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 quite confusing. Our new Sound Selection Guide can help point you in the right direction. Ultimately you should pick a decoder that appeals to your own sound tastes and preferences. This document will help you understand the various sound effects that are unique to each steam Tsunami Digital Sound Decoder.


Understanding the exhaust chuff

Each steam Tsunami decoder features a different exhaust chuff that was actually recorded from a prototype locomotive 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 sound room 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 Tsunami 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. This becomes important to understand that the dimensions and design of these parts on a 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 smaller 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 2 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 2 exhaust chuffs each time the cylinder moves forward and back. Most locomotives have 2 cylinders that produce 4 exhaust chuffs per 1 wheel revolution (wheel rotating 360 degrees). Some locomotives have 3 cylinders (such as shays and 3-cylinder rod engines) and thus produce 6 exhaust chuffs per full wheel revolution. To help achieve the proper chuff rate, our decoders come with both an adjustable automatic chuff rate and the option of adding a cam that produces an exhaust chuff completely synchronized with the locomotive drivers (main wheels on the locomotive). To make installing a cam simple, we offer our cam kit (SoundTraxx P.N. 810038). Some rod locomotives have multiple sets of cylinders (such as a Big Boy). These articulated locomotives often sound similar to a locomotive with only 2 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 steam Tsunami decoders, by using our “slip rate” feature. You can put select an articulated exhaust with a slow, medium, or fast slip rate.


Understanding the air compressor

Steam Tsunami decoders are equipped with the appropriate air compressor based on the prototype recorded. The sound of the air compressor comes on when the locomotive is placed on a live DCC track. On a prototype steam locomotive this sound is heard any time that the locomotive main reservoir falls below a pre-determined P.S.I. and will continue on until the governor shuts off steam to the compressor due to the main reservoir filling up. The 2 most common types were built by Westinghouse and are known as single phase and cross compound. Both designs are pictured below.
Single Phase Cross Compound

Simply look at your model and determine which type of air compressor(s) your locomotive has to help you select which Tsunami is appropriate for your model. Some locomotives will have 2 air compressors of the same type. Tsunami decoders allows for two compressors so you can make your sound decoder more prototypically accurate.

Older locomotives that were built before the addition of air brakes don’t have an air compressor on them. If you don’t see either of the compressor styles shown above, your model may be based on a prototype prior to the late 19th century air brake era. Since Tsunami decoders have individual volume controls for all sound features, this allows you to set the volume of the compressor to 0 if your model doesn’t have a compressor.


Understanding the whistle

Undoubtedly the most loved and most beautiful sound feature of any steam locomotive is the whistle. Railroads sometimes chose to use just one whistle type for all the engines on their railroad, while others just used whatever whistle was on the locomotive when it was delivered from the factory. The purpose of the whistle was to warn people and to communicate to the trainmen. Below are a few examples of common whistle signals.

- is designated as long whistle blast

o is designated as short whistle blast


- - o - Approaching a public road
- o Warning for areas where view is obstructed
- Approaching a station or flag stop
- - Release brakes
o Set brakes
- ooo Flagman protect the rear of a train
ooo Stopping (When in motion)
ooo Going in reverse (When initially moving)
- - Going forward
oo Acknowledgement of signal not otherwise specified


One of the great features of SoundTraxx sound decoders and DCC is the ability you have to use prototypical whistle signals just like the real thing. Tsunami digital sound decoders have functions for both a long whistle and a short whistle making crisp and accurate whistle signals possible. Tsunami decoders also come with the ability to set up automatic whistle signals such as:

forward (- -), reverse (ooo), a public grade crossing (- - o -), and brakes applied (o).

Tsunami steam decoders come with up to 8 different whistles allowing you to either pick the correct whistle for a specific railroad or to pick one that you feel sounds the best. Remember, many whistles were used on multiple roads, or were extremely similar, so don’t get too caught up in the listed prototype. Listed below are the specific sounds associated with each steam Tsunami. Please note: TSU-1000 style decoders and TSU-750 style decoders contain the same sound files.


