My Realtek High Definition Audio microphone isn't working.

Hi,

1.       Was it working fine earlier?

2.       Have you made any changes to the computer prior to this issue?

The following are some of the reasons that may cause this type of issues:

1. The microphone may not be close enough to pick up your voice. Make sure that the microphone is positioned close enough and that you are speaking directly into it.

2. The microphone is muted. Some microphones have an external control for muting. Make sure the mute control is turned off.

3. The microphone input level is too low. Make sure that the microphone input level is set properly.

To adjust the microphone input level

a. Open Audio Devices and Sound Themes by clicking the Start button , clicking Control Panel, clicking Hardware and Sound, and then clicking Sound.
b. Click the Recording tab.
c. Double-click the microphone that you use for Speech Recognition.
d. Click the Levels tab, and then use the slider to set the input level for your microphone.

4. The microphone connections are not properly attached. Make sure the microphone wires are intact and unbroken. The connections to the computer might be loose, so unplug the wires and reconnect them, making sure they fit snugly.

5. A different microphone is selected for use with Speech Recognition. If you have more than one microphone installed on your computer, the wrong one might be selected for use with Speech Recognition. Make sure that you're using the microphone selected for Speech Recognition.

To change which microphone is used with Speech Recognition

a. Open Audio Devices and Sound Themes by clicking the Start button , clicking Control Panel, clicking Hardware and Sound, and then clicking Sound. 
b. Click the Recording tab.
c. Select the microphone that you want to use with Speech Recognition, and then click Set Default.


For more information visit http://windows.microsoft.com/en-us/windows-vista/Troubleshoot-Speech-Recognition-problems
 
Hope this information is helpful.