LOS ANGELES — Imagine you’re a really bad singer. You don’t just miss a note occasionally - you miss almost every note. You sound like a dying goose. But you have no idea how terrible you are because you hear only positive things about your voice.

That’s the plot of “Florence Foster Jenkins,” in which Meryl Streep brings to life the story of an actual 1940s New York socialite who sold out Carnegie Hall despite being an awful singer.

Her husband (Hugh Grant) paid critics to write positive reviews. And her pianist — played with comic elan by “The Big Bang Theory’s” Simon Helberg — attempted to make up for her vocal shortcomings via his musical dexterity.

The role of the pompous but empathetic pianist could be a career changer for Helberg, best known for playing nerdy aerospace engineer Howard Wolowitz on CBS’ long-running sitcom hit.

A few blocks from the Los Feliz home he shares with his wife and two children, the 35-year-old discussed his own reputation in Hollywood, what it was like working opposite the almighty Streep and the lack of respect for multi-cam sitcoms.

Q: One of the themes of the movie is self-image. Do you think most actors in Hollywood have a sense of how they are truly perceived in the industry?

A: I think it depends on the level you’re at and how much money you pay your agents to lie to you. Earlier on, I felt like I got some pretty straightforward feedback from people. When you’re starting out, there’s no incentive to tell you anything but the truth. You’ll get feedback that’s like, “You’re not handsome enough.” They will dress up those things a little bit too by saying, “You’re too character-y,” which means too ugly or too Jewish or too short. Those are hard things to hear. But in the beginning, I was probably more like Florence. Just blind, pure passion.

Q: Say you were in Florence’s position: Would you want to know that everyone actually thought you were a bad actor?

A: I’m sweating. I feel like that’s happened. There’s a part of you that has to care — if you’re trying to tell a story, you want to know if the story got across. Critics are definitely operating in a vacuum and will be brutally honest. I just don’t know if their honest opinion is the honest opinion that I’m craving the most. It’s just that they’re the ones with the loudest voice. If Florence was so passionate about singing, and it brought her such a tremendous amount of joy — telling her that the experience people were having was different than the one that she intended on them having and then she stops pursuing her dream. Is that worth it?

Q: Every actor in the world is so obsessed with Meryl. Having worked with her, do you get why?

A: Aside from this almost divine, supernatural ability that she has — which is ironic, that she is playing someone who is completely free of ability or talent — she also has the most incredible generosity. The most simple way to describe it is that being with her on set, you feel like you’re with someone who sees in 360 degrees.

Q: OK, but she sings so badly in the movie. That must have gotten on your nerves occasionally.

A: What she’s doing is so insanely hard. She was singing literally the most complicated, most well-revered canon of operatic music in four or five languages. And what’s amazing is she was actually singing it kind of well. That’s what makes it so bad. She is coming up right next to the note, or passing through it.

Q: You played jazz piano in high school. Did that help you get the part?

A: When I first met with Stephen (Frears, the director), I was just going in to say, “Hey, I played piano. I can probably play some of these things. But at the very least, I can put my hands exactly where they should be and you can fix it in post.” But by the end of the meeting, I was like, “I’m a professional classical pianist and I can play anything.”

Q: Whoa. So how did you live up to that promise?

A: I rented an apartment to practice the piano and to work, because that’s how scared I was to make this movie. It had a piano, and I had to practice for, like, three or four months. Aside from learning the pieces, it was more about the technique — watching a lot of Vladimir Horowitz and (Arthur) Rubinstein videos seeing how they sat and held themselves.

Q: This year, “The Big Bang Theory” has averaged over 20 million viewers an episode. And yet it doesn’t seem like the show gets talked about as much as, say, “Game of Thrones.”

A: I don’t think Hollywood respects multi-camera television. Well, I don’t think they disrespect it, but I don’t think it gets respect for its artistry. If you’re talking about “Game of Thrones” and “Breaking Bad” and “Transparent” - every episode looks like a film. They are beautifully shot, and they’re making eight or 10 episodes over the course of six months. We shoot for nine months. We make 24 episodes. We shoot one every five days, and we shoot for three hours live in front of an audience.

We are one of the few multi-cams that year after year keeps ending up at the Emmys and the Globes and the SAG Awards. We’re there, which to me is a sign of acclaim. But I think there is something about doing broadcast television on a network at 8 o’clock that is going to have to remove certain elements of grit and nuance and style.