I am not going by the claims of the manufacturers, but my general experience with each of these, so it doesn't really matter what the specs are.
When I watch projectors in my large room the projector sits about four feet behind my captain's chair. In the testing room, I'm moving around a lot but am typically 2-4 feet from the projectors and can hear all but the most silent.
Other types of audible projector noise
One last thought before the listings: Not all noise is fan based. DLP projectors have the noise of their spinning color wheels, but at least I'm happy to report that the higher pitched whine of the wheels in older projectors are essentially absent with today's projectors. There is one other factor, which relates to projectors with dynamic irises (most of the projectors in this review). Only in a few cases is the iris action audible. Be warned however, that when it is... The older Optoma designs (includes the HD806 and HD8000-LV) have dynamic irises so noisy, that I don't consider those projectors to be usable with the dynamic iris engaged, we're talking a LOUD clicking sound. Epson has a much lessor problem. Some report their iris to be loud enough to be noticeable/annoying. I've factored that iris into the Epson rankings. One thing that may help with the Epson - if you are shelf mounting, put some sound absorbing material between the feet and the shelf, as I find that the shelf (or tabletop?) may amplify that sound by resonating with it. I don't personally find the Epson iris to be noticeable enough to be an issue, but if you are particularly audible noise critical, it may be.