Rail3D*

 

Steam

Steam locomotive Sound Scheme

The Steam sound scheme is designed for steam locomotives. The primary sound from a steam locomotive is the “Chuff” of the steam leaving the chimney, a chuff being produced for each beat of the cylinders. Thus the number of chuffs per wheel revolution will depend on the number of cylinders, and the rate will depend on the speed the wheels are going round, which of course, is directly proportional to the locomotive speed (except when slipping!)

At low speed, the chuffs are discrete and should coincide with puffs of smoke from the chimney, at higher speeds the chuffs merges into the characteristic steam locomotive sound. 


    
        Steam
        Steam\Steam
        10
        0.32
    
    Steam\Whistle

The Rail3D Steam is more complex than other Rail3D sound schemes and operates in different modes at different engine speeds. Two sound channels are used, although one always plays the background engine hiss.

  • At all engine speeds, one sound channel plays the default engine hiss: Steam0
  • At low speeds, the sound system plays single “chuffs”, synchronised with the exhaust coming out of the engine’s chimney: the sound set needs to include a single chuff wave: SteamC. This is possible as long as the time between exhaust beats exceeds the length of the single beat file (SteamC), hence the <beat> parameter in the above code which specifies the length (in seconds) of the single chuff file. Once the beats are coming faster than this rate, the system switches to the next mode:
  • At speeds were discrete chuff sounds are not possible, the system selects the sound file according to the wheel rotation rate (and therefore speed) with the second wave Steam1 for the lowest speed, moving up the last wave file for the highest speeds. Note that unlike the rpm sound scheme it is not practical to fade between sounds, so there will be some discontinuities when changing between wave files.
  • If the engine goes in to a slip, the wheels will spin rapidly, and the highest wave file will be played.
  • At all speeds, the volume of the sound is related to the regulator position.

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