WHBM, I'm not so sure a mod is needed to be honest.
The PTU deals with the failure of an engine and it's associated engine driven pump. Subsequently it is running at 3000psi and having to shift alot of energy to pressurise the second system. The system is designed in such a way that the Hydraulic systems remain totally seperate from each other. PTU overheat can be a problem in the event of a leak as one side of the pump has no resistence due to no fluid braking effect and the driven side (i.e. the one with fluid in it) goes into overdrive and overheats the remaining system!!!! To be honest, in a situation requiring the use of the PTU in flight I would be a little more concerned about getting the aircraft down quickly than a large barking dog noise in the cabin!
The CFM 56 always sounded like a chainsaw! IAE changed the sound damping material in the engine intake to reduce the main fan noise on the v2500.
What is the situation for cabin pressurisation? Whilst taxiing or during climbout?........and why at that time?
I don't understand what you are asking? Hydraulics and pressurisation are totally seperate systems.