Kind of a strange horn question.

[hoborich]

When I'm trainwatching at the Wyandotte depot, the approaching southbound NS trains horns can hardly be heard a half mile away. I know they are blowing the horn, because the ditch lights are flashing. The horn gets extremely loud from about 100 yards away, up to the crossing. Despite the horn being barely audible approaching southbound, I can hear it loud and clear several miles to the south, going away, approaching Pennsylvania road, and Sibley road. Just seems kind of strange.
Inquireing minds want to know these things.

[CSX_CO]

Some of the railroads, CSX anyway, have been mouting the horns 'backwards' on the newer GE's anyway. Most of the bells face backwards. I believe this was to alleviate some of the noise the crew is exposed to.

You mention NS though, so I don't know if they'd been doing that or not.

Practice Safe CSX

[azimmer]

Could it be possible that the area just north of the depot is a quiet zone?

Some neighborhoods have ordinances that forbid passing trains to use loud horns. I have noticed very quiet horns being used at the residential crossings between Delray and the NS bridge in Detroit, for example.

A. Zimmer

[SD80MAC]

CSX_CO is correct. EMD and GE have been installing horns with all but one bell facing backwards. Some sort of new FRA ordinence IIRC.

[hoborich]

Well that sounds reasonable, but kind of defeats the purpose. The horns I'm referring to, sound loud as hell going away, and for a couple miles down the track. From Oak street, I can hear a southbound NS blowing for Pennsylvania road, but not for Northline rd, just to the north. I know they are blowing the horn, because the ditch lights are flashing. Mounting four of the five bells facing backward makes no sense at all, for a warning device. I'm going to take a closer look at the horns in the daylight.

[SD80MAC]

Small picture, but shows the set up of the bells.



Yeah, doesn't make much sense.

[hoborich]

Thanks for the pic. Sort of explains it. Like putting the siren on the back of a fire truck.

[azimmer]

The function of a horn, or "bell" as it is called here, is not to impart a direction to the sound. The horn provides an impedance match between the transducer (the thing which vibrates) and the surrounding air mass. The impedance match allows the maximum transfer of energy -- and a train horn produces a LOT of energy.

But the point is that in spite of its deceptive appearance, a train horn will radiate omnidirectionally. Pointing a horn towards the back of a locomotive does not diminish the sound level at the front. This is especially true for the low frequencies that make up the horn signal, which are only about 300-400 Hz.

Currently, however, there is some research being done to develop a directed horn. This is in response to citizen complaints about the excessive noise of a passing train. (People are becoming more and more vocal about the unwanted train in their neighborhoods.) These special horns are only experimantal at this time but maybe they will be standard equipment in the future.

A. Zimmer

[hoborich]

Ummm, well thanks. Still doesn't explain why the horn is heard at a greater distance going away, than approaching.

[azimmer]

Well, if there is a difference in wind velocity at the right altitude, which does sometimes occur, the sound waves will reflect away from the ground layer and the result could be a diminished sound level. But that wouldn't be likely in your case. The same conditions would also effect the area to the south of the Depot.

If I recall correctly, the last time I caught a train at Emmons Blvd., which is a few miles north of the Depot, the horn was not loud. I suspect that the neighborhoods in that area have some of "quiet zone" in effect. (This is just a guess based on an incomplete recollection due to the fact that I wasn't really paying close attention to the horns.)

The only way to tell is to hang around the Emmons Blvd. crossing or some other place to the north and observe the situation there. If the horns are at their normal loudness level, then I would say that the Wyandotte Depot is somehow in the Twilight Zone. If the horns are actually quieter, then there must be some local quiet zone in effect.

A. Zimmer

[CSX_CO]

On most new locomotives the horn is either "On" or "Off". There is no 'feathering' the horn valve like on older locomotives. So, its either "on" or "off". Quiet Zone means there is additional crossing protection in place (4 quad gates for example) and the horn isn't blow AT ALL. There is no 'quiet horn' and 'loud horn' settings.

Practice Safe CSX

[azimmer]

I've noticed that when these locos pass through certain neighborhoods they seem to give only a short, quick blast on the horn which makes it very quiet compared to when they give a prolonged blast that lasts several seconds.

You can't switch the horn into "quiet" mode, but you can make it appear very quiet with a short blast. They sometimes do the same thing to signal that they will begin to start moving after a stop.

This may be occurring at the location north of the depot, where there are a lot of suburban homes very close to several crossings. It would not officially be a "quiet zone" but I can't think of anything else to call it. Trains passing west of Delray on the NS line, where the homes are just 30 feet from the rails, also do the same thing.

A. Zimmer

[CSX_CO]

I've noticed that when these locos pass through certain neighborhoods they seem to give only a short, quick blast on the horn which makes it very quiet compared to when they give a prolonged blast that lasts several seconds.

You can't switch the horn into "quiet" mode, but you can make it appear very quiet with a short blast. They sometimes do the same thing to signal that they will begin to start moving after a stop.