Light Steam Tsunami:

Air compressor type: Single phase
Whistles available: C&S #74 (Road mix)
C&S #74 (Yard Mix)
Baldwin Consolidation
Heisler
Westside Lumber Co. Shay #14
Peanut Whistle
D&RGW Single Chime
Reading 6-Chime

Exhaust chuff: The exhaust chuff found on the light steam is recorded from a smaller locomotive similar to those found on short lines and narrow gauge lines. This works well for small engines such as branch line engines or yard switchers.


Medium Steam Tsunami:

Air compressor type: Cross compound
Whistles available: Santa Fe Freight
B&O 3-Chime
PRR Banshee
Lehigh Valley
Nathan 5-Chime (Road Mix)
Nathan 5-Chime (Yard Mix)
USRA 6-Chime

Exhaust Chuff: The exhaust chuff on the medium steam is recorded from a locomotive that would usually be used in either mainline passenger operations or short line freight operations.


Heavy Steam Tsunami:

Air compressor type: Cross Compound
Whistles available: Frisco #1522
Norfolk & Western #1218
Union Pacific #4018
Southern Pacific #4449 (Whistle)
Southern Pacific #4449 (Horn)
USRA 6-Chime
Southern Pacific 6-Chime

Exhaust Chuff: The exhaust chuff on the heavy steam is recorded from a large mainline locomotive. This would be appropriate for larger passenger and freight locomotives on mainline railroads. This includes the large articulated engines such as the Big Boy and the Challenger.


Denver & Rio Grande Western K-Class Tsunami:

Air compressor type: Cross Compound
Whistles available: K-27 #463
K-36 #487
K-36 #488
K-36 #489
K-36 #489 (with broken chime)
K-37 #497

Exhaust Chuff: The exhaust on the K-Class decoder is recorded from the large narrow gauge Mikados found on the D&RGW. This sound is also appropriate for small to medium size standard gauge locomotives as well as other narrow gauge locomotives of similar size.


Southern Pacific Cab Forward Tsunami:

Air compressor type: Cross Compound* (The exhaust port on this compressor is sound-specific to an SP Cab Forward with a truly unique sound as compared to most other locomotives.)

Whistles available: Southern Pacific 6-Chime
Southern Pacific #4449 (whistle)
Southern Pacific #4449 (horn)
Frisco #1522
Norfolk & Western #1218
USRA 6-chime

Exhaust Chuff: This decoder is designed specifically for the different types of SP cab forwards made such as the AC-6 and AC-12


Denver and Rio Grande Western C-Class Tsunami:

Air compressor type: Single phase
Whistles available: C-19 #340 (yard mix)
C-19 #340 (road mix)
D&RGW Single Chime
Westside Lumber Company Shay #14
Peanut Whistle

Exhaust Chuff: The exhaust chuff on this Tsunami comes from a consolidation used on the D&RGW. This decoder is suitable for all of the Rio Grande C-Class locomotives as well as locomotives on narrow gauge and small short line railroads.


Light Logging Tsunami:

Air compressor type: Cross compound* (This compressor is recorded from a Shay locomotive and has a unique exhaust sound found on many geared locomotives)

Whistles available: Westside Lumber Co. Shay #14
Westside Lumber Co. Shay #12
Heisler
Peanut Whistle
D&RGW Single Chime

Exhaust Chuff: The exhaust chuff of this Tsunami is recorded from a geared locomotive. It is appropriate for many different types of geared logging locomotives such as shays, heislers, climaxes, and other small locomotives. These generally ran on short logging lines with extremely steep grades.


Conclusion
By now you should have an idea of which Tsunami is appropriate for different types of locomotives. Let your ears be your guide and select the one that you feel captures your model the best. This is your model and your layout after all, so ultimately you should pick the sounds that are most pleasing to your ear.