Mic level change (what appears to be an "auto" adjustment) solution in detail:
After doing some research and experimenting on this, what is happening on my system is each time VA is started, closed, or any of its features clicked, the Speech Recognition module is triggered and results in the module resetting the microphone volume to that set by the MICROPHONE VOLUME WIZARD.
The reason I point this out here is it have been stated elsewhere the volume is set by the recognition TRAINING.
So to be clear it's not the actual speech dictation training which does this. The mic volume wizard is a separate module available for Win7 in Control Panel->Speech Recognition->Set up Microphone (your OS may vary a bit.)
In the same OS, users have manual control over the mic level in:
Control Panel->Sound->Recording->Microphone->Properties->Levels.
The problem:
When running the wizard on modern headsets with quality microphones, the wizard is too sensitive and sets the volume too low. SR (Speech Recognition) then misses the subtle nuances of word portions. Many users like myself will go into the manual mic volume and increase it to levels which also work well with other voice applications like TeamSpeak and Discord. With the checkbox selected to listen to the mic, the best approach is to raise it so most indications on the volume display meter graphic reach half way or more and while listening to stronger pronounced words with sharp consonants, there are no clipping distortions at the peaks. After going though all this and getting the mic JUST RIGHT, VA/SR will reset back to the former wizard volume. Ugh.
The SOLUTION:
Display the mic volume setting screen as described for manually setting the volume.
Run the mic level wizard (not the dictation training): Control Panel->Speech Recognition->Set up Microphone.
This time while the wiz is running, move the microphone further away than is normal and use a lower spoken energy than normal. Keep working with the wizard until you see it set the level to the good manual volume NUMBER you KNOW works well with VA and all your voice connections. Now exit the wizard and the mic controls.
DONE:
For now on, VA/Speech Recognition will set the mic level to the ideal setting you want which SHOULD mean it doesn't move if you followed the procedure above.
-Pv-