Throughout the 2012 Olympic Games, it was hard to find Michael Phelps without his headphones on his head.

At the time, Phelps didn't have a deal with the brand he was sporting, Sol Republic.

That all changed on Tuesday afternoon, as the consumer electronics company signed Phelps to an endorsement deal.

"He absolutely loves this brand," said his agent Peter Carlisle. "I mean, he was wearing them anyway."

As part of the deal, Sol will begin selling Phelps-inspired headphones on its eBay store on Tuesday, in addition to auctioning off 21 of the headphones Phelps wore before his Olympic races. The proceeds of the auction will go to the Michael Phelps Foundation.

Phelps, who finished his Olympic career with a record 22 medals, 18 of which were gold, has been known to listen to music to pump him up.

And even though he wore Bose headphones at the 2004 games and white Apple headphones in 2008, he never signed a deal with those companies.

Throughout the games, Phelps changed up headphones before each race, but what remained constant was the brand name on his ears: Sol.

Without a deal at the time, he garnered great exposure for the brand, until the last few races when the International Olympic Committee made him cover up the name with tape.

Phelps is keeping quite busy in his retirement. The 27-year-old will be the next student of golf instructor Hank Haney on his Golf Channel Show, "The Haney Project."

Phelps' endorsement deals include Hilton, Hewlett Packard, Omega watches, Head & Shoulders, PureSport drink, Under Armour, Speedo, Subway and Visa. He also has his own video game made by 505 Games and his own lap pool made by Master Spas.