Originally Posted by Minnewaska
I don't have them myself, but suspect the ones that I've heard were getting old. Its wasn't horrific, but you could hear it. It would depend on your tolerance for it. I think experiences have been mixed.
One's brain quickly filters out irrelevant background noise. As a child we lived in a big old house with a late 1800's era Grandfather clock in the library, off the foyer, that tick-tock'd away mightily. Supposedly one could hear it throughout the house, unless one lived there. When called to one's attention by a visitor, one would have to "listen" for it before it could be "heard". So the whoosh of the fans in our solar vents, although they are nearly inaudible to most everyone unless one is standing directly below or beside them. To us, after a day or two aboard, it is their absence, if they become inoperable, that one notices, not there presence. Just as one notices an unusual tone or vibration in the engine in one's car, or aboard ship a change in the tone of the wind in the rigging when on passage.
Actually, now that I think about it, the "moan" in the cowls in a gale on our prior yacht was quite inconvenient and, at times, could be quite alarming until one realized the source.