Gary Oldman: Depends. Do you promise to keep this version of your Batman voice and never change it to something completely indecipherable?
Bale: I promise no such thing.
A character changes voice while in costume. It is usually part of an attempt to disguise themselves. The voice change may be done by themselves, or done via external means, such as a mask or helmet with built in voice modulator. More extreme cases may have a second voice actor Cast as a Mask to provide it.
This is distinct from the more appearance-oriented Clark Kenting. This is an effective way to maintain a Secret Identity and it can also suggest a case of Secret Identity Identity if you consider that the person's two identities have totally different voices and mannerisms.
- Hei of Darker Than Black has his voice deepen when he goes from his persona as Li into his identity as the "Black Reaper". It's not for nothing they call him Chinese Electric Batman.
- Lelouch from Code Geass speaks with his regular teenager voice when in his civilian, Rich Idiot With No Day Job persona, but switches to a much deeper, booming (read: much more epic) voice when acting as the Rebel Leader Zero.
- Shuichi Akai from Detective Conan, was supposedly killed by Kir on orders from the Black Organization, only to resurface under the alias of Subaru Okiya, with a voice changing choker underneath his turtleneck sweater to alter his distinctive voice, even played by a different voice actor to complete the masquerade.
- All Might from My Hero Academia speaks in a booming and enthusiastic voice fit for a superhero; as civilian Toshinori Yagi, he sounds tired and deadpan. This has less to do with preserving a secret identity and more to do with keeping up his image as the tireless symbol of peace and justice.
- Sword Art Online: In the anime adaptation of the Phantom Bullet arc, the normally shy Shino speaks in a slightly deeper, rougher voice when in-game as the Cold Sniper Sinon. Meanwhile the Dude Looks Like a Lady avatar that Kirito receives in this arc initially distorts his voice into a falsetto, but it's forgotten as the story gets more serious. In addition, Death Gun wears a mask that deepens and distorts his voice. This helps conceal the fact that "Death Gun" is actually a shared identity. When Death Gun first appears, his manner of speaking is highly dramatic due to him being controlled by the young and impulsive Kyoji Shinkawa; but when Kirito encounters him later, his cadence is much softer and calmer, since he is controlled by the more experienced elder brother Shouichi.
- In the spinoff Sword Art Online: Alternative Gun Gale Online, a number of characters have higher or lower voices in-game due to using avatars with a vastly different body type from their own, with one exception of Miyu who keeps her real life voice and mannerism when playing her small-sized avatar Fukaziroh.
- In Dragon Ball Z, Son Gohan puts on a fake superhero voice when he is disguised as the Great Saiyaman.
- Umaru from Himouto! Umaru-chan changes her voice between her "outside" and "inside" personas. She sounds like a mature and proper teenage girl while "outside" in public, while in private her voice is more high-pitched and childish to reflect how she's really an immature Closet Geek.
- Superman: Most versions of the character, starting with the 1940s radio serials but most famously in the adaptation mentioned in Film below, speak very differently as Kal-El than as Clark Kent: Generally he pitches the latter's voice slightly higher and affects a mild stammer, and sometimes hams up his Kansas farm-boy accent a bit, as well as altering his posture and body language to make himself seem smaller and less confident. Occasionally this is attributed to some sort of minor superpower involving "precise muscle control" or even low-key psychic powers, Depending on the Writer and continuity, but most versions explain it as Clark simply being a talented actor.
- Parodied in The Simpsons comics where Milhouse takes up the Bartman mantle after Bart quit due to a smear campaign and he talks about using "that dark, raspy voice that makes him sound like on of [Bart's] aunts."
- In Superman: The Movie, Clark Kent has a distinctively weaker and higher pitched voice and a very different, more wishy-washy speech pattern than Superman does. This is most noticeable in a scene where he is considering confessing to Lois that he is Superman, but chickens out at the last second and resumes his weaker persona.
- In Batman v Superman: Dawn of Justice, Batman uses an electronic voice modulator to alter his voice.
- The Dark Knight Trilogy
- The deepening of Bruce Wayne's voice when he puts on the Batman costume is taken Up to Eleven- he sounds like he's gargling with gravel. Oddly, he still does this even when he's talking to people as Batman who know his secret identity.
- He takes this to another level in Batman Begins where he has his normal Bruce Wayne voice, a raspy voice for talking to allies as Batman, and the gravel-gargling voice he uses when trying to scare the crap out of bad guys.
