Subject: Is there a formula for time after hearing an explosion?

Based on how far away you are and when you hear an explosion is there a formula
to calculate when it will hit you?:
In "Under the Dome" by Stephen King a (huge) C-4 and propane explosive went off
and a few people had time to seek shelter. Also, I read historical accounts of
survivors of the Hiroshima bomb from different distances. Each had some time
before the fragments and heat hit near them. 

Re: Is there a formula for time after hearing an explosion?