My friend has the Kato UP executive train with the sound decoders in the E-units and also couple (or three) TCS sound effect decoders sprinkled among the passenger cars. Those produce some random squeals and rail-related noises. They are adjusted the volume low, and the effect is amazingly good. The 3-dimensional sound (not just the locos) really works, especially when the train passes in front of me. When he told me he was installing them in the train I was skeptical, but now I love it!