Open up your Control Panel -> Sounds -> Recording Devices -> Double Click your Microphone -> Advanced -> uncheck the box that says 'Allow applications to take exclusive control of this device'. -> Apply
I think you have some program that works with your mic in some kind of way. And if you have one. try uninstalling it. It might be a thing for teamspeak, or skype, or just a normal voice changer or something like that
Sometimes games change it, for a while everytime I started Black Ops 3 my mic would go low but now its fine, when I play anything on the uplay app it changes my mic volume too
Sometimes games change it, for a while everytime I started Black Ops 3 my mic would go low but now its fine, when I play anything on the uplay app it changes my mic volume too