The Dormagen stone sculptor Gregor Davertzhofen showed it to me: The experienced stonemason sets holes in the rock, into which he first inserts the spring, which then receives the wedge. With well-aimed blows, the stonemason drives the wedges, which are lined up in rows, deeper and deeper into the rock. As he does so, the sound of the hammer hitting the wedge increases from blow to blow. The experienced stonemason can hear when the stone will crack in two with the next blow.
By the way: In 1990 Siegfried Lenz published "Die Klangprobe". In his book, it is the blows of fate in which the goodness of people is reflected. I will probably use the sound test more profanely: as a method of murder.
