Michael Phelps, laughing on the medal stand. (Via NBC)

One of the noisiest yet most beloved traditions in Baltimore (and sometimes Washington) sports made its way to Rio on Tuesday night, and then to NBC’s national Olympics audience, and then to social media, thanks to Michael Phelps and his friends.

Phelps, a proud Baltimorean, had just notched his 20th 21st Olympic gold medal with a narrow win in the 200-meter butterfly. He appeared emotional on the subsequent medal stand, which shouldn’t have been surprising. The 31-year old, competing in his fifth Olympics, is adding to his legacy each time he wins, and this dramatic victory seemed an appropriate moment for deep thoughts.

But then he started laughing.

“My boys from Baltimore were down at the other end,” Phelps explained to NBC’s Michele Tafoya later in the night, after he’d picked up his 21st gold. “And back in Maryland, we all say ‘Oh!’ for the Orioles during that part of the National Anthem.”

Now, this is a tradition familiar to anyone who’s been not just to an Orioles game, but to a Ravens game, or a Capitals game, or a Redskins game, or a Terrapins game, or an early-vintage Nationals game, or any number of other local sporting events. For decades, local fans have joined together on a raucous “Oh!‘ near the end of the anthem. (“Oh! say does that star-spangled banner yet wave.”)

This has prompted periodic debates about whether such screams are an unpatriotic disruption to the anthem, and about whether such screams are merely a Baltimore tradition or should also be employed in Washington, and about whether it’s a tradition that’s run its course.

Phelps, though, clearly approved.

“And all of a sudden I hear them ROAR ‘Oh!,’ and I knew exactly where it came from, and I just lost it,” he told Tafoya. “Because those guys came down from Baltimore and New York City to be here, and it’s just special to see those guys in the stands.”

He wasn’t the only one who approved.