Here is an old (long out-of-service) H-series Toronto subway train. On acceleration, it has a distinctive warm, cricket-like sound (@0:35).
Here is a newer (soon likely to be obsolete) T1-series train. It has a deeper, almost spooky sound when it accelerates (@1:14 and @1:34).
Why don’t the newer trains accelerate with the warm chirp of the older model? What causes the much different deeper sound?
Variable frequency drives vs brake squeak?
According to this YouTube video comments I found, it’s a set of thyristors at 400Hz driving the traction motors:
Here is a newer (soon likely to be obsolete) T1-series train.
In Doug Ford’s Ontario, they will be around longer than they should.
They have to save money somehow to pay for the Eglinton line…
Nah, he’d rather give $225M to The Beer Store instead of the TTC.
[Moderating]
A stern reminder that this is FQ. Politicking is inappropriate.
Sorry about that, I intended it as an inside joke for other locals rather than politics after providing a potential factual answer. I will refrain from further politicking!
Copenhagen’s 4th Generation S-Train stock has a distinctive two-tone acceleration sound. It starts as a high-pitched whine, but then after reaching a certain speed it switches to a lower louder pitch.
They run at an odd 1,650 volts DC so perhaps there’s power relays providing some rudimentary gearing to reduce load/stress on the motors when accelerating while also using a more standard motor? The Chicago ‘L’ on the other hand seemed to just go without making much noise at all. That operates on a more typical 600 volts DC.