Propagation of sound after lightning?

Question

In an area of frequent thunderstorms, I notice a 'crack or whoosh' sound if a strike is nearby but little or no thunder. Yet I can hear for 30 seconds or so after a distant flash when the thunder first is heard, the sound starts at a high frequency and then evolves into a deep rumble that can shake the walls. It approaches the sub-sonic. What is the relationship between the distance and the energy of the strike?

Answer 1

There is no relationship between distance and the energy (expended by) a lightning strike; you are not a favored observer in the post-Einstein universe! But, when lightning strikes (and there are usually multiple bolts within the initially opened path, before all the charged areas of a cloud have discharged as they will, but you don't hear the separation between, your ears are overloaded with sound if the bolt is close), the plasma in the bolt path heats air adjacent, violently, starting a pressure wave that 1) spreads in all directions, though not necessarily equally, 2) differentiates in frequencies: the higher frequencies (hisses) spread fastest, but dissipate more rapidly with distance, whereas the lower frequencies (rumbles) dissipate less, bounce better off features on the ground, and travel effectively around obstacles on the ground by diffraction.

The same is incidentally true of all waves: light doesn't travel around macroscopic corners, but does around microscopic ones, and high-frequency sound travels line-of-sight but low-frequency gets out everywhere: you hear trucks a block away even though you can't see them. When you start studying this you rapidly find out that the ratio between the wavelength of the wave and the size, etc. of the confounding object(s), is what determines the propagation (movement over time) of the wave.