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Whats That Sound??


Juelz4309

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Ive Always wondered What and Where does that "chew chew chew" Laser Sound That eminates outta nowhere as a train enters the station???...I was boarding Tha Downtown (A) train at 116 street (late nite) and Its a very distinct Sound...its a cool Sound jus wondering Does anyone know why?... Is It the Tracks themselves,warnings,etc??..Thanx;)

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He's referring to the rail "singing" before the train passes. To hear this clearly, watch a video of an Acela, AEM7, or in some cases MNR passing at a high speed on a straight track. Usually one doesn't hear it when the train is slow.

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Thank You Amtrak7 For Your Dignified Response...I knew Someone had to know what I was Talking About!! :cool: ...For those who dont know what Im talking about ....Simply board a Downtown local at 116 st/8 ave.....AND LISTEN lol...

 

I thought you can't hear it from inside the train with the doors closed.

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Ive Always wondered What and Where does that "chew chew chew" Laser Sound That eminates outta nowhere as a train enters the station???...I was boarding Tha Downtown (A) train at 116 street (late nite) and Its a very distinct Sound...its a cool Sound jus wondering Does anyone know why?... Is It the Tracks themselves,warnings,etc??..Thanx;)

i tend to hear it more with NTT's than the older trains in underground stations..i know what your talking about lol

 

and like said before im guessing it must be the tracks too

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pressure waves making the rails vibrate enough to emit the sound of the wheels rolling over joints & the trucks moving around & the flange bumping around against the rail head. Remember, rails are steel, and steel transmits noise/vibration like that readily, all most like a bell. Most solids transmit sound from impacts, and usually faster than through air, so you hear it coming from the rails a bit sooner than from the actual event location. Same goes for overhead lines, especially if they have a very high tension applied.

 

If you want a better visual example of how this works, get a slinky & stretch it, then pluck one part, that wave is what's traveling through the rails

 

- A.

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Though the running rails do emit some sounds due to the train, usually the more distinct "chew chew" sound you hear is the third rail shoes hitting the third rail end approaches at the beginning of a third rail run, which they frequently place at the beginning of a platform. The NTTs sound louder because their third rail shoes are sprung tighter (they push on the third rail harder).

 

I figured this out because when I heard it, I only heard half as many "chews" as there should be if it were the wheels hitting a rail joint (two per truck). There is only one third rail shoe on each side of the truck, so I got suspicious. So the next time at the station, I went to the end of the platform, and there was a third rail gap there. 2+2= (or I should say 1+1=)...

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