People are free to enter.
Last time I was there the nature reserve was fenced off. Access is very limited and only allowed when accompanied by a park ranger. Except last year when all the ponds were iced over and somebody gave a blanket permission to all ice skaters to enter.
I think even the aerobatic competition box is within hearing distance.
The aerobatics hold is normally placed at the western tip of the ATZ/SRZ and is two lateral miles from the fence, approximately. The aerobatics box is slightly further away from the fence at approx. 4 miles. That's most likely hearing distance, but I wonder if it's close enough to actually cause a disturbance.
Furthermore, there is a highway and a railway line in between.