Noise control is almost always a more accurate description than soundproof because nothing can be made entirely sound proof in a home. Low frequencies deform almost any structure and will pass through almost any material.
Its true that we may not notice loud noises in another part of the house. What if the noise gets even louder and it's late at night? Daytime noises that might have masked other sounds is gone. We can control how much noise moves from one place to another.
I help architects, builders and home owners reduce noise that comes from neighbors, HVAC systems, home theaters, traffic, garage bands or almost any other residential issue.