I know you would prefer a tower, but if you do consider a pedestal fan, then I can recommend the Lenwoy Smart Cooling Silent Floor fan. I took delivery of it from Amazon on Tuesday and it is as near silent as I think it is possible to get. It has a load of settings - I think up to 15 - and has a remote control. I has 7 blades, which make it more efficient, and it has an 8 hour timer.
I haven't had it on above level 6, and I only really started to hear slight noise at level 5.
It was quite expensive, at £80, but having used it I don't feel quite as ripped off as when I ordered it