Feature request: Speed of sound simulation (doppler effect and sonic boom)

[DancZer]

I would like to request a feature for the Sound engine, which would simulate the doppler effect and the sonic boom as a two major phenomenon.

If you don't know what is it:

Sonic boom implementation in other games:

 

Doppler effect in other games:

 

If an object is big enough, the double sonic boom what is mentioned in the TED video is clearly audible. And what is big and goes fast?! Rockets!!!

I hope you like it and the devs sees a nice addition in such a feature. 

[DancZer]

I made a video where I added sonic boom under KSP2 footage. I tried to do the doppler effect too, but it was hard (probably because of the already high pitch engine (it is much lower in real world)).

Turbine itself is high pitch (when no throttle applied),

but the flame is a flame, so the sound should be similar to rocket flame.

or this, but unfortunately non of these amateuer fotages records the deep sounds, only the high frequencies:

 

[Mushylog]

That would be a great addition to Kerbal Space Program 2. I can imagine this feature to be added later in the game, since it isn't very life-changing. It is very cool so I hope to have this added in the game as soon as possible!

But of course there are other priorities right now!

[Mushylog]

Additionally, it would look amazing if the trails of vapor left by wings in KSP2 would wiggle a bit near the 2/3 of the trail, starting for the end of the trail. Like in that last video you posted.

Edited October 25, 2023 by Mushylog

[Wardein]

I 100% support both ideas and think it should be added

[Snark]

On 9/2/2023 at 1:51 PM, DancZer said:

simulate the doppler effect and the sonic boom

I'm having trouble picturing what you have in mind. The game only lets you fly one craft at a time, so the only sounds you hear are from your own craft, generally speaking.

And you're "riding along" with the craft, as it were:  that is, your frame of reference is a viewpoint that is moving along with the vehicle.

And, crucially:  Doppler effect and sonic booms are phenomena that you can only experience in a different frame of reference from the source.

For example:  Suppose you're a stationary observer, standing next to a race track, and a car goes whizzing past you. Then you get a Doppler effect as it goes past, nyooooooom. Very exciting, yes.

But to the driver of the car, there's no Doppler; they just hear the engine at a constant pitch as they zoom along.

Similarly, if you're standing on the ground and a supersonic jet goes whizzing past, then you hear a sonic boom as it goes past you. But to anyone aboard the plane (or a hypothetical observer flying along right next to it, if they're in the cone), there's no boom, there's just the continuous sound of the plane.

Since KSP pretty much forces the observer to be traveling along with the currently piloted craft, therefore, there's rarely an opportunity to hear any sounds from any other moving objects besides your own craft.

Doppler effect and sonic boom only happen when the observer is moving relative to the source. In KSP, you're always moving with the sound source, so the relative motion is essentially zero, so Doppler effect isn't a thing. Sonic boom isn't a thing.

How did you envision such a feature working?

 

[Stoup]

Rocket sound enhancement mod for KSP1 has sonic booms based on camera position, which kinda works. It gets a bit awkward if you spin your camera around the craft and are bombarded with constant booms, however

Edited October 26, 2023 by Stoup

[Snark]

3 minutes ago, Stoup said:

Rocket sound enhancement mod for KSP1 has sonic booms based on camera position, which kinda works. It gets a bit awkward if you spin your camera around the craft and are bombarded with constant booms, however

I've never used the mod, so I don't know exactly what it does. I'm having trouble picturing an implementation that could simultaneously be "cool" (i.e. engaging for the player) and realistic. Those two things feel mutually exclusive to me. How does it behave, exactly?

[Stoup]

The way it works, it kinda uses the camera position as the external observer you mention. So if you're close to the speed of sound (or I've also heard it when well over the speed of sound during reentry, I'm unsure exactly how that works) and you rotate the camera from being in front of your velocity vector to behind it, you hear a boom as you rotate past that plane of transition. Also, when you're in excess of the speed of sound there's a notable muting of sound effects. I don't think it's always super realistic in this regard, but it shows your point, that it's hard to find a way to represent the phenomenon that isn't just a little janky 

Edited October 26, 2023 by Stoup

[Periple]

I think the MS Flight Simulator vid showed how it could work.

I also think it's not really relevant for KSP ... at least until multiplayer is in, at which point it can become very relevant!

[Snark]

2 hours ago, Periple said:

I think the MS Flight Simulator vid showed how it could work.

