Duplo Sound Block for Gears & Marble Run

Part of the [Duplo Gears Project](https://www.thingiverse.com/thing:2268803) but can also be used with Hubelino or printed Duplo Marble Run.

Special Duplo block to generate sounds. Can be used both vertically and horizontally. Dimensions and design are optimized to work with official Duplo Gears, printed gears and gear rods, as well as Duplo marble run systems such as Hubelino as sound steps.

The "long" version is probably the best compromise between flexibility and stability for now.

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