Some people are overly conscientious of people around them, and ask questions like these even though they are already being completely reasonable. It's a huge jump to assume they must be being an asshole, yelling into their mic etc. Try asking next time: "are you concerned about it because you tend to get excited and loud while chatting? Or is it more just a normal phone-call conversation volume?"
My question is coming more from the perspective of, "i think i'd like to try voice chatting but i really don't want to be thatroommate someone wants to strangle"
Have you considered talking to your roommates about it? Maybe let them know that you want to make sure you're not disturbing them and asking them to send you a text or knock on your door if it's too loud? They might have ideas on how to minimize the sounds and/or agree on "quiet hours".
C'mon, even we had one of those giant long phone cords so you could answer the phone in the kitchen and stretch it around into the other room so you could talk with your friend without your mom overhearing everything.