Very interesting quote. Once reading about atomic bombs said that the strongest bomb, the bomb of the Tsar in addition to listening to thousands of kilometers, swept the clouds with an expansive sling that went around the globe three times. Now that I say, Finland must be very close to the site of the explosion, perhaps broke the windows of the house of your grandfather friend Markku. Jaja
Too far to break my grandparent's windows. :)
But the sound may have been heard in northern Finland.