The kids bikes are obnoxious.
The big bore bikes (290, 300, 321 etc.) aren't any louder, and they can be run at even lower RPM, though whether this effects true decibels or only a perception there of is a question.
Compared to the other bikes in your sig line, any of the modern rigs will be nearly silent....
ATGATT: When you fall off your motorcycle, you will be wearing what you were when you got on your motorcycle. Dress accordingly.