$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: SB [HDA ATI SB], device 0: ALC887-VD Analog [ALC887-VD Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: SB [HDA ATI SB], device 2: ALC887-VD Analog [ALC887-VD Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
Try the following command in a terminal
arecord -D hw:0,0 -f cd -d 10 > ~/test.wavThat will record a file /home/<username>/test.wav
It will stop recording after 10 secs ........ -d 10
It will have the preset file format CD ...... f cd
It will record from the hardware at location 0,0 ........ hw:0,0
To play back that file, while still using the terminal do
aplay ~/test.wavIf the MIC is turned down completely or muted you will get silence ...... or if the hardware specified is incorrect you will also get silence.
hw:0,0 ..... the first zero is the card number which is correct and the second zero is the device on the card ..... if there are several inputs such as front & rear MICs and line in, for instance, then you might have to alter the second zero to correspond to the input you are using, like this ....
arecord -D hw:0,1 -f cd -d 10 > ~/test.wavI much prefer to use PulseAudio, as is obvious from my posts on the forum

, as it gives a GUI method to select the input, the input 'volume' as well as the output and its volume.
While recording the input can be changed 'on the fly' and there is an indicator showing the input level so you can be sure it is recording some sound and not silence.
All those are available through PulseAudio Volume control (pavucontrol from the repository).
Anyway try without PulseAudio first and see if you can record something.