Just for reference I propped up the rear end of my Aventure just to see what the motor itself at full RPM put out for DB with a real meter, and I came up with 50.12db at 3 feet, 56.8db at one foot, which I'd rank as "acceptable" for the claimed <=55db that Bafang advertises as their "noise grade".
... which is utter BS when they don't list at what distance. Kind of like the rubbish when marketers talk about "share" over various years, whilst omitting how big the pool was.
Also did a muffed road test, and with tire and road noise I got 64db, which is fine.
Be nice if the manufacturers listed things like expected noise levels including the distances their "ranking" is done at, since excess noise is one of the easiest ways to tell if something is busted.