This is one odd thing that is weirdly exciting! Didn't realize till now we needed it but we do and can't wait for the DLC!
Feedback wise, here is a word soup of thoughts I have about the sounds:
- water ambient doesn't yet feel like it has the right impact, it feels more like a cat fountain dripping rather than a shore or a wavy lake. Not sure about the breathing-like sounds? Need more rustling leaves!
- transitions between driving surfaces seem a little lost in the mix, not nearly audible enough. IRL, driving on brick/cobble would generate quite a loud humming noise, concrete should probably "click" more and be more "echo-y" as the sound wave would bounce off a solid surface and reverb across the factory while grass and earth tiles should mute the sounds more, reduce any reverb significantly and sound more "crunchy", simulating wheels/tracks sinking into the ground and displacing soil and growth. Tank tracks need more of a clack when driven on hard surfaces.
- I love the almost roller-coaster like feeling when a train is passing over elevated rails, but the regular rails now feel a little lacking - need more metallic humming and grinding noises when cornering - which are there but not very audible
- a low rumble and that "psst" sound (anyone who has ever lived near a railway or even been to a train station will know what I mean) preceding a train approaching from a distance when standing near a railway track could be a fantastic addition, both for immersion sake as well as an audible cue for player to warn them of an approaching vehicle
- a transition between elevated and ground rail, it should have a more ramp-like feel. Maybe a metallic clank of loose joints in the structure or dull thuds and pressure-release of built-in shock absorbers (which no doubt a structure capable of elevating a train moving at 300kph within a span of like 10 meters would have to contain)
- crossings/splits need a sound too
- vehicles in general could receive a more complicated sound set seeing as there are never going to be too many cars or tanks active on screen at any one time, nor too many trains moving in one place as they usually space out a fair bit due to throughput. Car feels like it needs a little more low-end noise, maybe an intake whoosh, suspension creaking noises and randomly spaced dull thuds simulating traversing over bumps, brake squealing and .....
gears! One could add simulated gear shifts dependent on speed, purely aesthetic and non functional but would add more immersion and make it feel like you're riding an armored buggy rather than a single speed gokart
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maybe de-couple vehicle engine sound and transitions from being purely speed dependent and instead make them more throttle dependent - louder and deeper with throttle on and more muffled off-throttle. Tank definitely needs a turbine spool like sound to add a sense of weight, menace and power build up which would spool up and stay whistling for as long as throttle is on, releasing rapidly off throttle
- Similarly, trains, which I assume are more hybrid-like in construction (prime mover + generator, seeing as we can power them with a variety of fuels) should have a throttle-dependent sound, building up revs rapidly upon setting off and staying up high when accelerating, dropping to a half-throttle state when cruising at top speed and dropping to idle when decelerating, with addition of dynamic braking hum and light metallic squealing (not too intrusive to avoid driving people insane). Constant engine roar / generator hum + steadily rising electric traction motor hum would go a long way toward making them feel less scale-model like and more weighty, substantial and ...unstoppable
Ultimately mostly nit-picking, and I imagine someone will mod something like this into the game in the future anyway using the new system