Sound-absorbing material on existing hardwood floor.

What would be the best sound-absorbing material to put on existing hardwood floor to reduce noise and echo in museum? 10,500 sq ft to cover.
PS: Cost? Labor?

Carpeting. Carpet runners. Etc…

It would be difficult to determine what steps to take from a forum with little information posted ,however there are many ideas that could be tried and you have more than one issue here as the echo has more to do with walls and how sound absorbent they are.
Bare wood floors may have squeaks that can be eliminated from below,you could add foam underneath for instance or have loose nails,etc but you need on site advise and you can reduce echoes in walls by adding sound absorbent materials there which has nothing to do with the floor.

I thought this question looked familiar!

You are correct, Jeff. I first posted it in Dec. 2011, but could never find the answers. Now, I see them. So, we’ll go with the carpet!
Thank you all!