This may be occurring at the location north of the depot, where there are a lot of suburban homes very close to several crossings. It would not officially be a "quiet zone" but I can't think of anything else to call it. Trains passing west of Delray on the NS line, where the homes are just 30 feet from the rails, also do the same thing.

A. Zimmer

Federal Law has guidelines for horn blowing when approaching a railroad crossing at grade. Most of it involves "15 seconds to no more than 20 seconds of warning." Warning being the time the horn is 'blowing'. Anyone who doesn't follow the "Two Longs, a Short, and a Long" appropriately is begging for a lawsuit should they hit someone. All a lawyer has to prove is that warning wasn't provided, therefore it wasn't their clients fault they got hit. I always blow for every crossing, even if another train is 'blocking' it on another track. I'm not going to put my job on the line just because I'm near some 'houses'. Tracks were there first, if they don't like the horns, don't live there.

Secondly, two toots signals "proceed ahead" when using the horn to give signals. I do them, normally when around places where someone might have crawled onto the train, or when I have a crossing blocked. Three 'toots' signals backup, just so you know. I do it for the liability reason again, I can show I 'gave warning' prior to moving. Incidentally, there are a whole bunch of others that really don't get used much anymore in the radio age (apply brakes, release brakes, recall flagman, etc).

Practice Safe CSX

[SD80MAC]

There's also a "long, short" signal for when the train is approaching a platform, tunnel or bridge, but I don't know if that's used anymore. One engineer I know always acknowledges whistle posts with a short toot before doing the long long short long, don't know if that used to be a rule or not.

[azimmer]

I know all about that federal law and that's why I was so surprised to hear these "quiet" signals.

The next time I go to Delray Junction -- which may not be for a while -- I'll have to closely observe what's going on. There are three crossings less than 200 ft. apart. If memory serves, I don't recall ever hearing three separate "two longs, a short, and a long" at 15-20 seconds each for trains that go through there.

Maybe I'm just too busy setting up the camera.

A. Zimmer

[CSX_CO]

There's also a "long, short" signal for when the train is approaching a platform, tunnel or bridge, but I don't know if that's used anymore. One engineer I know always acknowledges whistle posts with a short toot before doing the long long short long, don't know if that used to be a rule or not.

Some guys will start at the whistle post and keep going through the squence until they reach the crossing. Others will 'toot' at the whistle post to show they acknowledged it on the tapes and on CSX and NS units get the ditchlights to start flashing.

IIRC the rule for blowing your horn approaching passenger platform only applies to trains STOPPING at the platform, otherwise you ring your bell through stations. You are supposed to blow before entering to tunnels and thru truss bridges. Not many of those (tunnels) in the upper midwest. I want to say its two longs a short and long for both those instances. Also supposed to blow when meeting a stopped train, blow along the length at various intervals to provide warning for someone on the ground, and blow when approaching the rear of a stopped train. Oh bell is supposed to be ringing when passing a stopped train or standing cars.

Whew!

Practice Safe CSX

[CSX_CO]

The next time I go to Delray Junction -- which may not be for a while -- I'll have to closely observe what's going on. There are three crossings less than 200 ft. apart. If memory serves, I don't recall ever hearing three separate "two longs, a short, and a long" at 15-20 seconds each for trains that go through there.

I blow a 'hurried' "two longs, a short, and a long' for every crossing I come to if close together. If its got crossbucks on up, I blow for it. We have several spots where the crossings are very close together, but I still get the full squence in. It isn't 15-20 seconds for EACH crossing, but the time starts for the first crossing and I keep going until all crossings are occupied.

I'm not going to have some weasel lawyer putting me on a stand and accusing me of not providing 'ample warning'.

Practice Safe CSX

[GreatLakesRailfan]

As far as the original question in this thread- don't forget about the Doppler Effect (check it out on Wiki, or use Google).

Also, I've noticed crossings on several different railroads where the train doesn't blow its horn for the crossing, because the loudspeaker by the crossing signals makes up for it. I've noticed it specifically in Dekalb, IL, on the UP (same UP line that goes through Rochelle) and on the CN, near where the EJ&E crosses near Mundelein (sp?), IL. I've found these loudspeaker arrangements to be quite interesting as it would seem that they kind of defeat whatever purpose whistle bans would serve.

[azimmer]

The Doppler effect only alters the frequency (pitch) of a sound and not the loudness.

If anything at all is happening, it is most likely some kind of refractive effect where,
due to certain atmospheric conditions, the sound bends away from the ground causing
a sound "shadow."

This web page explains it with some animated graphics:

http://www.kettering.edu/~drussell/Demo ... fract.html

This page only discusses a temperature difference but a difference in wind speed
can cause the same thing.

The problem with this explanation is that any atmospheric conditions north
of the depot would also be present south of the depot and the train would appear
quiet from both directions. If the ground surface were drastically different
between north and south, like concrete/asphalt versus vegetation, then maybe
some kind of temperature gradient could be more localized, but I don't think
there is any difference.

A. Zimmer