We periodically "sound" test units with a decibel meter and can attest that portable oxygen concentrators ARE getting quieter. With that said, we understand that when you first take a unit out of the box (in the quiet of your home), they may seem louder than expected. This is particularly true if you have it at ear level sitting on the table with no other ambient noise.
Instead, try putting it in it’s case and over your shoulder and go for a walk or turn on the TV. You should notice that the noise begins to "disappear." While you may be self-conscious the first time you go to the movies or take the unit with you to church, you’ll notice it quickly "blends" in with other background noise.