My engine gets louder as more rpm I use. If I sleep in the Master Room, it makes a big differnce it the engine runs with 1200 -1300 rpm or over 1800 rpm. I will try to get some dB measures this season. I thougt it is normal, that it's getting louder. It's new for me, that it should be the same noise over the rpm range.
I have to check...