Maybe go with a larger fan that runs at a lower RPM? I switched from a 20in box fan to a 27in industrial drum fan and it is more quiet due to the lower fan blade speed. As a bonus it moves much more air and I get a full body breeze.
I use Aftershokz bone conduction headphones which have 0 noise deadening / cancellation and no issues with the big fan. I grew concerned about damaging my ears with daly high volume music while on the trainer and like the bone conduction. I use them at work too and can hear everything around me and people think I have headphones on and cannot.
Dyson fans are very quiet. It depends on how much cooling you need, but I’m fine with one of the smaller ones. It is so quiet that I can run in in hot summers in the bedroom. They’re horribly expensive though, but look cool and the laminar airflow is also quite nice.
I got a set of decibulz moldable ear plugs. Assuming you don’t want to hear anything, thats the way to go. Me? I want to listen to stuff. Being the ingenuitive lad that I am, I cut the ear canal plugs out and stuffed earbud headphones into them (fits like an oversized replacement tip). I think they do make a version with builtin earbuds, but I was worried they’d rust out eventually or something. This way, any cheapo set will do.
I looked into this last summer as a result of this thread, which you might peruse:
I use over the ear headphones. Bit hot but cuts out all noise.
Btw I suffer from tinnitus. It get worse the harder I train. Knowing that it’ll quieten down when I reduce training helps me put up with it.