We had a deck 7 Promenade room on Navigator, we were in 7305 IIRC, so not quite midships, but we heard no noise, even when the Parade or 'Dancing in the Streets' night was on, we could only hear a little muted music. Not enough to disturb you if you are early to bed. The only people who hear noise are those directly over the pub, from the comments I have seen online.. it's a great place to people watch..
Remember that you are overlooked and you overlook the opposite cabins, so don't forget curtains....!
The parade starts late on the first night, around 10-30 or 11pm, goes on for an hour or more, and the Dancing in the Streets starts around 9ish IIRC and lasts a couple of hours.
The best place to watch the parade is right outside the pub, you can see both ways and a lot of the action takes place on the 'bridge' over the Promenade at that point.