- In Green Lantern, Ryan Reynolds as Hal Jordan plays with this a bit - speaking in his dramatic superhero voice when trying to impress Carol Ferris as Green Lantern, but she soon sees through this.
Carol: I've seen you NAKED! Did you think I wouldn't recognize you because you covered up your cheekbones?!
- Iron Man: Stark's Iron Man armor's helmet makes his voice more mechanical.
- In On Her Majesty's Secret Service, in the scenes where Bond is impersonating an expert on heraldry George Lazenby is dubbed by the actor who played the real expert.
- Parodied in Spider-Man: Homecoming, where Peter Parker's suit (also made by Stark)'s "Enhanced Interrogation Mode" gives the bumbling teenager's voice a comically deep filter. And he also tries to affect a Brooklyn Rage accent when saving his classmates.
- Senator Palpatine/Darth Sidious in Star Wars. Palpatine loses the "normal" voice entirely after Mace Windu's attack, when he becomes Emperor.
- Royal Pain from Sky High (2005) speaks with the, slightly processed, voice of Patrick Warburton whenever the elaborate mask is in place to preserve The Reveal that "he" is actually Gwen Grayson, played by Mary Elizabeth Winstead who uses her own voice after removing the mask.
- Harry Harrison's "The Fourth Law of Robotics": The surveillance cameras record the bank robber as having a very feminine voice. Donovan points out that since robot voice simulators are used for all robots, changing one out for bass or soprano is easy enough. It is one of the clues he uses to prove the robber must have been a robot.
- The Arrow himself uses a voice modulator that artificially deepens his voice that not only keeps people from recognizing his celebrity voice, but also works to intimidate thugs suddenly faced with a murderous and guttural archer.
- The Smallville version has this too.
- Sara Lance uses a voice modulator similar to the Arrow's to prevent people from identifying her as the Canary.
- The Flash (2014): Whenever Barry Allen needs to talk to his crush as the Flash, he vibrates his vocal cords at super speed so she won't be able to recognize his voice. His Evil Counterparts, Reverse Flash, Zoom, and Savitar all use this technique to alter their voices, but they end up deepening their voices so much that people mistake them for demons. (The Rival also does this, but its less ominous-sounding, more akin to the Barry version.)
- Zoom, Savitar, and Godspeed also use different voice actors when in costume. This is mainly done to hide the identity of the speedster from the audience. For example, Zoom is voiced by Tony Todd in costume, Savitar's costume voice is done by Tobin Bell, and Godspeed in costume is voiced by B.D. Wong.
- Batwoman (2019): In the reverse of the standard where the heroic person has a more gutteral voice, Kate Kane has a noticeable vocal fry whereas Batwoman tends to speak without it.
- In the Batman (1966) television series, Bruce Wayne was put into a situation involving him Holding Both Sides of the Conversation. Since he's on a phoneline, it's just a simple matter of switching between his Batman voice and his Bruce voice.
- Black Lightning: Pierce gives his voice a reverb effect when he's in the suit. Jennifer also mentions that his face "hurt to look at," further helping obscure his identity, though his face doesn't look any different to the audience.
- Daredevil (2015): Matt Murdock has a change of cadence to his voice when he is costumed up as Daredevil. As himself in public, Matt has a jovial, easy going cadence, even in court. When in costume, he is much more terse and direct, which is noticeably different.
- Hunter Street: When disguised as HoodieHead, Sophie has a vocal modulator to change her voice to be unrecognizable.
- In Choujinki Metalder, Tsurugi has a completely different voice actor for when hes transformed. In the final episode, its a Bittersweet Ending where he loses his powers but cant return to his human form ever again, and Metalder speaking with the Tsurugi voice now really hammers it in.
- In Power Rangers, a few mystery Rangers have had deeper voices that disguised their secret identities. The first was the original Gold Ranger in Zeo, who had a different voice actor when morphed.
- Kamen Rider Fourze does it better than any of the above, making for a hell of a Reveal: youd never guess from the deep growly voice of one of the Big Bads generals (that one being Scorpion) that hes actually a she (aka Sarina Sonoda, the mild-mannered Nice Girl teacher) and was right under the heroes noses all along.
- From the same series, Virgo is assumed to be a female, with the womanly voice to match thanks to Rie Tanaka. Come episode 42, and it's revealed that she is actually a he - Kuniteru Emoto aka Tachibana to be precise.
- The Masked Singer uses synthesizers to pitch up the disguised contestants' speaking voices.
