How do the horns on engines work? I know that depending on the engine, one either pushes a button or pulls a handle to make the horn go. But why do different horns sound different and how do the makers of the engines decide what the horn will sound like? And once the button is pushed, what process occurs to get the horn to go on and off?
Compressed air is routed and blown through the horn to put it bluntly. The horns aren’t made by EMD and GE and so on. They are made by people like Airchime, Nathan, Leslie and a few others. The railroad specifies what model horn and type will go on an engine. The old horn levers were air valves. Which means when the valve was opened, compressed air passed through the lines and out of the horn. If I’m not mistaken, the new buttons are valves but aren’t manual, they are electronic valves. Randy Stahl can help out on this topic I’m sure. Hope this helps!
Willy, just noticed you had 567 posts, one of the best sounding EMD engine models ever!!!
Nothing to add UPTRAIN you got it!!!
Randy
Minor note (not in the sound of the horns except in Canada, ha, ha!)
Unless I’m missing something, the compressed air going to most of these horns doesn’t come out the bell. It vibrates the back side of diaphragms in the ‘power units’ at the back of the trumpets, and the air at the front of the diaphragm then moves, in resonance with the volume inside the trumpet, to project the sound waves.
Actuation is via a valve which admits air from the brake reservoir to the ‘motor’ side of the diaphragms. Exhaust is automatic. Conventional locomotives have a manual valve, but other locomotives have an electric (solenoid) valve; the latter can be easily controlled via software to give the famous “autohorn” (if programmed by certain geeks in Erie, the results can be as laughable as indicated in other posts of recent memory here!)
The notes and chord played are selected by the type and dimension of horn bell used (just as with organ pipes, for similar acoustic reasons). To an extent, the different individual horns will ‘speak’ at different pressures or delivered volumes of compressed air, which is why you will often hear a horn blow only a few of its notes if the valve in the cab is only slightly opened by the engineer or whoever.
Horns can go out of tune, and some designs are much better than others in holding tune and requiring less, or easier, maintenance. There are a couple of very good and useful Web sites that describe and show horn construction, and feature .wav files of how they sound.
Sometimes it sounds like the engineer is slowly pulling down the lever. One tone will sound, and then it gets louder and another 2 or 3 different tones join in.
Wily2,
If haven’t seen them, you’ll like these websites. Go to these sites:
http://atsf.railfan.net/airhorns
You’ll need Media Player or similar feature on your computer to play the sample horn sounds. I learned so much about horns, uses, and histories on sites like these. Whenever I go railfanning now, I try to identify the horns that I hear.
Hope this helps, enjoy![:D][8D][dinner][C):-)]
Thanks everybody! I’ll check out those websites later today.
I don’t know much about horns, but I’m pretty sure very little compressed air is going to come out of these “bells.”
I’d never noticed this before a few weeks ago. Are the actual horn bells just for show now?
Radivil… no, the bells aren’t for show, there’s screening across the mouths to keep bugs, ice, etc. from getting inside. High-speed railroads have cones in front of the mouths, for a different reason: high-speed air makes the horn note ‘burble’ and can even keep the bell from sounding… if you look at the Turbotrain in late NH-line service, and I believe at some of the Metroliners, you’ll see this installed. (I believe some of the Los Angeles cab cars converted from Metroliners still have their cones).
I don’t want to toot my horn ! but I am a musician with most of a four year degree before I dropped out.
I was checking out the web site, very cool.
I have always thought that the five chimed horns were tuned in a non repeating series of tones like 1, 3, 5, 7, 9. (1through 8 = an octave), and the three toned horns were augmented (#5), or suspended4 (#3).
But on the web site, it says the horns were all tuned to major chords - 1,3,5,7,1 or 1,3,5. Except they are all tuned with “inverted” voicing - 3,5,7,1,3 or 3,5,1. It says that because of lack of maintenance, the tunings of individual horns would drift, giving the odd chords.
What I thought was augmented or suspended, was actually diminished because the 3rd is in the bass, I’m saying that only to cover my *** if someone who knows music asks “how can it be augmented, because the horns are going flat with time?” - instead of the 5th going sharp, the 1st (a distance of six between 3 and 1) went flat, and it says on the site that the horns go flat with time.
Anyhow, its interesting to note that the inverted tuning of a dominent 7 chord (3,5,7,1,3), puts the 7 right in the middle. As far as frequency in hz goes, the seven in this position splits the diference between the low 3 and the high 3 exactly, and the five and the one which are usually the strongest tones in a chord, “take a step back” to the sound of the odd diminished fifth (b5).[:-^]
Wow, a real musician!
