Notebook Audio

Hi all, 

this is literally doing my head in.

So for a few months I noticed that the sound was playing up a bit on my laptop - so when I played videos it first started at a certain sound level and then changed tone after a few seconds - this did not bother me too much as the volume level more or less stayed the same.

But for about 6-7 weeks I noticed this crackling or static sound coming from my speakers even when I mute them or plug in headphones. It also happens on start up. 

I have re-installed the drivers but to know avail. I also de-installed any updates that may have caused this but it persists.

Now I did notice that it seems to be connected to my "pop up" messages - e.g when I get a message on the right of my screen that there may be a new e-mail or just general pop ups that usually come with a tone...

I also noticed that disabling the Realtek speakers completely makes it go away - but then of course I have no sound at all so that only helps temporarily when I want some peace and quiet. 

I downloaded the HP Hardware Diagnostics tool but it said audio devices are working properly. The normal troubleshooter says the same.

I am not hugely technically gifted so a simple solution would be perfect without having to go itno too much geeky stuff - however if it is described to me in a step by step manner I can follow instructions:-) 

Thanks heaps in advance for any help!