He added, “Something like that is just slow. I mean pop – blow your eardrum out — I don’t even know how that happens. But I don’t know how it heals either. But, she says she can hear now. She’ll be all right.”
Stefani, 47, was forced to pull out of a Las Vegas performance after the injury. A source told PEOPLE at the time that although Stefani sought medical attention at Cedars-Sinai Medical Center in Los Angeles, she wasn’t admitted.
Shelton, 40, told ET that Stefani’s injury happened when she boarded an airplane with a head cold. Her ear ruptured “once she got up to a certain altitude,” he explained.
RELATED VIDEO: Inside Blake Shelton and Gwen Stefani’s Relationship: ‘Their Chemistry Is Undeniable’
“She’s singing tomorrow,” Shelton added, referencing Tuesday’s live episode of The Voice. “She’s doing good. She’s tough.”