[Desti314]

I'm curious if this is really the answer and not something like sound tunneling and amplification.

Like when you stand somewhere further away and there is a spot were you can very clearly hear the people talking across the street or on a balcony

[joshspankit]

Natural amplification (especially through materials, which is what I would guess happened here) is resonance. It’s wild how pervasive it is.

[JetSetIlly]

An excellent demonstration of this is The Whispering Arch in Liverpool Anglican Cathedral or The Whispering Gallery of St Paul's in London.