A degreased is sometimes helpful to cut through thick tar/nicotine buildup. 

Just adding thickness won't block the entire listening frequency spectrum, surface textures can help too, look to studio construction, it should explain the frequency ranges and standards as well as textures in design.....find an audio engineer.Why not ask the neighbor not to put the dog along that wall.

I would consider maybe a rubber apron of some sort or really thick cloth.

Brick can be laid up thousands of ways and thicknesses depending on the aesthetics or structural demands of the home/building.

Believe it or not, you kind of need a thick skin to do this because you’re going to hear all kinds of stuff, some of it critical, some of it positive, and some of it a little nuts or pretty far from objective.

You need thick skin to be a landlord.

Over in the next county the magistrate makes evicting LLs present their whole case EVEN WHEN THE EVICTEE IS A NO SHOW.When I appear I pull out a thick folder stuffed with papers making it look like I'm loaded for bear and prepared for anything.Also, make sure your cell phone is off, here in this county the sheriff will confiscate offending phones.I've been to court where the other side's father actually hired an attorney.

Sorry James, but I have thick skin and I know who I am and what I'm about.

Caked on an inch thick. 

When you have the 1st & 2nd floor exterior walls insulated you need insulation between them in the floor joist area only along the perimeter and it only has to come in as far as the thickness of the framed walls.