I have a few USB inputs on my Macbook Pro. I have noticed that the the Mute Microphone works while I have the Internal Microphone set as my input device, but it will not mute the microphone if I have one of my USB inputs set as the input device. For example, the picture below shows that sound is still getting through even though the input volume is set to the lowest setting by selecting Mute Microphone. It doesn't appear to work correctly.
Is there a way that I can set the Mute Microphone to mute all microphones?

Is there a way that I can set the Mute Microphone to mute all microphones?
