Why every time i have voice chat with my nephew, the program somehow gets into my Windows soud settings configuration and lowers my microphone's potency?

It has to be at 100% to be heard pretty well, and every time i use Steam voice chat to play with my nephew, it lowers it to 85% or so, which makes it nearly unhearable, which is a problem to me since i use it to record Let's Plays on YouTube, so every time i play with my nephew, i have to remember to raise it to 100% back again before recording.

Is there ANY way to solve that? It also happens amidst playing with him, he tells me that i sound so low so i also have to raise it again while i play with him.

I don't use Push-to-play or anything.