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Seems like the silo acted as a lens for the shockwave.

Related video from Steve Mould where he demonstrates this with a balloon and sound waves:

https://www.youtube.com/watch?v=RLBmWF9Xo10

[Edit: added correct link]

Tom Scott did a video about another acoustic lens: the "sound mirror" overlooking the English Channel that was intended to be an early warning against aircraft coming from the continent.

https://www.youtube.com/watch?v=04F5osXK4vw

[edit: parent comment has been fixed]

You're absolutely right, thanks. The joys of sharing via mobile...

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