Starting this season, Major League Baseball umpires will use a microphone to announce decisions made by the replay booth, the league announced Friday.  
MLB says that training has been held in Arizona and Florida this spring in anticipation of Thursday’s season openers. 
Until now, umpires had revealed their decisions such as safe and out with hand signals.
MLB expanded replay review in 2014 to include challenges from managers. Previously, video review was only used for boundary calls on home runs — initiated at the discretion of umpires.
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According to reports, the rule was to be implemented during the 2020 season, which was halted and later reduced to 60 games because of the coronavirus pandemic.
The decision to audibly announce calls by umpires follows other sports that have been using technology for years in allowing their officials to announce penalties, scoring decisions or coaches challenges to help viewers at home and fans at the games understand the game better. 
The NFL has been putting a wireless microphone on the referee for penalty announcements since 1975 and became a vital part of the game once the league reintroduced instant replay in 1999.
The NBA has used public address announcers to relay decisions in games, and during telecasts, an official is seen on camera to announce decisions.
NHL referees were equipped with microphones to announce penalty calls at the start of the 2005 season, and their scope widened with coaches’ challenges that began in 2015.

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