We call the RB211 "kidney stone grinders" because the low noise and vibration you feel going through you, while standing close to a starting RB211. I have always wondered if that's because of the triple spool or the complicated pnuematic system regulating the airflow.
I think it's a great engine btw having seen it stall during a ground run at take-off power and just continuing after that if nothing happened. A CF6 would have been written off.