My laptop has a built-in microphone, and I also have an external (plugin) microphone. I'm running Kubuntu. How can I test if the microphone is working and adjust its sensitivity?

I've tried making a Skype sound-test call and hear nothing when I speak into the mike. The best kind of test, I'd think, would be to directly record a short segment of speech and play it back, but I don't know how to do that outside of Skype. The relevant line from lspci (I think) is:

00:14.2 Audio device: ATI Technologies Inc IXP SB4x0 High Definition Audio Controller (rev 01)

When I test a microphone I either use audacity or arecord.

Audacity is the simple GUI tool - press the record button and check for input.

arecord is command line - handy for quickly specifying a device and settings.

The kde mixer can adjust sensitivity. So can alsamixer.

I don't know if kubuntu has all of the above, but they should be easy to find and install.