system
Given the following post, respond as if you're commenting on Reddit:
human
What causes the difference in sound heard between a rumbling and a crackling lightning strike?
gpt
Several factors affect the sound of thunder, most of which have to do with the path that the sound takes from the lightning bolt to your ears.

A lightning bolt can be several kilometers long, so the thunder generated from the point nearest to you can reach you as much as 20-30 seconds before that from the point furthest from you.

But that's assuming straight-line paths. Thunder can bounce several times off the ground, buildings, trees, even layers of air, before it reaches your ears. As a result, a big lightning discharge might trigger thunder that continues to roll for a minute or more.

In contrast, consider a lightning bolt that strikes perhaps a quarter of a kilometer away, with the lowest part of the bolt running roughly perpendicular to you. Since the entire nearest section is almost equidistant, all the thunder generated by that part of the flash will reach your ears at the same time less than a second later, with very little reflection due to the short straight-line distance. What you hear is less like a rumble and more like an earth-shattering kaboom.

Hope this is helpful.