The first two halls make no sound at all — the machines are started only in the third.
The idea is simple: show the mechanics first, and only then let the result be heard. In the first halls the machines stand dismantled or with their lids open, with explanations of what connects to what.
In the third hall two machines are started, and according to the attendants almost every visitor then walks back — to look again at what they have already seen.
