It's literally an echo chamber. "Echo chamber" is usually figurative. Here are some examples from the NYT archive which I've bunched up, without links:
Americans Attracted to ISIS Find an ‘Echo Chamber’ on Social Media... the bars, restaurants and other haunts of entrepreneurs can be an echo chamber... The Trouble With the Echo Chamber Online... “We’ve seen too many Republicans who live in the echo chamber of the mainstream media bubble,” Mr. Cruz said.... [Supreme Court Justice Antonin Scalia] confessed—not in so many words—to living in a conservative echo chamber... With his us vs. them invective and his refusal to denounce hate-filled speech from some of his supporters, Mr. Trump is an echo chamber for certain corners of the far right, as evinced by his popularity with white nationalists and the so-called alt-right movement of mostly online activists.... But CNN may be setting up an echo chamber as it covers bloggers who are blogging about what they are watching on CNN....Also in the NYT, I ran across a piece about an art project by Harry Shearer called "The Silent Echo Chamber" — "video of celebrities and politicians sitting silently in the minutes before appearing live on television."
Video loops run on nine flat-screen monitors that are hung like portraits along three walls. There is a disquieting sense of being at the wrong end of the telescope: the stars you have watched silently for years are silently watching you.... Confronted with silence, whether from a Pinteresque pause or an unreturned “good morning” from that smoldering Irene in sales, we tend to invent an explanation, and it’s no different here. Why, one wonders in the glow of the screens, aren’t these pundits pontificating?That was back in December 2008. There were 4 examples, including this, of Hillary Clinton.