Where in Europe did the first screening of a sound film take place?

In Europe, in 1919, three German inventors, Josef Engl (1893–1942), Hans Vogt (1890–1979), and Joseph Massolle (1889–1957), patented the Tri-Ergon sound system. On September 17, 1922, the Tri-Ergon group gave a public screening of sound-on-film productions—including a dramatic talkie, Der Brandstifter (The Arsonist) —before an invited audience at the Alhambra Kino in Berlin. By the end of the decade, Tri-Ergon would be the dominant European sound system.

In 1923, two Danish engineers, Axel Petersen and Arnold Poulsen patented a system that recorded sound on a separate filmstrip running parallel with the image reel. Gaumont licensed the technology and briefly put it to commercial use under the name Cinéphone.