, can anyone just help me figure it out?