Hi, My name is Daniel and I am the founder of Galactic Games. I also struggled with this problem and found a partial solution.
If you want to change the microphone volume, use the command: voice.SilenceDetectionThreshold from 0.08 to 0.
To change the microphone sensitivity use the command: voice.MicNoiseGateThreshold from 0.08 to 0.
I personally liked the 0.001 value for voice.SilenceDetectionThreshold and voice.MicNoiseGateThreshold but it depends on the player so I recommend using a slider with 0 to 0.04.
You use the command with the execute command.