Sound In "Z"
This project was to have sound in a z-scale.
This project was completed few years ago when "SoundTraxx" was the only available decoder.
The problem with using SoundTraxx decoder is the size - it is too big to fit in a standard box car.
Following pictures illustrate the size problem with the SoundTraxx decoder  
In order to fit the decoder in a gondola,  the decoder was placed vertical (Right picture above) and a container built
around it. For power pick up, conductive paint was used with Marklin wheels. Picture below on the left shows the
conductive paint. Picture below on the right is after the conductive paint was painted over with black paint to
conceal it. Only the edge of the trucks was not painted over & is exposed for making the connection.
Pictures below shows the container which was built around the decoder. The small cutout in the center (picture
below right) is for the speaker.
Tantalum capacitors was added to have uninterrupted sound while the train moved over dirty tracks. Picture below
shows the capacitors & the tiny speaker (from cell phone) packaged to fit in the container.
Below are the two movies showing the train in motion with the sound!
Movie
Movie