A clueless audience member at David Mamet’s Broadway flop “The Anarchist” made the ill-fated show an even more miserable experience this week.

Sources who endured the play — which stars Patti LuPone and Debra Winger and is closing early after lethal reviews — say an elderly theatergoer accidentally interrupted the performance when he tried to make an experimental hearing aid out of his iPhone.

“The hearing aids that they give out to people weren’t working,” explained our spy who attended the show earlier in the week. “So there was an older gentleman who started trying to use an app on his cellphone as a hearing aid. And it started to interfere with the sound at the show.”

The result, the source said — recreating the sound for us with annoying precision over the phone — was a nerve-jangling “Eeeeeeeeeeeeeeeeeee!”

Soon, the rest of the annoyed audience began to rebel. “They were all telling the guy to shut up,” our source says. After 20 minutes of the intermittent feedback, the man and a woman companion left the theater.

“The audience would have stood up and applauded when they finally left, if they could have,” sniffed the source. It wasn’t the worst news for Mamet’s latest play this week: After opening last Sunday at the John Golden Theater, it was announced Tuesday that it would close on Dec. 16 after just 17 regular performances.

The play follows LuPone and Winger as an imprisoned leftist radical and a prison official.

Post critic Elisabeth Vincentelli said the “writing [is] repetitive and blunt” and “falls short of the lofty aspirations.” Other reviews called it “dull and virtually without drama” and a “brittle, stripped-down debate-club exercise.”

Though our source says LuPone and Winger were wonderful, perhaps the audience was lucky they couldn’t hear every word after all. Meanwhile, a revival of Mamet’s “Glengarry Glen Ross” starring Al Pacino is at the Gerald Schoenfeld Theater on the same block.