One of the jarring experiences of watching the Bundesliga is seeing the action happen in front of empty stands. The referee's decisions escape the fury of a crowd. You can hear the players communicating with each other and make out what they are saying. And when the ball hits a post, there's this eerie, booming noise.

The sounds are similar to a training game. You hear every kick, scuffle and the precise moment the ball hits the net. They are noises synonymous with football and ones we hear playing with our mates in the park, but not at the highest level where this is usually drowned out by the passionate fan support.

So when the Bundesliga returned, one of Germany's broadcasters, Sky Deutschland, devised a plan to convey the familiarity of atmosphere to all of us forced to watch from home. Some media markets would get the choice of a "no crowd" feed, which carried the ambient noise from the players and coaches, and a "crowd noise" feed that would aim to imitate the atmosphere of a packed stadium. In the U.S., fans experienced the artificial crowd noise.

Replicating an atmosphere of fans in a behind-closed-doors match is hard -- Dortmund's stadium routinely sells out its 81,365-capacity seating -- and there is no one solution. As other sports plot their comeback after being postponed because of the coronavirus, the Danish SuperLiga is looking at bringing fans into the stadium via Zoom, while Borussia Monchengladbach offered supporters the chance to have a cardboard cutout version of themselves in the stand.

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So how did Sky Deutschland do it? And will their methods work in different sports? We spoke to Alessandro Reitano, Sky Deutschland's SVP sports production, to find out their process.

ESPN: How does the process work to offer viewers fan noise?

First of all, we're really pleased to know us introducing the sound option has been so well-received worldwide.

For us, it was clear that we want to provide fans with extra options as part of our live broadcasts in order to deliver the best possible experience during this very special situation. The main underlying principle has always been to be respectful to the fans. Like all fans, we miss the support in the stadiums, which cannot be replaced in any way. This is the reason why we decided to put the actual stadium sound on as the basic audio setting and offer an additional second audio track with "stadium atmosphere" for customers.

What we're doing is creating, for every team or match which is played, playing or will be played, a basic audio carpet from [the earlier game between these two teams]. We then created specific audio samples to run over the top.

So, for instance, Dortmund vs. Bayern on Tuesday: we took the basic audio carpet from the last match they played against each other. And let's say what we do then is we have a basic crowd noise of fans, chanting and everything, and we will deliver exactly this part to the outside broadcast (OB) van on-site. Our audio engineer in the OB van is mixing the authentic sound, which is happening at the stadium, together with this audio carpet. We get this feed into our broadcasting center in Unterföhring, near Munich, and now comes the tricky last bit.

We created audio samples for specific scenes: penalties, fouls, decisions from VAR and how people would react. We created samples from the dedicated fans and there is one guy, a Sky sound producer, who is watching the match live. Their job is to insert a specific sample if an action happens.

Let's say, for instance, there's a foul or a penalty, and we have special samples of how fans would react to that, we play it live into the audio mix. That gives a better result than any other way, we feel, at the moment. The whole audio operation is done with up to 10 people across a weekend.

There must be a lot of pressure on the producer, who is manually adding the fan reaction. What happens if they press the wrong button?

There is a lot of responsibility. From our point of view, when we started this project, we said, "OK, we have to do it right with all the respect to the fans." So the sound producers we choose are fans of football and frequently visit stadiums. They're familiar with the fan culture, of how fans react, and they anticipate the actions before they happen. They're doing an awesome job; I think you have to listen really carefully to find any faults.

Do they work off soundboards?

They have a soundboard, a sample machine with specific samples stored on the engine, and they have a couple of buttons in front of them with specific actions ready to play.

There was so much work put in beforehand; it took the guys a lot of time to create the right samples from the right fan groups. You're sensitive to what songs they're singing, and the random yelling. They had to work so hard to get the right samples: they watched tons of matches to get the right samples, and this was all done in the past two weeks.

You take a 90-minute "carpet" of audio: what happens when events, like a goal being scored in the original audio, don't marry with what's happening live on the pitch?

This is a grey zone as you obviously can't predict live sport. You can expect, but never predict. This is where the manual aspect comes in, and the producers can overrule the original audio with a different sample. That's why it's not 100% accurate.

What's happening inside the stadium is not like the NFL, where you have all the parabolic mics and the miked-up players. Now, for the first time you can hear the players shouting, screaming and talking to each other. What we're doing is trying to find the balance between the authentic sound, enhanced with the crowd noise, on top with specific audio samples. It's about finding that right balance.

You cannot anticipate a full 90-minute match, but you can create the best possible audio experience. We are improving from matchday to matchday. We don't know how long games will happen without fans, so we use the time to improve constantly.

What have been the biggest challenges?

There's a lot of pressure to anticipate the game and what happens next. As I said before, it's all about being respectful to the unique fan culture in the stadiums. We're very sensitive to that. There is no technological solution here: it can't be solved by artificial intelligence, but so far we've only had good feedback.

Did you take inspiration from video games that use authentic crowd noise? They include fans booing the referee, along with jeering or cheering long passages of passing.

Absolutely. It was funny as the first time we came together as a team, we said "everyone has to watch a match on [EA Sports game] FIFA 20." This was to get the right tone, right atmosphere and to put us in a good mood. Of course, we couldn't have the audio samples from EA Sports, so we had to create our own. This was in our first meeting, which was back in mid-April, but yes, EA Sports was the benchmark.

There were reports the NFL and NBA are considering using fan audio on their broadcasts. Do you feel this model could be used in other sports?

I truly believe yes, it's possible, and everyone should consider it. The key is to respect the individual fan culture of the specific sports. And if you offer a good solution, it will be appreciatively received.