Changing pitch of positional sounds

Troubleshooting sound
1

Hi,

in my space game the player can control the speed of his space ship. I want to simulate the engine sound by altering the pitch of the sound - the faster the space ship, the higher the pitch.
Since this is a multiplayer game the engines of other ships should work like this too, and they also have to be positional.
This combination (positional sounds + changing pitches) causes really bad sound artifacts. When I don’t change pitches or I don’t mark my AudioNodes as positional, they don’t occur. Is this a known issue?

I tried disabling reverb, but this did nothing.

Here is the code I use for the AudioNode:

AudioNode audioNode = new AudioNode(assetManager, "assets/sounds/engine1.wav", DataType.Buffer);
audioNode.setLooping(true);
audioNode.setPositional(true);
ship.attachChild(audioNode);
audioNode.play();
ship.addControl(new EngineAudioControl(audioNode));

And here I change the pitch in my EngineAudioControl:

float forwardSpeedPercentage = moveInfo.getForwardSpeedPercentage();

float pitch = 1f + (forwardSpeedPercentage / 4f); // forwardSpeedPercentage has maximum of 1.0

if (currentPitch != pitch) { // I save the current pitch so I don't call setPitch on every frame unnecessarily
	audioNode.setPitch(pitch);
	currentPitch = pitch;
}

And of course I added the 2 lines for the listener in my SimpleApplication.simpleUpdate method.

I even tried this with a really simple sin-wave (created with Audacity), both with the .ogg and .wav format.

I’m testing this under ubuntu 18.04 on a desktop PC, I don’t have any other sound issues and my ubuntu (and therefore my sound driver) is up-to-date.

Any ideas? Do you need any more information?

1 Like
2

Maybe it’s the pitch competing with the Doppler effect that the sound API tries to do for positional audio?

I’m not sure if there is a way to turn that off or not.

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3

I found an old OpenAL guide online:
https://www.openal.org/documentation/OpenAL_Programmers_Guide.pdf

I found the section titled “Doppler Shift” on pages 14-15 to be interesting and relevant.

OpenAL offers a couple ways to tune doppler effects. Unfortunately, jMonkeyEngine’s ALAudioRenderer doesn’t seem to expose any of them.

Seems like a feature worth adding: not all games take place in environments where sound propagates at 340 world units per second.

Btw, for a space game, strict realism would imply no external sounds at all.

PS: A partial workaround would be to scale down the world so that passing ships move at less than 1 world unit per second.

4

Without sound most space games would end up really dull… even Star Citizen, which aims at high fidelity simulation, has sound in space, because silent games suck :wink:

I will probably end up using a different workaround: other ships have positional sound, but don’t change their pitch, and the players ship (that doesn’t move away from the camera a whole lot) is not positional, but changes pitch. Guess I’ll have to live with that.