Randall, that is exactly the way our is and with the surrounds sound you have to turn it up so far the entire camp ground hears it. There has to be an alternative to this, just need to find it.
For the most part...it's strictly an airflow issue. X amount of air flowing through Y sized air plenum. There's friction between the air and the plenum and the outlets.
I have had 2 motorhome from 2 different manufacturers that were ducted....still had airflow noise. Just as much as the PC when it runs on high fan. The big difference on those motorhomes is the theromostat allowed either high or low fan speed with auto fan. I kept them on low speed and the fan only came on when needed.
The newer Dometic units allow only always on high, always on low or Auto where the unit decides if high or low but does turn off.
Until Dometic gives us the option of AutoHi, AutoLo, AlwaysHi and AlwaysLow...we're stuck.
But in any event...air conditioners in "small rooms" will always be somewhat noisy.