Hi,

I have a old forced-air, hot-water heating unit in the cellar, hanging on
the ceiling.
It's a Trane "model S" Unit Heater, about 2'x2'x1' in size, electric fan in
the back of it.

The fan is really noisy, but motor seems in good shape otherwise.

What can I replace it with?

Are newer residential heaters of this type any quieter?

(This is a loud commercial unit, I guess, because the Trane website states
these "units provide uniform heating for large open areas in such
applications as warehouses, factories and showrooms.")