The Xion DD motor on my Kalkhoff PC is pretty much noiseless and the little Tongxin motor on my Cannondale is more or less silent too.
Equally, I have ridden Dutch bikes with the Ion-Drive system, (DD) and couldn't discern any significant noise from those either. My early Panasonic motor in a Dutch bike was also silent.
However, most other EAPCs I have ridden, particularly those with geared motors have been very noisy. One of the worst was the GoBike, which I thought sounded like a milk float but it was a surprisingly capable bike.
I did wonder at one point if it was just my diminished hearing causing me to not hear what others perhaps hear so I actually wore my hearing aids one day to compare. Mistake! While hearing aids can actually help a little with failing hearing, what they do really, really well is to amplify every extraneous sound and wind noise had me ripping them out after a few hundred yards!
The message has to be: If you communicate by sign language, buy any bike you want!
Tom