If you have DCC decoders already installed in your locos, a simple and inexpensive way to add sound is to install an MRC Sounder sound only decoder. The MRC Sounder comes in generic steam or diesel versions and can be found on the internet for around $ 35. I have not had any experience with the steam version but can speak to the diesel one. The sounder decoder is small, measuring about 1/2" square, and comes with an attached capacitor and plug in speaker. The speaker is mounted in a small enclosure and measures about 1" in diameter and 1/2" thick. Hookup is dirt simple, connect two wires to the electrical pickup in the locomotive, that's it. The Sounder is functionally in parallel with the DCC decoder, so any programming commands sent to the DCC decoder are also picked up by the Sounder.
The diesel Sounder is packed with sounds and options, 3 distinct prime mover sounds, 6 different bell sounds, and 22 horns plus a slew of other sounds like air pump, dynamic brake, coupler clank, air release, brake squeal, and more. The volume of each sound is individually controlled by CV's. The downside on the Sounder is a lack of comprehensive documentation and the fact that some CV's in the Sounder are used by other functions in the DCC decoder. For example, when I programmed CV 50 to change horn type, the rear headlight no longer worked. I discovered that the Digitrax DCC decoder I had used CV 50 to control the rear light and if it was set to anything but 0 the rear light would not work. In order to get the horn sound I wanted and keep the rear light working I had to first program CV 50 to 6 to get the horn selected with the DCC decoder and the Sounder both connected in the locomotive, then disconnect the Sounder and reprogram CV 50 in the DCC decoder to 0, then reconnect the Sounder. If I install any more Sounders I intend to add a very small hidden switch that would disconnect the Sounder without having to take the locomotive apart to enable separate programming of the DCC decoder.
Bill
The diesel Sounder is packed with sounds and options, 3 distinct prime mover sounds, 6 different bell sounds, and 22 horns plus a slew of other sounds like air pump, dynamic brake, coupler clank, air release, brake squeal, and more. The volume of each sound is individually controlled by CV's. The downside on the Sounder is a lack of comprehensive documentation and the fact that some CV's in the Sounder are used by other functions in the DCC decoder. For example, when I programmed CV 50 to change horn type, the rear headlight no longer worked. I discovered that the Digitrax DCC decoder I had used CV 50 to control the rear light and if it was set to anything but 0 the rear light would not work. In order to get the horn sound I wanted and keep the rear light working I had to first program CV 50 to 6 to get the horn selected with the DCC decoder and the Sounder both connected in the locomotive, then disconnect the Sounder and reprogram CV 50 in the DCC decoder to 0, then reconnect the Sounder. If I install any more Sounders I intend to add a very small hidden switch that would disconnect the Sounder without having to take the locomotive apart to enable separate programming of the DCC decoder.
Bill