Making a.sound...what is causing it?

I have crack my screen like a two weeks ago and ive notice the last couple of days my phone starts makin a sound sometimes longer then others..i.cant tell wether it is the screen or my speaker or batterie..but Ihardly watch videos and it dont do it when I get a call..is this normal with a cracked screen? my replacement screen.wont.be.here.until next month