Stressful environments will cause stress to baby. They can feel when there is tension or stress in their environment. A baby in a stressful environment is likely to cry more, and develop social and emotional problems later on. Keeping a peaceful environment will be most beneficial to the child now, and later on in life. When someone around the baby is yelling it puts stress on baby and scares them. They are trying to develop trust. The environment can affect that developmental process strongly.
So let people know when they come to the house to keep the volume down, do not fight in front of baby, and try to relax after being in a stressful situation, to avoid putting that stress on your baby, where it doesn't belong. There is no reason for the caregivers to fight over every little thing. Disagreements are possible without it turning into a yelling match. Trying to solve problems without getting stressed or yelling, will teach baby to do the same.