Thanks to everyone for the replies.
Interested in the Wackoproducts item so took a look at their site (thanks for the link).
Funny thing, they promise an 8-10 decibel reduction in noise (although initially, on the main page, they only promise a noise reduction, one has to hunt a bit for the 8-10), however, they also link an installation and review video in which the guy uses both a decibel meter and a db app on his cell phone. Both show a before/after comparison of about 2 decibel difference. 2 db is quite a bit different than 8-10.
As we have Dometic ducted a/c, will have to give this product further thought.
Marv