Disable internal microphone

Hi,

I have an Android car unit that has both an internal microphone - and a 3,5mm mini jack connector for external microphone. Unfortunately the internal microphone does a very bad job and I would like to use an external higher quality microphone, but when I connect one the audio input becomes even worse than before. I contacted the car unit producer and they told me I had to open the unit and cut the wire to the internal microphone. If you add an external microphone you get input from both microphones at the same time (I can confirm this to be true) instead of only input from the external one. The internal one is supposed to do some noise canceling i guess, but it makes it worse.

Question is: can this program be used to disable the internal microphone - while leaving the external one as is?