What is the range or distance in which sound may be heard?

I've laid in bed and counted out a lot of lightning. I had this question myself and googled upon it as I wondered if there may be discussion involving it. I've read the humidity, temperature, wind and other factors would be involved so I would imagine it would be a comprehensive calculus equation to determine the time exactly at any given moment during a occurrence. So...not having found a divinitive answer to my question, and I'd like to head to bed and count some lightning/thunder in the storm approaching, I want to conclude to myself what I've discovered in my investigation, this evening...

I don't remember ever hearing thunder over 25 or seconds later. 5 or so miles away. I've lived in Iowa all my life (51 now), so I've enjoyed (been vigilant for my families safety) a lot of lightning and storm (possible tornado activity) watching. So, I would imagine it would be around 4 to 6 miles, normally the shock-wave would be absorbed by the atmosphere. More or less depending on the various conditions.

I've been in thunder snow. That was strange.

I've also been in a storm that dropped hail the size of baseballs! I never want to see that again! Insurance claims repaired maybe half or more of the roofs in town. It only lasted a minute, but the damage was incredible and the noise as it approached created a fear in me I've never had before and never desire to experience again. I appreciate staying within a safe distance of a strong shelter when a storm is around.