Audio Control Panel Settings for
Microphone Recording on a Macintosh

To check your settings, pull down under the blue Apple icon in the upper left of your screen to System Preferences. In the second row, click the icon for Sound

Click the tab for Input and make sure the settings are as illustrated below. In particular, check that the input is from the internal microphone and that when you speak to the screen the volume meter responds. When done, close this window (you don't need to Quit this as you should with all other programs.)