I have played for some hours now, and here is my detailed thoughts about the new sounds, starting with the things I feel most strongly about:
New sound tech includes:
Listener position set to centre of screen by default. This will allow you to hear what you see even when in map mode.
This is a cool idea but having tried it, I think I preferred it being set to the player's location.
Previously I would find a nice location in my factory, with comforting sounds of industry, and look at the map from there.
Now it feels weird to look at the map and hear sounds from a radar image. I feel like I'm not tied to my body anymore.
If the listener position goes back to being at the player's location, I also think the map's Zoom Level should not affect the volume. It should be fixed at the value of the player's "not-in-map" zoom level to give the best sense of connectedness to the player's character, and reinforce that the radar image seen on the map is (potentially) far away.
All transport belts, splitters, inserters, assembling machines, power switch.
I play in lategame, so I always use only blue belts. I think the blue transport belt is far too whiny. As others pointed out, it sounds like a dentist drill. Like the roboport, this is a sound the player will hear a LOT, so it needs to sound delicious. :> I had a think about what I personally would do if I was making a sound effect for belts, and to be honest I really have no clue how I would do it. It's really hard to make something good that doesn't get annoying after a while, and adequately conveys the belty nature of the object. All I can suggest is to try a bunch of different options, and we'll fall all over ourselves to tell you if you hit on a good one. :> The transport belt sound effect is super important so I definitely think it's worth spending extra time to make sure it's right.
The inserters sound good with the different tones for different arm directions. However long-handed inserter (and perhaps others) has a "creaky door" effect within it, I dislike that.
Pump, pumpjack, boiler, heat pipe, offshore pump, substation.
I love these new sounds, they are awesome. I didn't hear the heat pipe yet but I heard all the others and they are really cool. :>
Listening to the offshore pump on the map, I noticed that pressing A or D and moving the screen slightly away from it, would make it cut out very abruptly. Then panning the screen back towards it, it would start playing again very abruptly. It's particularly noticeable with pumps/offshore pumps because they make a constant sound, rather than an intermittent one.
The same thing happens (to a lesser degree) when I run past with a lot of exoskeletons. I think it's mainly an issue on the map, as we can scroll around significantly faster than any train or vehicle.
I could propose a solution. Create a "maximum delta" for sound changes, so they aren't allowed to rise or fall in volume by more than some fixed value per update. If it's expressed in percent, an example would be to not allow more than a 5% volume change per game update. Then it would take about 350ms to fade up from 0 to full volume, and vice versa.
Logistic and construction robots, roboport.
I play with roboports everywhere - a full mesh grid with perfect spacing. So everywhere I go, there is now this particular tone playing. It's a nice tone, but I wish it wouldn't be playing continously like that, it gets slightly annoying after a few hours.
Rocket takeoff sequence.
The door opening sound is great. The sound of the rocket itself left me wanting... I feel like it needs some thundering, oversaturated bass. A real rocket launch also sometimes makes a series of short sharp "ripping the air" sounds, once it starts getting higher. Example:
https://youtu.be/OnoNITE-CLc?t=102
That sort of effect might be quite cool to include, it's a nice detail to prevent it being too droney.
One issue I noticed with the rocket launch is that if you are not close to it when it starts, but arrive (or look at it on the map) when it's already halfway airborne, it doesn't seem to make any sound. It could also be that I was looking at the rocket, which is now some ways above the rocket silo, where the actual sound source is located. If that's the case, perhaps the sound source of the rocket should follow the rocket's position instead of staying at the silo.
Train.
These are some cool sounds, but I feel like the levels aren't right. It's very subtle, I had to zoom in a lot to hear it. I'm unable to comment on whether it sounds like a real train or not.
Added some UI sounds that were missing.
I liked all the additions I heard. :> I still wish for sound effects for shift-right-click and shift-left-click. There is no visual or audible confirmation that these operations succeeded at the moment, unless the object visibly changes recipe, which isn't always the case (one example of this is train stops).
The ability to turn off the Doppler effect in Lua, used for the Substation so far.
I didn't notice this yet but Doppler effect is so cool.
environment-audible-distance setting increased to 30 so you can hear entities a bit further away.
zoom-volume-coefficient changed so you can hear more of the world when you zoom out. This will help with combat and give a greater sense of the overall factory.
I didn't notice much effect from these, but they sound like good changes. Will the increased number of sound sources have much of a penalty on performance?