You just need to add keep.xml file manually in the android/src/main/res/raw folder like image below:

And add this code in keep.xml

    <?xml version="1.0" encoding="utf-8"?>
<resources xmlns:tools="http://schemas.android.com/tools"
    tools:keep="@drawable/*,@raw/emergency" />

Change emergency in code to your sound name which is in raw folder