Most human beings cannot scream for ten minutes straight without ripping up their vocal cords or running out of oxygen. And if that sounds bad, imagine doing this multiple times in a row. This is why it seems plausible to believe that the voice actors for Dragon Ball Z might've strained their bodies trying to perform the over-the-top shouting the series required.
When rumors broke that Sean Schemmel, the voice actor of Goku for the FUNimation dub of Dragon Ball Z, passed out when recording the screams for Goku's Super Saiyan 3 transformation, the infamous intensity of the performance made it ring true with fans. However, Schemmel has more than once clarified that he never passed out while recording for Dragon Ball Z. However, that doesn't mean it hasn't happened during his many years playing Goku.
The Origin of the Rumor
The Super Saiyan 3 transformation takes place during Dragon Ball Z's Buu Arc, where Goku achieves a form beyond Super Saiyan 2, unleashing a scream so mighty and powerful that it literally rocks the entire planet. The screams in the English dub are sustained for a substantial amount of time and almost sound like they're tearing up Schemmel's vocal cords just to produce.
Many suspected that the intensity of the scream physically harmed Schemmel in some way. These rumors were further substantiated when fans at conventions claimed they heard Schemmel or other FUNimation voice actors mention that Schemmel passed out playing Goku at some point during the series. Many fans argued it had to be either when Goku first transformed into Super Saiyan 3 or when Schemmel recorded his Super Saiyan 3 scream for the 12th Dragon Ball Z film, Fusion Reborn.
However, while this rumor spread like wildfire, no one could really cite the source from where it originated. Or, at least, no material source. Fans would instead say they heard it at a convention once without being able to pin down where, made worse by convention-goers only half-hearing Schemmel explain what happened, leading to more circulating falsehoods.
The Real Story
While Schemmel has clarified this story in the past, a video recorded at 2012's London Film & Comic-Con spread the story of Schemmel's fainting spell while recording Goku to a wider audience in full detail without a game of fandom phone tag muddying his message.
Here's what Schemmel had to say in response to a question on the subject from an audience member:
"Here's the deal: I never, ever passed out in Dragon Ball Z, but I did pass out in Dragon Ball GT. GT, not Z. And it was during the Super Saiyan 4 transformation and I was really tired...and I had been working, not sleeping well. And I miscalculated the amount of air you need for a Kamehameha, I think -- or maybe it was a power up -- and I made the voice lower. So, if you get lower when you're acting, the aperture of your vocal cords gets wider, and I just totally miscalculated."
Schemmel went on to clarified that he passed out for a few seconds in the booth, bumped his head, but went right back to it after resting. He clarified that because he didn't have to lower his voice for the Super Saiyan 3 transformation, he had a lot less difficulty doing that particular scream, even finding the time to do a Bon Jovi impersonation as an outtake for fun.
Schemmel, in the clip above, suspects that part of the inaccuracy in the rumor has something to do with how long and sustained the scream was. "I think it's because the Super Saiyan 3 was so long, so they [say] 'Oh, you must've passed out then.' But that was easy because it was higher and you're putting a lot of air through a smaller tube, so that's easy to do. That won't make you pass out... but when you exhale and don't get enough oxygen, that's when you pass out, especially if you haven't slept in a few days."
Nevertheless, the rumor that Schemmel passed out while recording Super Saiyan 3 is still believable enough to continue spreading to this day, despite video evidence to the contrary.