My Internal Microphone can't detect my voice.

I used to use GarageBand to record vocally but a couple months ago it couldn't detect my voice so I went to System Preferences > Sound

and in the Input Tab, in the Internal Microphone both Input and Output Volume are set to max and unmuted. If i speak into the microphone it can't detect my voice but if i clap or whistle loudly into it it can detect it and so does GarageBand. I don't know if it is something I can fix myself or I have to bring it in the store to fix. Any help would be greatly appreciated.