I use Lenovo P70 as my Ubuntu workstation and most of the time I am reasonably ok with it. However, join a call and my microphone is either too low or there is way too much background noise. And that's whether I use internal microphone or headset.
I tried playing with the slider but that's annoying beyond belief. Sweet spot seems to be in bottom fifth but there is a really fine line between making background noise stop and my voice inaudible. Since there is no numerical value next to slider, eyeing out the perfect level is close to impossible.
As it often happens in Linux, solution comes courtesy of command line.
amixer set Capture 80%
I found that 80% level is where background noise becomes drastically less noticeable while still allowing my voice to come through.
PS: Interestingly, 100% level from command line puts slider at 1/5th of the sale. That means that (over)amplification can get up to 500%. A bit much...