Quotesudo 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.