Once again, you have come up with an interesting demonstration Frank!
You have introduced a more contemporary Lectron System block as well with the 555 timer block, a mainstay in digital circuit design so long ago. Love it!
I would imagine that the 47uF cap has something to do with the timing of the trigger to generate the sound but I am not an engineer as you are!
Thanks so much for keeping things going here!
Best,
Michael