There is a discrepancy is how the output volume of a submix is calculated when the effect chain is and is not populated.

When there is no effect on the submix, the Dry Level adds additional gain to the output. Setting the Dry Level to zero doesn't make the output silent. 

When there is an effect on the submix, the Dry level scales the overall output. In this case, setting the Dry Level to zero makes the output silent.

This has some odd effects when dynamically adding a removing effects from a submix and was discovered when trying to use a submix effect chain override on a submix with no effects. When the effects are added, the submix suddenly gets quiet. When they are removed, the submix becomes much louder. This is particularly noticeable when the Dry Level value is less than 1.0

Three videos are attached. simpletest_submixvolume_removefx.mp4 illustrates the discrepancy how the dry level is applied to a submix with and without an effect. In particular, how the overall output gets louder when the submix is removed. The other two videos show using an override to add and remove an effect dynamically with a couple of different settings for wet and dry levels and show how the volume "pops" as the submix effect is added and removed dynamically.



Steps to Reproduce

1) Open the AudioQA project
2) In the Content Browser, Navigate to Content\Levels\Manual \AQ_SoundSubmixAssets
3) Open the Sound Wave VO_QASubmixTest
4) Set its Submix to QATestSubmix
5) In the Content Browser, Navigate to Content\Levels\Manual \AQ_SoundSubmixAssets
6) Open QATestSubmix. Set the Output Volume to 1.0 (0.0 in db) and the Wet Level to 0.0 (-60 in db)
5) In the Content Browser, navitage to Content\Levels\Manual
6) Open the AQ_SoundSubmix level
7) Play in editor
8) Move the camera to the Submix Playback Test toggle
9) While audio is playing, adjust the Dry Level of the Sound Submix
10) Observe that the volume gets softer and louder
11) Select the + next to Submix Effect Chain
12) Add any effect
13) Set the Dry level to 1.0 (0.0 in db)
14) Remove the effect

Expected Result:

 The volume of the sound doesn't change.

Actual Result:

 The volume is louder when there is no submix effect


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ComponentUE - Audio - Submixes
Affects Versions4.275.05.1
Target Fix5.5
CreatedJan 21, 2021
UpdatedMar 22, 2024