I like to think Robotnik has the angriest tones about the most mundane ideas. Angrily talking about dinner and Stone is just replying in a normal voice like, “Yes, dear, we can have garlic bread with the spaghetti tonight.” Bonus points if Robotnik is in some way actively snuggling with Stone.
I just love the idea that Robotnik has no idea how to express his emotions at a normal volume (Canon with the “OF COURSE I WANT A LATTE! I LOVE THE WAY YOU MAKE THEM.”). He didn’t bother to care about how loud he was being in the lab or the crab because Stone didn’t care and would never yell back. He also probably damaged his hearing with all the loud music and explosions (lab mishaps/the crash of the Death Egg) over the years so he thinks he is being quiet-ish.