I'm a cabin manager on a B777 and have been flying for a number of years - all I can say is I always encourage you to point out anything at all that you see as being unusual - whether you see it, smell it or hear it.
I actually specifically mention in my briefings to my crew that they should always take any comments from pax seriously and report them to me or the Capt. Just the same I always ask the crew to let us know of the same issues as well.
Unfortunately there are some crew out there who don't respond the best when the same "normal" nosie that they hear everyday is pointed out but do know that we very much value your concerns.
As others have said once crew have been seated for take-off they normally won't respond to call bells, if you notice something then you'll need to get a crew members attention another way (pressing the call bell multiple times will normally be enough).
History tells us that had pax & crew spoken up many times that very unfortunate outcomes would have been very different.
So speak up - if it's something normal we'll let you know and if it's not then that's your good deed of the day!
Happy flying.