Not a normal blog post but I have had great difficulty on occasion finding solutions to my Ubuntu problems (although it was much harder as a novice ten years ago with dial up and command-line only slackware, of course). So should anyone else have the same problem, how to get the built in mic working on an Acer Aspire laptop, they may google and find this.
Might not work for them, but even so. I've seen plenty of other explanations, but none of them worked for me.
Open Volume Control, which should be a speaker icon in the top taskbar, click preferences, tick any unticked boxes with "recording" or "options" next to them, which in my case means having three under recording and two "input"s under options. Next, as some of the other fixes state, increase volume on "capture" and "capture 1" under the recording tab (which should have appeared by now) but if you put both to max expect inexplicable white noise, so don't. Click, if necessary, the little mics next to the speakers below the sliders so they don't have the little red crosses on them. You'll have to do this, it would seem, every time you want to record something, I haven't found out how to avoid that yet. Finally there are two options under "options", both labelled input. with the options "mic" and "front mic". Make the top one front mic and the bottom one mic, if you do it the other way around it squeals.
Should do it. Might not.