Static noise coming from speakers

I Use ubuntu mate 14.04 on a new dell laptop, and noise that sounds like static comes from speakers after turning it on or rebooting. after a little while all sounds goes back to normal. this happen when i play music or i am on youtube or mumble

I have the same but it happened after my upgrade to 15.10 - did not have the noise issue present in 15.04. I also have a Dell laptop - Latitude E6540.
The noise is only present when no application is trying to play a sound. It will disappear when you move the volume slider (resulting in the ping noise) but will return after 10s of no sounds being played.
On board speakers are knackered so this is through the output jack.
4.2.0-17-generic kernel