I wasn’t intending to contradict you - sorry if I came off that way - this is just what traceable open-sources say - and thought you’d be interested. In engineering terms 30 vs 50 (just a few dB among friends!) isn’t that significant, and doesn’t alter the remediation requirement or methods if you are concerned with the threat.
You didn’t come off as abrasive at all - I took it more along the lines of - Great - someone actually confirming what I remember. You also explained the results of a story I heard in Engineering school 30+ years ago!
That was about the only thing I remember from AC Machines class!