Problem with my A4Tech view cam with bui...

Make sure that you select the correct source for the voice or recording in the Windows sound settings (control panel).
If multiple audio solutions are installed, the default is mostly the sound card input. You need to select the microphone from the webcam.

More generic Webcam troubleshooting:
http://www.pcauthorities.com/pc-errors/how-to-fix-webcam-problems

Jules