Sense, Nonsense, and Not-Sense

Carpeting might also help. I'm reminded of that every day in our place, which had most of the carpeting ripped out and laminate put in its place (ignore me if the library's already mostly or fully carpeted). Carpet muffles noise quite well and is fairly quick, easy and cheap to install until something can be done about ceilings (another problem our place has and you're right, high ceilings combined with an open floor plan (ditto here) will increase noise exponentially).

Also (edit, based on a quick glance above right after posting) as at least one other poster's said I too am offering this in the same vein as others have of sharing ideas you can gather and share at say, the next meeting where Things That Can Be Done might be reasonably brought up for discussion, and I do empathize all the way, both as an avid reader who would want your library as peaceful and usable as you might desire it to be and as someone who wants to support you in your role as a librarian. I used to spend a lot of time in libraries, myself, and appreciate what they have to offer.

I just hope this isn't going to devolve into people attacking those of us on the thread offering up ideas, as it seems to have, already.