Selecting the Right Sound for Your Steam Locomotive

If you aren’t sure which sounds are appropriate for a given steam locomotive, choosing the correct decoder can seem confusing. Ultimately you should pick a decoder that appeals to your own sound tastes and preferences. This page will help you understand the various sound effects that are unique to each steam Tsunami2 Digital Sound Decoder.


Understanding the Exhaust Chuff

Our steam Tsunami2 decoders feature a variety different exhaust chuffs that were actually recorded from prototype locomotives in action. We record with multiple microphones and create different operating scenarios to capture the “characteristics” of a steam locomotive. We then take these sound recordings to our audio lab where we digitize and loop the exhaust chuffs for use in our decoders (no synthesized sounds are added to our exhaust chuffs). To further enhance the exhaust effects, our Tsunami2 decoders have a feature known as Dynamic Digital Exhaust (DDE), which causes the exhaust chuff to increase and decrease in volume and fullness based on the load it is pulling -- just like the prototype. In addition, a full 7-band equalizer will allow you to further customize the exhaust to sound exactly like the specific locomotive you are recreating.

Exhaust chuffs result from the movement of steam through the cylinders into the steam chest, the exhaust nozzle, and finally through the stack and into the atmosphere. It is important to understand that the dimensions and design of these parts on the prototype locomotive play a much larger role in how the exhaust sounds than the wheel arrangement or road name of a particular locomotive. For example, a small standard gauge engine built by Baldwin (such as a Mogul 2-6-0 with 34,000 pounds of tractive effort) will sound very similar to a larger narrow gauge Mikado 2-8-2 that produces nearly the same amount of power, assuming they are on similar grades and pulling similar tonnage. If you have two models (such as a 2-8-0 and a 2-8-2) that both have the same set of cylinders with a similar diameter boiler and smoke box, they should have very similar sounding exhaust chuffs.

How many exhaust chuffs should your locomotive produce to be realistic? Locomotives produce two exhaust chuffs each time the cylinder moves forward and back. Most locomotives have two cylinders that produce four exhaust chuffs per one wheel revolution (wheel rotating 360 degrees). Some locomotives have three cylinders (such as Shays and 3-cylinder rod engines) and thus produce six exhaust chuffs per full wheel revolution. To help achieve the proper chuff rate, once you've selected the type of engine (for example, a 3-cylinder engine), the Dynamic Digital Exhaust will create the best possible results for your model.

Some rod locomotives have multiple sets of cylinders (such as a Big Boy). These articulated locomotives often sound similar to a locomotive with only two cylinders because both sets are often synchronized. When one set of drivers slips, you will hear an extra set of exhaust chuffs. You can simulate this on our Tsunami2 steam decoders by using our “wheel-slip rate” feature. You can select an articulated exhaust with a slow, medium, or fast slip rate.