Here they have two different lines of fans, a super cheap one and a "performance" line that's like $10 more. The pro ones are quieter and seem to last longer.

I was thinking about it this morning, and I sleep with my ear about 6 inches from mine (has to be tucked under the mosquito net) and it is noisier at that distance, but if you're at least 5 ft from it, you should be fine.