The sound travels at about 1 mile per 5 secs. In addition to the above, there may also be echoes from proximate hills/buildings. Also, the cell will have multiple lightning events crackling away one after the other, so you'll be receiving a chorus of claps. Thunder is heard up to about a max of 15 miles away. So you might hear the near one plus echoes, followed by one 5 miles away plus echoes (not as loud), followed by another 10 miles away etc.
Given that it was a cold front, then a squall line is probable, so you might have heard from more than one cell concurrently.
The total result reaching your ears depends on how God rolls the dice.