- In Batman: Arkham Knight, the titular Knight uses an electronic voice modulator to distort his normal voice. Given that Batman would recognize Jason's voice otherwise, it does its job well.
- In Batman: The Telltale Series, Batman, himself, uses an electronic voice modulator to deepen his voice. The leader of the Children of Arkham uses a mask with a modulator, as well, to conceal their true identity as Vicki Vale.
- BlazBlue: Hakumen wears a full-body armor and a deep, echoing voice courtesy of the armor. His voice is actually much softer, courtesy of him being an alternate timeline Jin Kisaragi.
- In Fire Emblem: Three Houses, the helmets of the Flame Emperor and Death Knight alter their voices, making them menacingly deep, to conceal their true identities as Edelgard and Jeritza.
- Done by two characters in The Legend of Heroes: Trails of Cold Steel: "C" wears a helmet that modulates his voice, disguising his true identity of Crow, and Thomas notably adopts a deeper, more serious tone when he drops his facade of being a carefree, lackadaisical teacher and reveals he's actually the Second Dominion of the Gralsritter.
- Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy: Cesar Chance's voice is quite nasally normally, but as Ratman, he has a Badass Baritone. Shown in most adorable fashion when he's taking care of his newborn baby.
Chance: Make way, make way! Here comes (turns on the Badass Baritone) Ratman, to save the day.
- Ratchet & Clank
- In Ratchet & Clank: Going Commando, the Thief sounds like a digitally distorted man while wearing their costume, but she has a regular-sounding female voice once the costume is off.
- In Ratchet & Clank Future: A Crack In Time, at one point, Ratchet pretends to be Dr. Nefarious in order to use the laser in his space station to destroy his fleet of ships. This disguise, of course, comes with that character's voice.
- In Dumbing of Age, whenever Amber changes into her Amazi-Girl disguise, her voice gets noticeably more gravelly, which is signified by the normally black text on white becoming white text on blue. Interestingly, while Amber has a split-personality disorder, the vocal shift doesn't necessarily reflect that — her Amber personality can use the Amazi-Girl voice if required and vice versa.
- In Batman: The Animated Series, Batman has a lower, more serious voice than Bruce Wayne. The shift is far more subtle than in the Nolan films, but he seems to put it on whenever he puts the suit on, even when he's talking to people who know he is Bruce Wayne. However, from The New Batman Adventures onward in the DCAU, Bruce's voice shifted down to sound more like Batman than it used to.
- Just like the original Batman, in Batman Beyond Terry's voice also changes in when he's in the bat-suit, though it's explained to be something the suit actually does somehow to help disguise his identity.
- Also from DCAU, the Batwoman in Batman: Mystery of the Batwoman has a voice unlike her real identity, that is, any one of the three. This overlaps with Cast as a Mask as the Batwoman has a voice actress that doesn't voice any of the other characters.
- Big Hero 6: The Series: Hiro puts on a deeper, more "heroic" voice only when saving people who would logically recognizes his voice, such as Aunt Cass or Karmi. He has no problem with using his normal voice when talking to supervillains.
- In DuckTales (1987), Fenton Crackshell is a nebbishy accountant with a voice to match, but when he puts on the Gizmo Duck costume, he becomes The Cape and starts talking in stock hero speak.
- On He-Man and the Masters of the Universe (1983), He-Man, and later She-Ra, have deeper, more resonant, voices than they do as Adam and Adora. Which is probably the biggest difference between their superhero identities and their everyday ones, since otherwise they look almost exactly the same.
- Parodied by Buttercup in The Powerpuff Girls episode where they decide that they all need secret identities to be "real" superheroes. The "Mange" persona she adopts takes her Tomboyish Voice and makes it so raspy it's ridiculous.
- The Spectacular Spider-Man
- Quentin Beck is a fairly mild-mannered guy, and talks in a hammy faux-British accent when being Mysterio.
- The Green Goblin has a personality so different from his civilian identity that it is appropriately represented by giving the two separate voice actors. Interestingly, this version of the Goblin isn't a Split Personality.
- In the 1960s Spider-Man series, Spider-Man's speaking voice is about an octave deeper than Peter Parker's, even when there's no need for it (e.g., when he's talking to himself and there's nobody else around).
- In South Park, Kenny deepens his voice when dressed as Mysterion.
- Wander over Yonder: When Wander becomes a Batman-esque superhero in "The Boy Wander", his high-pitched southern simpleton voice suddenly becomes deeper, husky and more serious.