Audio Design, River: Whither AmbientSoundSpline?

Hey there!

I’m a student audio designer for a project that has decided to migrate from UDK to Engine 4 and I’m just getting into it. For the most part, there seems to be easy transferring from one to other in my department, and the new attenuation shapes are quite welcome. However, there is a long river in the level for which, in UDK, I used AmbientSoundSpline with my river SoundCue to rather easily and smoothly place the sound along the length of the river. AmbientSoundSpline no longer appears to be a base actor class in 4, which makes sad trombones play in my head. I might start looking at the source for the spline class in UDK and see how to recreate it in 4, but that would take a while, and this is just one project out of many that I’m working on right now, and it is due soon, so time is an issue, and I’m worried about having to correct phasing or curvature problems if it doesn’t work out the same. So, I’m just looking for feedback and suggestions for possible strategies in this case. The simplest one would be to create box- or cone-shaped repeats of the sound following the shape of the river best I can, but, again, possible phasing problems, which is probably the reason AmbientSoundSpline was created for UE3 in the first place: using listener position to calculate which node on the spline should play at any given point to get rid of phasing problems on long or weird shaped sound sources.

One thought I had was to, similar to how I’ve done it in a WWISE project attached to a custom engine, have a single point source sound move along the shore line based on the player’s position, i.e., if the river is predominantly running left-to-right on the X axis, give the sound the same X value as the player’s and a specific Y/Z along the center line of the river, allowing attenuation and low pass settings to do their thing. Thoughts on which direction I should go for implementing that? Or, indeed, a better solution (again,one that doesn’t cause phasing by overlapping sound sources playing the same content)?

Also, I’m also missing the old “Fade to Omnidirectional” functionality that let you, once close enough to a sound, let you slowly switch off directional attenuation and let the sound come equally from all speakers, because I can’t find that in the new engine either, and that was a nice switch. Anywhere to be found? Thanks!

Hey there Pgoodso,

I’m glad you made the jump over to UE4. Although the AmbientSoundSpline and Omnidirection sound properties are not “currently” present, there are a few new audio tools that should help get the job done. One of them is the attenuation node. This node allows you use separate attenuation settings for each soundwave. So for your river sound, you can have a mono soundwave handle the directional audio, and the stereo soundwave handle the unspatialize audio. The Crossfade by Distance node will also get it done. :slight_smile:

If you to decide to use multiple actors, try slightly changing their pitches from one another to avoid phasing.


Thanks for the response! One last question: does Crossfade by Distance interact correctly with all attenuation shapes? If so, does crossfade by distance on the box attenuation shape crossfade from the long axis of the box’s volume? Or does it only work spherically (i.e., even with a box shaped attenuation, Crossfade by Distance only works from the center point of the sound’s location)?

Crossfade by Distance is based on the center point of the sound regardless of the attenuation shape. I’m assuming by “interact correctly” you are thinking that you would want the crossfade to start at the inner shape at which full volume is determined? It’s an interesting idea that I hadn’t considered before, I’ll jot down a task to evaluate a way of doing that, however, because attenuation can be applied multiple times, in different shapes, to a single sound identifying where that full sound inner radius is would not be well defined.

Hi guys

Sorry to drag this thread up again, but are there any plans to add the AmbientSoundSpline into ue4 any time soon? I’ve got a limited amount of time working on a game full of rivers, coastlines and rattling pipes so I can see using multiple cues for each of these being time consuming and problematic.

Also, could any of you go into a bit more detail about how to use the attenuation nodes to achieve the same results? I’m also using FMOD so if there’s any way of getting it done using FMOD events then I’m all ears!


I’m quite disappointed that over two years later there’s still no ambient sound spline support in UE4. It’s really frustrating and I hope that the feature is still up for consideration. This was a really powerful tool in UE3 and it’s sorely missed.

Since I was just looking for an answer to this, I’ll leave my finding of a possible solution here for everyone else who might end here as well:

Hi Guys,

Many years later, I am also looking into this. Any news regarding ambient sound spline support in UE4? Might it return in UE5? Using Wwise here, I noticed the link above my post, I wonder if there are other or more updated solutions around by now?

Thanks in advance!