... we are told not to make many noises including slapping the mat. I guess the reason is that they don't want to disturb the neighborhood .. but doesn't that make the practice incorrect?
Long time ago I used to practice in a dojo where from a certain moment on it was forbidden to make noise because of the neighbours. And because of that there was no slapping any more.
I noticed that after some time the techniques changed, so the students could fall them without making some noise.
I don't know about correct or incorrect but waza changed, became different.