Question: Who voiced Howard's never seen mother?
About the article "The Big Bang Theory", section "Howard's mother".

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In scenes set at Howard's home in which he interacts with his never-seen mother (voiced by Carol Ann Susi), he always does so via shouting conversations between the rooms in his house, and she similarly interacts with other characters in this manner, though she did appear momentarily in the overhead photo of Howard and Bernadette's wedding and from the side in "The Spoiler Alert Segmentation" episode, though her face was not shown.
She reflects the Jewish mother stereotype in some ways, such as being overly controlling of Howard's adult life and sometimes trying to make him feel guilty about causing her trouble.
She is dependent on Howard, as she requires him to help her with her wig and makeup in the morning.
Howard in turn is attached to his mother to the point where she still cuts his meat for him, takes him to the dentist, does his laundry and "grounds" him when he returns home after briefly moving out.
Until Howard's marriage to Bernadette in the fifth season finale, Howard's former living situation led Leonard's psychiatrist mother to speculate that he may suffer from some type of pathology, and Sheldon to refer to their relationship as Oedipal.
Her tendency to communicate with Howard by shouting between rooms has led Bernadette and Raj to do impressions of her, and Bernadette to attempt to communicate with her in one episode by imitating her style of shouting.
Until his marriage, Howard was noted for still living with his overbearing mother, who is selectively oblivious to his accomplishments as an adult and usually treats him like he is still a child, filling the cliché of a Jewish mother.
Once, Leonard stated that Howard "was in a pretty serious relationship-with his mom."
Howard is an only child.
Howard's wife is Bernadette Rostenkowski-Wolowitz.
Wolowitz (voiced by Carol Ann Susi) is not shown on-screen until the season 6 episode "The Spoiler Alert Segmentation", but her voice is heard when he is at their house or when he talks to her on the phone.
She only communicates with Howard by yelling to him in an obnoxious manner, which results in awkward long-distance conversations, with Howard yelling back at her in a frustrated manner.
Her nosy nature and her barrage of questions make Howard's life tense at home, which prompts him to call her a "crazy old lady".
It is revealed in "The Cohabitation Formulation", however, when Howard briefly moves in with Bernadette, that he likes being "mothered" to some extent.
In "The Apology Insufficiency", Sheldon observes that Howard seems to have "an unresolved Oedipus complex".
In "The Precious Fragmentation", Howard reveals that his father left his family when Howard was eleven years old.
His mother bought him an ALF doll to help Howard try to get over it.
When Howard finds a similar doll at a garage sale, he starts talking to it as if he were eleven again, asking him to find his father and bring him home.
This causes Penny (who usually avoids Howard and is disgusted by him) to be sympathetic.
The trauma of his father's desertion and the lack of a father figure throughout adolescence may be the root of much of Howard's behavior.
So far Howard is the only character out of the main cast who has never had a family relative appear on-screen but his family seems to be rather extensive and distributed all over the USA, as seen from the time when he briefly dated Dr. Stephanie Barnett.
In "The Shiny Trinket Maneuver", it is mentioned that the birthday party where he did his magic show was his cousin's party but it is unknown who his cousin was in the group of children that were present.
In "The Closet Reconfiguration" Howard gets a letter from his father which is the first contact that he gets from his father in the show. 
Bosgun is voiced by who also voiced High Priest Darom as seen above. 
A detective cat named Super Snooper (voiced by Daws Butler impersonating Ed Gardner as the character Archie from the radio show Duffy's Tavern) and his sidekick Blabber Mouse (voiced by Daws Butler, originally voiced by Los Angeles radio announcer Elliot Field).
In several cartoons, they had a private secretary named Hazel (voiced by Jean Vander Pyl), who was never seen on screen. 
Mrs. Wolowitz (voiced by Carol Ann Susi): Howard's controlling, belittling Jewish mother.
The character is not shown on-screen with the exception of one episode in season 6 in which her body, but not face is briefly shown.
Mrs. Wolowitz's raspy voice is heard usually in scenes at her house, which she shares with Howard.
She talks to Howard always by yelling at him from another room, which results in awkward conversations with Howard yelling back at her.
In an early episode, when the guys hear her yelling in a masculine voice, they ask Howard if that was his father, to which Howard replies "If she grows any more hair on her face, yes".
She is also described as being enormously obese (especially in the arms), and wearing a wig and painted-on eyebrows.
Mrs. Wolowitz seems to be oblivious about Howard's work as an engineer and treats him like he is still a child.
She frequently refers to Leonard, Sheldon, and Raj as Howard's "little friends" (as in, "I made some cookies and Hawaiian Punch for you and your little friends!")
and often refers to Caltech as a "school".
Howard often makes references to his mother as being a "crazy old lady", but deep down, he is deeply attached to his mother and quite happy to be treated like a child.
However, in one episode, Howard attempts to move out after a fight with his mother, but has serious delusions that she is trying to force him to stay, when in actuality, she is urging him to move out, which leads to him staying.
In the penultimate episode of season 4, she wants to "play doctor" with Raj when he asks to sleep over.
When Howard reveals that he has proposed to Bernadette and she has accepted, she collapses, causing Howard to panic (and dislocate his shoulder while trying to barge into the bathroom to help her).
The timing leads him to believe that she may not like Bernadette (who is Catholic) and has suffered a heart attack from the shock of the news.
In actuality, her fainting was due to food poisoning from the food she ate while meeting Bernadette, and was completely unrelated to Howard's news.
She has graciously accepted Bernadette as her future daughter-in-law and loves that she is a doctor.
She attended Howard and Bernadette's wedding on Leonard/Sheldon/Penny's apartment building roof and can be seen in the satellite picture of the event.
The episode "The Spoiler Alert Segmentation" is a major episode in Mrs. Wolowitz's character as she appears on screen for the first time; first walking across the kitchen through the kitchen doors, and then her hands are seen pulling Raj back into the house.
Her face is not seen at all, but her appearances in the kitchen scene make her out to be an extremely obese woman.
It is often implied that the relationship between Howard and his mother comes close to that of Norman Bates and his mother from the film "Psycho".
She was the court clerk that came out to tell the wedding party that the judge could not marry them.