I also am unclear on what form the harassment of your sister is taking.
I believe it is the neighbor that is harassing your sister with sound?
But if so, I am not sure what you mean to accomplish.
The most common and socially accepted rule is to have the volume go down during "quiet hours".
Of interest is a feature that Denon and Marantz AVR's have called LFC (low frequency containment). The point of this control is to allow reduction of the lower frequencies that would most likely be offensive to neighbors (or even people in the next room). I know when I play my system loud, the only thing I can hear outside (when doors and windows are closed) is the bass. This control gives me a way to be able to reduce that bass while playing the system loud.
PS-It has been my experience that there are not many features available on one AVR that don't soon show up on the other brands. Yamaha, Onkyo, Pioneer, and Sony may have an equivalent feature, but I am only familiar with Denon and Marantz.