Platform: HP Zbook 15 G2. Under Scientific Linux 7 , the onboard microphone system, web camera, and speaker system worked. Under 20.04.1 LTS, the web camera and speaker systems work (tested by VLC Media -> open capture device) work, but the microphone produces nothing but static. An external USB microphone works fine. I have installed Pulse Audio Volume Control and alsamixer that both "work" but do not allow me to fix the issue. The microphones physically are located near the web camera in the top front bezel of the flat screen display lid and thus isolated from (most) internal noises of the fan(s), etc. I will post additional details if there are specific requests. I have followed the instructions in https://linuxconfig.org/how-to-test-microphone-on-ubuntu-20-04-focal-fossa#:~:text=How%20to%20test%20microphone%20on%20Ubuntu%2020.04%20step,device%20and%20start%20speaking%20to%20the%20selected%20microphone.
and related web sites, but to no avail. There are two audio boards on the machine, but only the Intel one seems to be active and I cannot find out how to activate the other (that may not be appropriate as I recall that SL 7 used the Intel board). Take care. Stay safe.
Static pulsing sound produced from internal microphones
solves the problem for now -- I will update if other issues appear. I use vlc in the mode that it displays the onboard web cam and the onboard microphone in vlc so that one may observe, with a delay, what should be recorded, shown in zoom, etc. I made the script in the above URL (that displays as a text link, not the actual URL starting with https) into an executable sh script and put the pulseaudio commands in the URL into my script. Should I post the final working script in this answer? Take care. Stay safe.