The high-pitched screaming was more than just a gag.
The Big Bang Theory has a lot of surreal things going on. Almost every conversation the four main nerds had was something you would never hear anywhere but on this show. There were also a lot of long-running funny gags. For example, Sheldon’s inability to understand what sarcasm is, or Raj’s femininity.
Although these gags were mostly invented for comedic relief, they still served other purposes. For example, Melissa Rauch’s voice as Bernadette is one of the character’s most recognizable traits. But it’s more important to The Big Bang Theory than just a joke.
As with many other sitcoms, The Big Bang Theory tried to give each of its cast members distinct personalities and traits. Like Raj’s inability to talk to women, or Sheldon’s “Bazinga!”, or Leonard’s lactose intolerance.
And Bernadette’s trait became her voice, even though she actually used a fake one on the show. The thing is, Rauch was inspired by the way her mother spoke. So even before the audition, she decided she needed something to stand out, and her mother’s voice turned out to be just what she needed.
Her approach paid off, and she was hired as a recurring guest star on The Big Bang Theory, but later CBS decided to make her a regular character because she was so well received by fans.
After some time, when she met Howard and started to build a relationship with him, Bernadette’s voice changed a bit. Well, it was still high and squeaky, but sometimes she put a little extra power into it to sound exactly like… Mrs. Wolowitz.
The similarity in their voices started out as a joke to bring the women closer together, but after the actress who voiced Howard’s mother tragically passed away, it was decided to keep Bernadette’s voice close to Mrs. Wolowitz’s.