It's also dependent on the room/building you are in. If you would try the fan in an office type environment (even without any people there) you would probably t

It's also dependent on the room/building you are in. If you would try the fan in an office type environment (even without any people there) you would probably think it is quiet. But then when you bring it home the fan suddenly sounds very loud. It's mostly due to the background noise such as active ventilation, air conditioning, other computers/servers/printers with fans etc in the office, which you might not have in your house. The empty office might seem very quiet, but in terms background fan like noise it's not. Traffic noise could also be a similar background noise factor.