Ok I don't know how to put the script in this window to show you (a few people here do though maybe they could help) so I'll just describe it. Work through this step by step because you'll fall asleep if you try to read it in one hit...
Open RWTools and click 'Files' then 'Open Trainsimulator 2012 File' and find the engine.bin file which will be called the name of the loco .bin. For example the default black SD40-2 engine bin file is called sd40_2_black.bin.
You will find engine bin files by following the path
Assets - name of Provider - name of Product - Railvehicles - Diesel - name of loco - possbily a sub category - Engine and it'll be there next to the GeoPcDx file (which is the shape file). So to open the engine file of the default black SD40-2 you'd go...
Assets - Kuju - RailSimulatorUS - Railvehicles - Diesel - SD40-2 - Black - Engine - And there it is... sd40_2_black.bin
(I hope this doesn't come across condescendingly. I don't know what level of experience you have in this so I'll just assume you have none and be very simple and thorough)
Open up sd40_2_black.bin and you'll see that it's basically just a script (or whatever it's proper term is) that tells the game where all the various files for the loco are and in some cases how to use them. Scroll down a little and you'll see the second and third parts are telling it where to find the files for couplers. It looks like this...
<Provider d:type="cDeltaString">Kuju</Provider>
<Product d:type="cDeltaString">RailSimulatorUS</Product>
</iBlueprintLibrary-cBlueprintSetID>
</BlueprintSetID>
<BlueprintID d:type="cDeltaString">RailVehicles\Couplings\Buckeye\Type-E\buckeye_type_e_coupling.xml
See where it says Kuju and below it RailsimulatorUS? It's pretty self explanitory... It states who the provider is and what the product is called, then specifically what the file is and where it's found within the product folder. Pretty simple huh?
So to change horn sounds, or change alot of different things, you just have to change these fields to point to what you want to change to. So for the horn, the easiest way I've found is open the engine.bin file of the loco you want to change, open a second example of RWTools and open the engine.bin file of the loco you want to steal your new horn and scroll down to where the horn part is. (Let's say you want to put the horn from the Horseshoe Curve F7 into the default Black SD40-2) It will look like this...
<Provider d:type="cDeltaString">RSC</Provider>
<Product d:type="cDeltaString">HorseshoeCurve</Product>
</iBlueprintLibrary-cBlueprintSetID>
</BlueprintSetID>
<BlueprintID d:type="cDeltaString">Audio\RailVehicles\Diesel\F7\Cab\F7 Horn Sound.xml
By now you've probably figured it out. All you do is change "KUJU" to "RSC for the provider and change "RailSimulatorUS" to "HorseshoeCurve" and copy the "Audio\RailVehicles\Diesel\F7\Cab\F7 Horn Sound.xml" part over the top of "RailVehicles\Couplings\Buckeye\Type-E\buckeye_type_e_coupling.xml" Then click 'Files' and 'Save TrainSimulator 2012 File'. Done.
Most horns and/or sounds are transferable. I've only come across one loco that couldn't handle engine sounds from another engine but horns always work. If you stuff something up, take a look where the original engine.bin file is and you'll see the RWTools automatically makes a backup every time you edit a file so you can just restore one.
I hope this works for you. Actually I hope it just makes sense. I got hammered drunk last night and am so hungover I can barely remember how to think let alone type
