High pitched noise coming from tracks

[straller]

Hello,

I've noticed this phenomenon quite often on UK railways, so I'm sure there's a name for it but I don't know what that is. Instead of trying to describe it, I'll provide a video.

This was taken a few years back on the Stansted Express train, just north of Harlow Town on the down line. The noise is only audible above 65 mph or so. Sometimes it changes pitch quite rapidly, although I didn't capture that on this video. I don't hear this noise at all on the trains in my home country, so I've come to associate it with my UK visits, and I'm wondering what is the name of this sound phenomenon.

 

[Bald Rick]

That’s rail that has had a recent visit from a rail grinder.

 

[AM9]

That’s rail that has had a recent visit from a rail grinder.

I'm not so sure. To me it sounds more like typical Electrostar variable frequency drive resonating in the motors. It seems that the sudden changes of pitch would be related to the changes of loads on the traction system. Railhead serrations tend to make more of a roar as with the sound of multiple wheels in contact, there is no coherency to create a single frequency. (Sorry, it's a bit early to get the right words to describe that).

 

[fgwrich]

I'm not so sure. To me it sounds more like typical Electrostar variable frequency drive resonating in the motors. It seems that the sudden changes of pitch would be related to the changes of loads on the traction system. Railhead serrations tend to make more of a roar as with the sound of multiple wheels in contact, there is no coherency to create a single frequency. (Sorry, it's a bit early to get the right words to describe that).

I have to agree with Bald Rick on this one - I know the sound you mean, but this is definitely that sort of lower pitched noise you tend to get from freshly ground rails. It’s a sound you quite often hear on the Desiro’s along the SWML (Eastleigh to Basingstoke seems to be ground fairly often), and sometimes on the IETs along the GWML.

Also, that video appears to be from a STADLER.

 

[nlogax]

This is something I've often heard on higher speed services, more commonly on ECML services in 91s + Mk4s.

 

[Ash Bridge]

Another one here with @Bald Rick I reside close to the Heaton Norris - Guide Bridge line and when the rail grinder has been down overnight every type of train creates this exact whining sound for a good few weeks afterwards, regardless whether it be a Sprinter through to the Drax Biomass and heavy aggregate services. Just thinking about the OPs video clip where the sound pitch appears to change quite rapidly, perhaps this is perceived as the train passes by closer structures such as platforms or similar?

 

[XAM2175]

Also, that video appears to be from a STADLER.

Pedantry: "Stadler" is a name like Alstom or Siemens, but "FLIRT" is capitalised because it's an acronym.

 

[themiller]

Having listened to the video, I don’t understand how the changes in pitch would be generated if due to grinding - I’d have expected a pitch varying with speed which doesn’t seem to happen, here. I would have thought along the same lines as AM9 would be a more logical answer because the sound changes smoothly rather than abruptly.

 

[richa2002]

This is 100% sound related to the track and rail grinding. Not traction motors. The sound often, but not exclusively, changes rapidly when going into or out of a curve.

 

[AM9]

I have to agree with Bald Rick on this one - I know the sound you mean, but this is definitely that sort of lower pitched noise you tend to get from freshly ground rails. It’s a sound you quite often hear on the Desiro’s along the SWML (Eastleigh to Basingstoke seems to be ground fairly often), and sometimes on the IETs along the GWML.

Also, that video appears to be from a STADLER.

According to the OP, the video was taken a few years back, presumably well before the Stadlers were delivered. Any modern EMU with IGBT three phase inverters can make that sound, and eually on DC as much as ac track. In my experience, the sound is more noticeable on Electrostars - maybe because they seem to be of lighter construction and the sound travels through the body structure more readily. Even the 700s seem to have this electronic hunting which I think is the traction control optimising the frequency for coasting, cruising and accelerating.
Interestingly, the sound is present when braking, but doesn't modulate in the same way, usually just decreasing in pitch until almost at a standstill, which would be consistent with a constannt braking setting being applied.

 

[physics34]

Definately recently grinded.

 

[43096]

According to the OP, the video was taken a few years back, presumably well before the Stadlers were delivered.

The seats and interior look like a FLIRT.

 

[straller]

Thanks all for your replies. I did some research earlier and I thought it could be because of the grinder, but nowhere did I find an example of the actual sound.

I'm not so sure. To me it sounds more like typical Electrostar variable frequency drive resonating in the motors. It seems that the sudden changes of pitch would be related to the changes of loads on the traction system. Railhead serrations tend to make more of a roar as with the sound of multiple wheels in contact, there is no coherency to create a single frequency. (Sorry, it's a bit early to get the right words to describe that).

According to the OP, the video was taken a few years back, presumably well before the Stadlers were delivered. Any modern EMU with IGBT three phase inverters can make that sound, and eually on DC as much as ac track. In my experience, the sound is more noticeable on Electrostars - maybe because they seem to be of lighter construction and the sound travels through the body structure more readily. Even the 700s seem to have this electronic hunting which I think is the traction control optimising the frequency for coasting, cruising and accelerating.
Interestingly, the sound is present when braking, but doesn't modulate in the same way, usually just decreasing in pitch until almost at a standstill, which would be consistent with a constannt braking setting being applied.