I’ve been looking forward to seeing a musician’s analysis of horn design and tuning for many years now… since before the Amtrak horn-design period.
Another thing to consider is the Canadian insistence on their ‘government’ chord tuning; discussing why this was picked would be particularly interesting.
One thing I’ve considered in horn tuning is the effect of Doppler-shift pitch changes on the frequencies and beat notes resulting when the horn is moving at ‘typical’ speed. This is a bit more complex than might be expected, and I invite comments on what to look for, the ‘ideal’ tunings for approaching and receding speeds, etc.
Mooky started a thread a while ago comparing the sounds of EMD’s vs. GE’s, I think it was called “Me Again” but could be wrong. Anyway I had some comments of why an exhaust stroke of a Two stroke sounds different than a four stroke - more bass in 2-stroke, and how the expansion of sound waves affects the diffrent frequencies of sound comming from the locomotive differently, so that the next time you hear a train from far away, you could pick out the parts of the sound and hear the affect.
Although doppler effect spreads out the distance between frequencies, the relationship between the frequencies remains the same. A difference between 1hz and 2 hz is %100, But the difference of one hz between 99 hz and 100hz is only %1, so while the percentage of difference between two notes changes, the musical relationship does not - a “5th” is still a fifth, whether three octaves below middle C or three octaves above middle C. One thing that does change when raising or lowering a fundamental is that the composition of harmonics that as a whole creates the “timbre” of the sound will change, but that has to do with the physics affecting the source of the sound.
I have always listened to mechanical things with a musician’s ear, and it’s no accident when the torque curve, and the horsepower curve, the resonant frequency of a cylinder, the resonant frequency of tortional vibration in a crankshaft, resonant frequencies in the drivetrain all line up perfectly at the ouptput and speed of a vehicle that is “cruising”. In the case of a locomotive the prime mover’s vibrations are in harmony at a speed and output that is in harmony with the alternators optimum speed and the traction motors are balanced physically and electrically at a speed in harmony with output of the alternator and all of these harmonies ocurre at a speed and output in balance with tractive effort that is at the cruisiing speed of the locomotive. THIS is how the engineers get payed the big bucks.
At Conrail, we started testing these things in the late 80s. They are mesh fabric with an elastic band to hold them on over the horn bell. We called them “snow bonnets”. The biggest problem we had was snow backing the bells and renedering the horn ineffective. The design of the Leslie horn actually does exhaust some air out the mouth of the bell in order to help keep it clear, but not enough to overcome the snow packing problem. The snow bonnets worked well enough in tests and were proven not to attenuate the sound any measurable amount that they became part of the annual winterization procedure.
While the whole rest of the world calls them solenoid valves, the RRs, for some reason buried back in history, calls them “magnet valves” - which still bugs me even after 26 years of hearing it!
THESE are the sorts of details that make forum use delightful! Carry on!
I’d forgotten about ‘magnet valves’. Be interesting to find out what GE calls 'em inside Erie… and how many of their engineers share our irritation at the use of the older term.
Have any of the Western railroads adopted the use of these bonnets, and if so, where?
Here’s another question.
A lot of times on SD70 MAC locomotives, the engineers don’t seem to blow the horn for long, they just do short little toots. Is there a reason for this, or do I just happen to end up with all of the trains that do short blows.
I was wondering that too, Willy. On older locomotives, the engineers seem to blast the horn for a long time (thus doing the requiered hooooooooonk hoooooooonk honk hooooooooonk) while the newer locos seem to go hoonk hoonk honk hoonk.
I have always wondered if the sound of train horns are what inspired musicians to experiment with dense complicated chords, and the clickity-clack of the wheels inspired synchopated rythm giving birth to jazz. Maybe even as far back as steam boat whistles, compared to barbershop quartet harmonies.
I can picture a young musician riding a train for hours, listening to these sounds. I know that I tend to trance on repetitive sound, and over time it morphes in my mind into ideas for songs.
There is a guitarist named Adrian Belew, who has a very cool train song called “Swingline” that is on his album titled “Lone Rhinoserus”. It mimics the sounds of trains in a kind of psychadelic art deco style. It’s kind of be-bop 50’s style with breaks of backward masking, steam hissing, and stumbling rythm. The lyrics paint rockwell pictures of american backyards as seen from a train. Very cool, I urge anybody to check it out.
While you’re at it, don’t forget that classic of early '70’s jazz, “K4 Pacific” by Gerry Mulligan. A very definite improvement on Pacific 2-3-1 by Honegger (which Honegger, famously, denied had anything to do with sounding like a train…)
Listen for the sound of the brakes going on.
And don’t forget Tom Rush’s cover of Panama Limited… one of the most expressive endings ever recorded.