MFL-Car noise in Tunnel

Rode the MFL westbound from 11th to 30th today, and noticed a dramtically quieter ride, and lesser side to side movements. It was much smoother too. Usually betw. 15th st. and 30th st. the noise heard from within the car is very noisy (or really betw. any stations). The train seemed to be moving along at the usual speeds.

The return trip east however was noisy like it usually is.

Was something done to westbound tracks to quiet the ride (new ties or track or something with the 3rd rail), or possibly some type of maintenance to the car sets? Some of the car sets I've noticed really jerk you side to side betw. 15 and 30. Todays westbound ride was noticeably different.

Also-both eastbound and westbound the operators were more like RR in that they accelerated more slowly, and also came to a stop more smoother. I hope this is a new procedure. Some of the operators are so jackrabbit quick out of the gates and brake too quickly too.

I also rode the MFL westbound to 30th Street on Friday, but didn't notice anything noteworthy on the ride. But then again, I was preoccupied in the middle of it with a phone call (sometimes I love having the signal, other times I hate it, as it was one of those other times on Friday). I'll do it again this afternoon and take note of anything different.
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EDIT: I rode the MFL WB to 30th Street today. There was less noise and rocking, but the train didn't seem to be going as fast as it usually does.