sound in N steam is possible , the US kato GS4 can have it fitted, but for UK stuff it would need to be in a loco motored tender loco so the tender is vacant for the decoder and the speaker. forget your farish jinty!!. there is a system out vthere that uses speakers around the layout, and transponding from the loco's to fade the relevant loco's sound in and out at the relevant locations. the only plus side is that you can use whopping speakers and get really good base etc. BUT and it's a big one, once you have the layout sectioned and sorted for the transponding with all the necessary electronics and guff, it is actually cheaper to fit a top of the line sound decoder in each loco as the system is limited to 6,8 or 10 loco's, not sure which, but the cost is restrictive. it is good though. and if you want noise in N? if you can get a digitrax decoder in, it can appear to have sound in the right places. for the average 8x4 or shunting layout, a decoder under the layout feeding a couple of speakers would certainly suffice as the sound is never going to be that far from the loco. if you really pushed the boat out, you could have 3 or 4 sound decoders mounted under the layout of differing types suited to your loco's, and when you want to use a loco, just MU the sound decoders address to it and the sound will match the movement. you would just need to remember whether it was steam or diesel and maybe what specific loco sounds it had loaded. so if you have 3 08 shunters and never use more than 2 at a time, you could get 2 sound decoders for the 08, and just MU them to the loco's in use. obviously you may not want a specific fixed decoder for EVERY loco ( though you would if fitting them in the loco's ) but a selection with suitable sounds could suffice that could fit into your roster.