Try enable Mic Boost.
1. Control Panel -> Sound and Audio Devices Properties -> Advanced, this will bring up the Volume Control.
2. Go to Options -> Properties, change Mixer Device from Realtek HD Audio Output to Realtek HD Audio Input, and then click on OK to close.
3. Go to Options -> Advanced. Once Advanced is checked, then click on Advanced Button below the Mic slider control. Check the Mic Boost box.
4. Make sure Mic volume is also all the way up.
It should look similar like the image below.