The answer is yes, maybe the supporter's voice is just using a tool, but not all matches in every league.
Even if it is not real, but it is quite good to enliven the atmosphere of the match.
Rarely do people watch football matches or other sports matches that are not full of spectators such as the English Premier League or La Liga on live broadcasts that are broadcast paying attention to the same audience voice throughout the match.
Several times I've watched matches from local leagues in my country where the stadium is sometimes very scanty and they do not use any form of tool to fill in cheer sounds in the speakers, it's always very different to be honest..
This is to say that in such a match, the only voice you will hearing is the voice of the match speculator(s), it's makes the whole experience not look like it's a football match we are watching.
So, really, if football organizers are using tools to fill In cheer voices and drums into speakers as a match is going on, it's nice as long as it keep the viewers entertained, thats all that matters.
Yeah, I admit that sound can create a different atmosphere when implemented in stadiums that don't have many people to watch. but it's a little bit weird when we're right there with an empty stadium. When we watch it on television, that sound can increase our passion for watching more until finish. It's different when watch it directly on an empty stadium with an artificial voice.
That is only part of it, not every league is implementing artificial sound. so far it's only Champion League event I heard it regularly on television, maybe when watching live it on the stadium, that such sounds does not exist. It's only implement it to television only.