I recall when the EgyptAir plane was taken down by the nutcase copilot, much was made about the constant talk about “Allah” from him on the black box, thus (ostensibly) proving that he acted out of religious conviction.
Fact is, “god-talk” is common in the Middle East. Even an atheist Arab will use terms like “Alhammdulah” (“praise be to God”), “NishkurAllah” (Thank God”), and “Inshallah” (“God willing”) in normal speech, because that is the cultural way of saying “I had good luck”, “I am happy”, and “I know, right?” in common usage.
Making the “trilling sound” (being US-born, I hate that sound) is simply a way of celebrating……anything. WIthout a placard as you say, could be a wedding…could be a Christian baptism. Same sound.