Just a cheer, boo, or drop of a bottle cap in the crowd at an esports event can put a pro gamer off their game and in the worst-case scenario that could cost them the tournament. To avoid that happening, pro gamers wear two headphones: an inner pair that outputs the game audio and another that covers the outside of their ears and blocks ambient noise. Additionally, many tournament rules make wearing two headsets at once compulsory to avoid players obtaining any kind of information advantage from the crowd—basically this is considered cheating.