I’ve been looking at this product, but haven’t pulled the trigger yet...kind of pricey for what you get:
Basically, this device seems to close off the cold/conditioned air dump, forcing the conditioned air out through all the small round vents. I may try a version of this myself, once the weather getts warm enough here to actually test it.
Looking at my AC unit (Dometic), the fan is positioned just above the cold air dump, about 4 inches from the opening, so no wonder it is noisy! The Wacko AC Silencer closes off the cold air dump with foil tape, and adds a layer of sound deadening material...should be easy enough to try, and totally reversible if I don’t like the result!
BTW, as others have pointed out, many RV AC units lose efficiency because the warm air return is not completely separated from the cold air dump (in my case, a too small piece of metal and a strip of foam tape, with multiple gaps and leaks!). This lack of separation allows conditioned air to mix with unconditioned air, reducing cooling efficiency. I remedied mine with foil tape and a double wall of half inch closed cell foam.
First photo shows my unit with just air filter removed...red arrow is the unconditioned air return, green arrow is the cold air dump, yellow arrow is the piece of foam tape they slapped into place to try to separate the two.
Next photo shows the too short piece of metal under the tape.
3rd photo shows the view up inside the cold air dump, where you can see the fan, as well as one of the foam walls I have started to tape into place.
4th photo shows the foam wall taped from the other side, and the metal shield reinstalled.
5th photo shows a second layer of half inch closed cell foam taped into place over the metal shield.
I also discovered that the round air vents are mounted over “ducts” built out of styrofoam, and as others have others have pointed out, these channels are open-ended, allowing precious cooled air to be wasted by dumping into the fiberglass cap in front, and into the ceiling over the bed in the rear of my 23TR. I used the same closed cell foam to make end-walls just beyond the vents closest to the front and the rear of the rig.
Just taking these steps made a big difference in the amount of air coming out of the small round vents! Hoping that will help improve cooling efficiency too.