Audio Low Pass Filter frequency cannot be set at runtime...


I’ve set up an actor that contains a few sound sources. On one of these sources, I have enabled the low pass filter and have set up some blueprints to change the filter frequency via a lerp. unfortunately, this does not work.

I have verified that the lerp is indeed spitting out the correct, desired frequency, but it seems that it is not possible at the moment to change the frequency at runtime.

This is clearly a bug (otherwise, why would there be a node!)

One of our coders checked the node itself, and verified that it is actually being called…

Does anybody have any ideas about a solution - or know a possible workaround?


How have you “enabled the low pass filter” on your source? With a Sound Attenuation Setting?

The Sound Attenuation Settings are cached on the initialization of the sound for performance purposes. If you wish to implement an LPF during Run Time, I would suggest using a Sound Mix.

Any advice on how to implement LPF using Sound Mix?

I do not.

For processing effects like that, I would suggest employing Submix Effects in the new Unreal Audio Engine. You can add a Low Pass Filter to a Submix and Enable/Disable it or affect its settings via Blueprints. This is a much better way to handle something like underwater triggers or near-death affects, etc.

Hi @dan.reynolds , I know this is a 1year-old-topic, but cannot find the answer anywhere else : how do you add a LowPassFilter to a Submix ? I can’t find such a preset in the engine, and can’t add a specific effect to a submix - only create a SubmixEffectPreset. Any advice ?
EDIT : my aim is to add a specific low-pass effect (progressively during runtime) as a door is closed. Any other solution to simulate the thing would be appreciated (just adjusting the volume doesn’t do the trick, and occlusion seems to fail with animated movable doors)

If you click “create SubmixEffectPreset” there will pop up a list of different effects, including filter! It can be set to low- or highpass.

Well I’ve got DynamicsProcessorPreset, ReverbFastPreset, ReverbPreset or SubmixEQPreset, which one should I pick ?

Hmm I have more than that - what engine version are you on?

I’m using 4.24.3 with new audio system enabled. I definitely don’t have all these choices…

My screenshot is from 4.24.3 as well! Hmmmmm what up with ur engine? :smiley:

I really have no idea… I juste verified the whole engine and nothing more. Any advices here ?

Is your Synthesis/DSP plugin enabled?

I’m sorry I can’t check this now. Back at work on the project soon, I’ll let you know.

That’s it, thanks @dan.reynolds , I had to activated the Synthesis/DSP plugin. Thanks all !