If you can’t see the main menu, click the three rows of dots at the top left corner of the window, which displays as Show All in earlier versions of Mac OS X.
Alternatively, you can click on another sound input device from the device menu to use it as your main input device. You can test your input volume by monitoring the “Input Level” bar. Drag the “Input volume” slider above 0%, then clap your hands. You will see the input level bars turn grey as the internal mic picks up sound. Drag the slider back to 0%, and do the same test. You will not see any sound being picked up on the input level bars.
