Like with TSW 2020 you can adjust the sounds further to be a bit louder. Remember to backup the original file. Documents>MyGames>TrainSimWorld2>Saved>Config>WindowsNoEditor - GameUserSettings This one tended to be popular: MasterSoundVolume=3.500000 SFXSoundVolume=3.500000 AmbienceSoundVolume=2.500000 DialogueSoundVolume=1.500000 ExternalAlertVolume=1.500000 MenuSFXVolume=1.000000 Having tried this myself I think it does help with overall sound when I feel some of it is too quiet, especially with the Bakerloo line. However you might find this to be too loud for CSX and Penn. Adjust it to your suitability
They really need to try and get the balance right themselves, I don't know, if anything to me the sounds seem worse in TSW2! I've played both Bakerloo and Koln route and the track joint sound is just too quiet and it's just not a case of turning the volume up because everything else becomes too loud - also the looping sounds need looking at.
After doing the adjustments, I have plenty of sound in Sand Patch. If anything it is a tad too loud so will probably tweak the settings down a bit.
After following instructions provided in OP, it's interesting how much is going on sound-wise just on the Bakerloo line... the clacking sounds of wheels passing rail junctions are there, but are for some reason very quiet in the mix. Careful listening even confirms the shaking of windows after gaining speed, and the noise in the tunnels is much more prominent. This is a decent patch for the time being, but the sounds in general really need to be re-balanced and added for a more diverse and distinct sound presentation.
The track joint sound on the Bakerloo line is almost non-existent, which is really unrealistic. There is, however, quite a lot of wheel flange sounds