"Mandens idé er at blive hørt på konferencen." is also a correct solution :-) The man has the idea that someone should be heard at the conference.

Mandens ide bliver hørt "på" konferencen. Eller "under" konferencen lyder mere dansk!!!

I first understood a second meaning: "The man's idea is to be heard at the conference," or "Mandens idé er at blive hørt til konferencen."

Oh. I am redundant. Just read previous post.