I just watch the highlight mini match of champions league last night. I watch it all 9 match, and a bit confused when hear all sound from supporter on stadium because all look the same.
you will hear a sound drum strings with the same tone, and sound cheers where almost the same when the player dribbling the ball almost in front of the goal.
I thing that champions league company just use that fake supporter sound to make their show to be lively, This can also affect the audience's interest to watch on each match because the company banded with their ads.
I just know that because there are some stadiums that do not have enough supporters, but the cheers sound already full lively with drum strings also.
what do you think?, is real or use recording through speakers
There are various steps that will be taken by the Champions League company in order to attract people to be interested in watching the football match that will be held, whether in camouflage or real, but in my personal opinion, if the steps he takes do not violate existing regulations, I don't think this will happen. will be a problem.
Yes, as you have said above and the conclusion is that the sound of the crowd cheering, the truth of which is not yet clear, is just a small problem and I think the audience watching the event via social media will not be a problem that will become a problem during the match. It is clear that there is fraud that favors only one club.

Being on the stadium, you might hear different sounds but it all aggregates to a different large noise to viewers. It's mostly cheering that's heard when their are goals. I don't think they add any fake sound effects as that would sound unnatural.
About the viewers on ground, the demand for tickets of champions League matches high and if both the team participating don't have a huge fan following, they'll just lower the ticket more people would come to the game. They may even provide free passes to be a part of it. During our school, we used to get free ticket to support a random team. UEFA might employ those tricks.