What is a normal hearing distance?

Question

Given low ambient noise, what is an average hearing distance? How far away would a person with normal hearing be able to clearly hear and understand a conversation held with normal voices between two people? At what distance would the conversation become hard or impossible to understand/hear?

Evidently I should clarify. I know that there's a lot of variables, but I'm interested in a rough estimate. Please assume that there is little to no wind, that ambient noise is low enough not to matter much, and that the sound is a conversation at normal room-level voices.

Perhaps this isn't a question with an answer. That would be a shame.

Answer 1

pardon me,say it again please

Answer 2

so many variables - inside , outside
wind + or -

have heard voices a 1/4 mile across a lake on a still night

have been in the US capitol and 'listened' to the star as the guide walked across the room and spoke at the other star - and we heard him whisper from 100 ft away (it bounced off the dome)