Microphone crackling in Ubuntu 12.04

Solution 1:

I had the same issue. Try installing alsa-mixer and by using it try to mute one channel of the input (either left or right).

Solution 2:

Try and see if the same mic has the same problems on a different computer.

If the sound is still there then get a new mic.

If not then try and see if there is some dirt or other junk in the port.

If there is no junk in the port and there is still a problem then see if there is a loose connection on the inside of the computer. If you use the mic port a lot then it is most likely crack from the motherboard (it is easy to do this unfortunately).