Guys I've found a solution to this problem.
I recently installed arma 3 and noticed that my friends could barely hear me, even though I have the in game config Mic sensitivity maxed out.
The issue should be with steam. In the steam menu, click on 'steam' in the upper left. Then select settings. Go down to the voice tab. Under voice, you should see an option to 'Boost Microphone Gain'. You can test your mic now and you should be able to hear your own voice.
Hope this helped!