@JackE ...i disabled fast startup and unfortunately it has made no difference.  So, as it stands, the only relief i get from the grating static sound is if i alter the 16 bit setting every time i log in, even then it still occurs when i lift the lid of my laptop, when entering my pin number, and when i sign out. I suppose this is the best i'm going to get.  Thank you for your time and patience.  Still extremely disappointed with Acer, as i said when i have the time and energy i will ring them again, far too stressful.

@JackE ...not this particular machine, this is a replacement for exact same model which did go in for repair of this issue to Acer Store UK where i purchased it from, the issue was identified but not diagnosed, i was told that i would receive an update to help in dealing with the problem, so emailed Acer Store UK but they haven't replied.