7100 Microphone issue has a solution to fix
 

I have BlackBerry 7100, but I could not talk to any mobile phones 4 months ago because receiver could not hear any my voice, they only heard a noise like a wind tunnel. However, if it was connected to a normal telephone (not mobile phone) then this issue did not happen. I have raised this issue but there was no any solution to fix this issue.
I just have discovered and I think I found the root cause of this issue, it did not come from microphone as I thought, it is problem of network selection when the signal was generated from my device.

How to fix:
If you have the same problem, please check your device Network again, you should set your Network as follows: at item "Network Selection Mode", you choose "Manual" instead of "Automatic", then you will select specific your network.
I tried this selection many times through last week and now I am feeling it is OK.
Hopefully, you will be successful!

Thanks for posting you findings, I will give it a try later today.