[ Solved ] Linux - Logitech webcam microphone not working in skype.

sudo apt-get install audacity

Go to Edit

then Preferences

then Devices

then choose " Recording " option and select the input microphone mic device

and record audio and play to check if mic is working.

Then go to sound settings and select "INPUT" tab.

And, select the logitech webcam microphone as "Set as fallback" unselect other cards... select the single correct option.

Now mic works on skype.