The 41-year-old actor lends his voice to the iconic superhero in animation 'Son of Batman' and was worried about how he was going to do the character justice.
He said: "I just didn't want to mess it up, to be honest with you. It's celebrating 75 years of Batman. We've had so many great actors play it so well, over the years, in film, on television, and through voice work, that I just didn't want to completely humiliate myself."
O'Mara experimented with different voice types to try and find something that would "work" before he settled on what he used.
Talking to collider.com, he said: "So, when I talked to [voice director] Andrea Romano about how to find this Batman voice, it was really about finding something that was authentic, but also was unique to me. I didn't want to cover ground that had already been covered, so it took awhile. It's like writing a song. You do one version and go, 'Oh, that sounds like someone else, or something else.' And then, you do another version and go, 'No, I'm forcing that. I'm pushing that.' And so, you try to come across something where you can go, 'Yeah, that could work.'"