Reed Birney was beginning to smolder. Every time the actor came on stage as O’Brien, the chief torturer in “1984” at the Hudson Theatre, a group of theatergoers giggled.

“The laughter was inappropriate. I was trying not to take it personally, but it was getting on my nerves,” Birney said of the Oct. 6 incident.

And then he snapped.

During a torture scene when the house lights go up on the audience, Birney stood still, raised his arm and pointed at the clump of gigglers.

“I stared them down,” he said. “But it shut them up.”

Badly behaved audiences are all too common on Broadway. Phones ring, screens glow as people text, wrappers crinkle. And now that theatergoers can drink alcohol during many shows, they fidget, rattle the ice in their cups, nod off and snore, or laugh in all the wrong places.

Many actors object to the drinking, but they have no power over theater owners, who enjoy the fat profits that come from $20 glasses of wine.

“I didn’t get a good look at them,” Birney said of his tormentors, “but they were probably millennials who were drinking. At the Hudson you can take a bucket of Champagne to your seat. We [would] hear the glasses rolling down the aisles. Sometimes I think we’re one step away from dinner theater.”

Actors have adopted different tactics to deal with rude audiences.

During the 2015 run of the comedy “Shows for Days,” Patti LuPone, playing a small-town theater diva, snatched a phone from the hands of a woman who was texting.

Back in 2009, she hollered, “Stop taking pictures now!” during a performance of “Gypsy.”

“I don’t mind people taking my picture if I’m doing a concert,” LuPone told The Post before a performance of her current show, “War Paint.”

“But not when you’re onstage trying to create an atmosphere, trying to help the audience suspend its disbelief. It takes us a long time to get the audience back to the environment we created.”

LuPone’s wrath isn’t confined to her performances. The other day the actress was at “A Bronx Tale,” and a woman kept kicking the back of her seat and texting. After LuPone complained to the house manager, she overheard the woman say about her, “I understand — she’s old.”

At another show, someone got under her skin by unwrapping candy for an eternity. “If you don’t stop with the candy, I’ll kill you,” LuPone told the audience member.

“No one is safe from Patti,” said Birney, laughing.

For him and many other actors, the ideal way to stop bad behavior is to do so in character.

“I don’t think I would have done what I did [at ‘1984’] if that moment with the audience wasn’t built into the play,” said Birney. “I wouldn’t want to stop a show, but my character is already scary to them, so I went full-on weirdo.”

A cellphone went off as Laura Benanti was singing “Will He Like Me” during a performance of the 2015 revival of “She Loves Me.”

“I’ll wait,” she said. The phone continued to ring. “We’ll all wait,” she said, and the orchestra stopped playing until the phone was silenced.

Benanti later tweeted: “Anyone saying I shouldn’t have called out the ringing during my quietest, most vulnerable moment during yesterday’s matinee can suck my phone.”

The most notorious instance of bad behavior took place at “Hand to God” in 2015. Before the show started at the Booth Theatre, a young man climbed on the stage and plugged his phone into an outlet on the set. Several minutes later, as the houselights went down and the cast was waiting in the wings, he jumped back on stage to retrieve the phone.

The cast “freaked out,” a production source recalled.

The outlet was fake, “but he thought his phone was charging the entire time before the show,” said Geneva Carr, one of the leads, who now appears on CBS’s “Bull.” “What a ding-dong! But our crew moved so fast. Five guys in black jumped him. It was a little scary.”

Playbill later identified the offender as Nick Silvestri, a 19-year-old student from Nassau Community College.

Silvestri admitted to having a few drinks before the show, but was unapologetic.

“Girls were calling all day,” he said. “What would you do?”