The video was actually taken just one year ago, in 2021, I was mistaken when I wrote the title. The video is indeed from a Class 745 FLIRT. But I have heard the same sound in Electrostars, IC225s, IETs, etc.

 

[Shaw S Hunter]

It's not unique to the UK, I have experienced similar in Germany. Again it was much more noticeable at higher speeds. But the speed doesn't have to be that high. The worst case of it that I have ever experienced was long ago on LU's Victoria line on the long inter-station stretch between Seven Sisters and Finsbury Park. Of course within the confines of a tube tunnel the noise had nowhere to dissipate and it made conversation in the train impossible. LU put up posters explaining that passengers should not be alarmed, that it was caused by recent rail grinding and that it would eventually settle down. As it indeed did but it took a few weeks.

Although I am no track engineer I believe the cause is an interruption to the normal process of wear between the rail head and train wheels. Wheel treads are routinely re-profiled to a particular pattern, almost but not quite flat across the tread width and at a particular angle to the plane of the axle. Thousands of wheel passes over the railheads creates a consistent wear pattern between the two but rail grinding interferes with this process. The sound is effectively due to the "corrective" interaction between the two surfaces in the period following grinding. I would suggest that when rail grinding takes place one aim is to avoid creating this mismatch but clearly this isn't always possible. Happy to have an expert add more detail.

 

[DarloRich]

I wonder what the noise is like if the miller has beem along that section of line

 

[WizCastro197]

Thanks all for your replies. I did some research earlier and I thought it could be because of the grinder, but nowhere did I find an example of the actual sound.





The video was actually taken just one year ago, in 2021, I was mistaken when I wrote the title. The video is indeed from a Class 745 FLIRT. But I have heard the same sound in Electrostars, IC225s, IETs, etc.

Hmm. At First I wasn't able to tell what sound you were referring to in the video as I hear it so often as you mentioned on the Electrostars.


Forgive me: What exactly does a grinder or a grind of the tracks do? I have looked it up but you all are far more interesting than Google.

 

[Bald Rick]

Forgive me: What exactly does a grinder or a grind of the tracks do?

Grinding: in simple terms it grinds off a small amount of the rail head to remove any minor defects (including microscopic cracks that can develop into bigger cracks) and restores the correct profile (shape) of the running edge to provide the best contact with wheels.

Also the heat generated by the grinding process causes the metal to change structure, slightly, to help reduce defects further.


Milling: literally shaves off the metal, rather than grinding it.

 

[themiller]

I wonder what the noise is like if the miller has beem along that section of line.

I understand how it could be produced by traction electronics but what I was after was someone to explain the mechanism of the generation of the noise if it comes as a result of rail grinding. I could probably come up with a theory but it may or may not be right. It’d be good to hear from someone who’s sufficiently informed to give a definitive explanation rather than just ‘It’s X’.

 

[DerekC]

Very sadly Prof Roger Goodall of Loughborough Uni, who was (amongst other things) a world expert on vibration at the wheel-rail interface, has recently died so we can't ask him. It's really complicated so I am not surprised we have competing explanations! I recall him explaining one of his projects which could measure the adhesion at the wheel-rail interface by very accurately measuring the lateral vibration of the wheelset and correlating it to the track curvature etc. I don't know what happened to that one - I suspect that it proved too difficult to translate from the lab to the real world.

 

[hacman]

This isn't inherently just due to grinding, but more due to the rail/wheel interface. Grinding will, however, increase it.

You'll hear this on the ECML on the 80x fleet, 91+MkIV and I think the Voyagers do it too. I've also heard it on 390s on the WMCL, and on higher speed rail in other countries.

Having listened to the video, I don’t understand how the changes in pitch would be generated if due to grinding - I’d have expected a pitch varying with speed which doesn’t seem to happen, here. I would have thought along the same lines as AM9 would be a more logical answer because the sound changes smoothly rather than abruptly.

Grinding isn't a 100% uniform process - the amount of grinding done in any given location varies based on the condition of the rails and ground rails can produce a variable hum when travelled over. It's also worth remembering that the point at which the wheels contact the rails isn't perfectly linear - the wheels will move and hunt depending on a number of factors.

 

[Irascible]

It's not unique to the UK, I have experienced similar in Germany. Again it was much more noticeable at higher speeds. But the speed doesn't have to be that high. The worst case of it that I have ever experienced was long ago on LU's Victoria line on the long inter-station stretch between Seven Sisters and Finsbury Park. Of course within the confines of a tube tunnel the noise had nowhere to dissipate and it made conversation in the train impossible. LU put up posters explaining that passengers should not be alarmed, that it was caused by recent rail grinding and that it would eventually settle down. As it indeed did but it took a few weeks.

Yes, that bit of the Vic has sounded like a demonic choir at times ( although I'm not sure if that was grinding or just the old stock being absolutely thrashed down there too! ) ... wierdly not experienced anything like that much Finsbury to KingsX.

Heared that sort of noise in pretty much anything on the main lines. HST runs oin the GWML used to make all sorts of tunes.