To give you an idea of how loud the engines are they have a big loudspeaker and they play the sound of one engine running. I remarked to a submariner about how very loud it was.
He said the elfn safety people made them turn the sound down a lot as it would be too loud for the public walking through.
The submariners worked between those two engines with what to me was an unbelievable noise 24 hours a day, except when they run underwater on the electric motor.
Also they did not have ear muffs or any form of ear protection in those days.