What are “singing rails” and why do they make such unusual sounds (3 photos + 2 videos)

Sometimes it can be quite melodic or eerie.





Sometimes when traveling you can hear this sound:

 

Moreover, the sounds are tonal; if desired, they can be copied and sung. The sound “walks” - the higher the speed of the train, the higher the pitch. Why is this happening?

The reason is due to the grinding of the rails.



Rail grinding train

Special trains remove rust and eliminate rail deformation. And it's not always perfect. The machines are equipped with abrasive discs, which are difficult to calibrate 100%, which causes unevenness on the rails.

Each rail is ground with a separate abrasive disc, so the irregularities on them do not match. On the conditional “first” rail, the unevenness will be at point A, and on the “second” rail - at point B, which is further away. When the train moves, forced vibrations occur: the wheel bounces on every bump and does not have time to land before the next ledge. If the amplitude increases, the wheel skips two bumps in a row and comes into contact with the road surface just before the third bump.



Abrasive discs for rail grinding train RShP-48

The amplitude is affected by:

The degree of “rolling” of grinding.

The wobbling movement of carts as the wheels move from the most rolled-up central track to the peripheral zones.

And the wheelsets create a sound with a tone of ½, ⅓, ¼, etc. “base” frequency, this is determined by the grinding period and the speed of the composition.

For example: the distance between irregularities is 2-2.5 centimeters, the train is moving at a speed of 70 km/h. Then the vibration on the rails will be about 880 Hz, and this is the note “A” of the second octave. The main condition is a harmonious relationship between the distances between the irregularities, then you will get a combination of sounds. And the rails will sing.