A few days sooner, I was improving a problem when corresponding with family by phones and video, with Skype system.
In fact, I was able to listen to what they were saying, but no sound in response appeared to be transmitted to them through my microphone.
A popup occured, telling there was a file missing:
DpvSetup.exe in RealTek drive, and it had to be reinstalled in managing Configuration Panel.
What I wasn't aware of: such a software is originally part of built-in material made by Acer and it could not be available wether in any Windows kit, nor in a downloaded program extracted from within the one or another Microsoft website.
Should anyone here be so kind to give a solution to that problem ?