None of the Compressors are quiet. Just some are less loud than others. I use the Ombra and it is "less loud" than the first compressor I used and it is a workhorse.

A bit of information: Airway clearance does take time, requires persistence and patience. I'm certain others would agree that it is frustrating the amount of time spent with doing it. However, the payoff with clearer airways, less infections and complications is worth it for a better quality of life.