@Linkat,
My grandson, who lives with me along with both of his parents, is also a loud talker. At 5 years old, he gives no consideration to sleeping people (some of our family members work nights). I have noticed a genetic component to his vocal tone; although his mother (my dil) speaks softly) her dad has a booming voice and also seems blissfully unaware that his early morning visits to pick up his grandson are met at the door with sleepy, cranky people that don't appreciate repeated knocks while they gather robes and slippers. I don't know what to do, short of leaving the country. I've asked my son to get the kid's hearing tested, teach him some manners, take him to voice lessons, DO SOMETHING! I can't take it anymore! Help! It does put a strain on our relationship, and I certainly don't want that. He's a precious child, but he has no volume control.