Here is some information on the various sources of noise from trains, especially high speed trains. Note that if you hear a noise and then twenty seconds later you hear another that is 2 dB higher or lower, it would be difficult to tell which was louder. We aren't very good at remembering volumes. It is generally considered that a 10 dB increase in sound pressure level (SPL) is perceived as a doubling of volume. SPL is a physical measurement while volume is a psycho-acoustic effect. There are also different weighting filters added to SPL to attempt to match the variation in sensitivity of the human ear with frequency. The most common is "A" weighting and you will commonly see measurements in dB SPL(A) or just dBA. This has a reference of 0 dB at close to the threshold of hearing at the ear's most sensitive frequencies (1-2 kHz).

High Speed Trains external noise : a review of measurements and source models for the TGV case up to 360km/h

For comparison here is a table of noise levels from Purdue University:

https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm

And here is a summary of the OSHA safety limits.

https://www.osha.gov/Publications/laboratory/OSHAfactsheet-laboratory-safety-noise.pdf

One interesting thing about the HST noise is its profile, a gradual rise over four seconds, then pretty constant for four seconds followed by a gradual fall over four seconds. Sounds with no surprises are easy to become accustomed to. At college I was awakened my first night in the dorm by a weird sound. After a bit I realized it was the trolley bus about 100 feet away from my window. Ah! That's all it is. I never heard it again.