The Wacko A/C system works on the principle of "bending the return airflow pathway" to quieten the "air rush noise". Essentially, it closes off the "air dump feature" so the device can be mounted under the ceiling unit. Air is drawn in from the rear, bends upward to enter the A/C plenum and then is cooled "by the original A/C system.
It's the "bending/re-routing" of the incoming air that's "muffled" by the Wacko addition.
Yes, it works, moderately well, if your A/C "noise" is the sound of air rushing into the return air vent. It won't quieten the vibrations above the roof that are typical of "steel stamped rafters". They still will be heard as the compressor kicks in and the fan blades vibrate....
For me, it works fairly well, but nearly $200 for a "box that screws under the air conditioner" ??? I'd think twice about whether the noise is "really that intrusive".... YMMV
2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS