Why is My Microphone So quiet When I talk

Hi Everyone My Name is Keshawn and I have the iMac Mid 2007 20’’ inch with the 2GHz core 2 Duo Processor.my issue is my Microphone is so quiet.When I talk in a Normal Voice it sounds like I am Whispering.When I yell or scream it sounds like I am talking normally but it so unclear.All the settings are on high.I even turned off ambient sound and it makes it a bit loud but not much.I tried Resetting Nvram Didnt help.Reinstalled Mac OS X El Capitan 3 times didn’t Help.Even tried another os and didn’t help either.I Know its not broken physically cuz I can hear myself. Is there dust and debris blocking the microphone?Any Suggestions??

So this is my Microphone when I am Talking normally and the Settings and configurations.