I got one of these for Christmas from my wife. Basically it is a circuit board with an SD card reader that allows you to play .wav files out of amplified speakers connected to the board. The board can be rigged up with switches to trigger the playing of the sound files or it even allows a DCC decoder to be wired into it so your throttle for instance could control the sounds. The device plays back .wav files that are 16 bit, 44.1khz files (CD quality sound). My intentions with the device is to place the left speaker under my dairy farm / mountain peak and the right speaker under the main street in the village. Using Acid Music, I will take a series of ambient sounds (birds, cows, running water, thunderstorm, cars honking, etc.) and place those on the appropriate channel (L or R). I am planning on using a decoder and starting the sounds when I power up the throttle. In conjunction with the sound from my locomotive, this will enhance the overall experience by adding environmental sounds to the operating session. The larger the SD card you feed it, the longer the wav file can be until it needs to start over. I have played with the board for about an hour, and so far I can say I am quite impressed. I would recommend this solution to anyone who wants to add sound to their layout. --Rob.