The issue is that the videos posted in the OP aren't really germane to the feature request, for the most part.  In order, the videos are:

1. explanation of what a sonic boom is
2. MS Flight Simulator implementation - this is relevant, with some caveats, see comments below
3. MS Flight Simulator - irrelevant, because it involves a stationary 3rd party perspective that doesn't exist in KSP
4. Warthunder - irrelevant, same reason as #3 above
5. Grand Theft Auto - irrelevant, same reason as #3 above
6. Another game video, irrelevant for same reason as above
7. Falcon Heavy landing, also irrelevant for same reason as above
8. ditto

Of all of those, the only one that's actually relevant (because it involves a viewpoint that's flying along with the craft, like KSP), is this video, #2 in the above list.

However, that video doesn't have the OP's requested features in it:

• No Doppler shift (correct, because realistically there shouldn't be one)
• No sonic boom (correct, because realistically there shouldn't be one)

The only thing that that video shows is that they've correctly modeled the "cone of sound".  When the viewpoint is in front of the shockwave cone, then there's no sound from the plane and it's silent.  When the viewpoint moves into the cone, then you're hearing the sound of the plane's engines.  (Without any Doppler, which is correct.)

That is realistic, and it would certainly be possible to model that in KSP if the devs wanted to.  However, I think it's arguable whether it belongs there.  KSP has a lot of realistic physics details in it, but it's clearly designed as "game first, simulator second", and it's by no means obvious that most players would want such an implementation in the game.  If you're flying a jet plane, hearing the engine sound is not only immersive, but also can give you some useful feedback about what's going on (e.g. you can hear changes in engine pitch as you throttle)-- is it really doing the player a service to make them unable to hear the engine depending on camera angle?

Tastes vary, of course, but just speaking for myself, I would find the implementation of "silence outside the shock cone" to be intrusive and unhelpful; it would just irritate me, and I wouldn't want it in my own gameplay.

And there would be no Doppler experience at all, of course.

2 hours ago, Periple said:

I also think it's not really relevant for KSP ... at least until multiplayer is in, at which point it can become very relevant!

Total agreement there.  Sonic booms and Doppler shifts become very relevant when there are moving objects that fly past you.  There currently aren't any such, in the game, because there can be only one moving object (your own craft), and your viewpoint is always following along with it.  As soon as there are other objects, e.g. other players' craft in multiplayer, then this is a very different scenario and these features would totally make sense.

On 9/3/2023 at 3:56 PM, DancZer said:

I made a video where I added sonic boom under KSP2 footage. I tried to do the doppler effect too, but it was hard (probably because of the already high pitch engine (it is much lower in real world)).

Very nicely done, thanks! 

Your suggested implementation looks like it's pretty much what MSFS would do.  It's certainly cool, and it's reasonably realistic (at least for the cone-of-sound, though there shouldn't be any Doppler).

That said, the question becomes:  what would be the attitude of the player base towards something like this?  That is, among the players, what fraction of them would fall into each of the following camps?

1. That's awesome, cool, and realistic.  I want it.
2. It's an annoying and unhelpful distraction, I prefer not to have it.
3. I don't care much one way or the other.  It's way down my priority list of things I would want implemented in the game.

Some players, such as yourself, are in camp #1.  Others, such as myself, are in camp #2.  At a wild guess, I'd suppose most players would be in camp #3.

#2 is a good reason not to implement the feature.  #3 is also a good reason (because implementation takes time and engineering resources, and the devs have plenty of more important fires to put out).  So the only scenario I could see where it would make sense for them to implement the feature would be if a majority of players are in group #1, and it's not obvious to me that that's the case.

(As @Periple points out, though, there's much more reason to have such a feature once multiplayer is added to the game.)

[Stoup]

Honestly, I'd consider it an uncommon enough occurrence even in multiplayer, I wouldn't miss having it much. I guess that puts me in camp 3!

[Mushylog]

@SnarkThe game already simulates different levels of sound depending on where the camera is, relative to the active vessel (and any other vessels around, ie boosters and other parts that generate audio that you can detach from the main vessel). So I think it would be a good idea to have sonic booms, still, even if the game currently does not encourage different camera-view-points. It doesn't encourage it but it's still happening.

Example:  launch a rocket on the pad and activate the engine. Gradually, zoom out and zoom in, you will hear different sounds from the engine.

I say, if we're going to have some fun realistic sound effects, we should go and do it well!

We would be able to launch a "missile" rocket to have it pass by some kerbal located on the ground, and by passing by him we would be able to switch vessels to have his point of view and see the missile pass by + its sonic boom  + its shock cone. It would be a really cool addition in 1.0 !