A great racket rises, like a symphony of a thousand hedge trimmers, from the South Lawn of the White House. A shambling pack of men and women — photographers hauling cameras and stepladders, technicians bearing furry boom mics, reporters jostling for position like NBA rebounders — quickly assembles into a bristling knot.

The engines of a Sikorsky helicopter, otherwise known as Marine One, smother attempts at conversation. A soft breeze wafts a cloud of exhaust toward the journalists. It smells like a bus station out here.

The president walks out of the White House and approaches the eager mob. He says something into the boom mics, but this, too, is swallowed by the noise of the grinding machinery.

“Mr. President,” shouts a reporter over the chopper. “[Unintelligible] Turkey . . . Syria . . . Kurds . . . [unintelligible]?”

But Trump isn’t taking questions today, a rarity for him and a disappointment for the journalists. He spins on his heels and heads toward the waiting helicopter. The boom mics slump.

The cumbersome South Lawn “gaggles” — as the president’s chopper meetups are informally known — have become a signature motif for Trump, and they’re among his most frequent engagements with the media. Unlike his irregular Oval Office press “sprays” or the odd news conference, the helicopter encounters are a regularly scheduled event, typically occurring whenever the president heads out of town or comes back into it. Wednesday’s brief helicopter stop-and-talk was the 75th Trump has conducted since taking office, according to Mark Knoller, a CBS News White House correspondent who tracks the president’s media practices.

But a question has always seemed to hover over the ritual: Why?

Why meet the press in the open-air equivalent of an airport departure lounge? The White House has a perfectly nice press briefing room — indoors, climate-controlled, no helicopter noise — but the president prefers to stalk the South Lawn, come heat, humidity, wind, insects or winter’s frost.

“I think it’s nothing more than a matter of efficiency and further accessibility,” says Stephanie ­Grisham, the White House press secretary. “The press are always out there prior to his departure anyway, so it’s natural for him to stop and take questions. . . . It’s not like we call the press to the lawn just so he can talk to them — they’re already there.”

Except that reporters follow the president everywhere they’re permitted and would eagerly assemble for a chance to question the president at any time. So “efficiency” seems like the least of it.

Instead, reporters and others say Trump seems to prefer the freewheeling Q&As because they’re to his advantage. The format is a win-win for Trump, enabling him to grab the spotlight while marginalizing the press, both aurally and visually.

As Wednesday’s brief encounter made clear, even people standing a few feet from the president can’t make out the questions over the chopper’s engines. Trump himself has frequently asked for questions to be repeated. (“You’ve got to talk louder,” he’ll say. . . . “Say again.”) This din acts as a kind of camouflage, reporters say, enabling Trump to ignore questions that he doesn’t like and to move on to those that he’d prefer to answer. “He’d never be able to get away with that in a press conference,” one reporter says as she walks away from the lawn Wednesday.

An idling helicopter also tends to eliminate subtlety and nuance in the questions themselves. Because it’s difficult to communicate much more than a word or phrase with a Sikorsky whirring a few feet away, reporters can’t engage in “grandstanding,” as former White House press secretary Sean Spicer once described the behavior of reporters who go on too long.

Further, the reporters asking questions are barely seen. Unlike formal news conferences, in which there are multiple fixed cameras, journalists haul their own cameras to the South Lawn. This limits the number of “cutaway” shots — secondary pictures designed to break up a continuous image — and keeps the focus squarely on Trump.

The setup also frees Trump from being hemmed in by a lectern or a chair when he’s taking questions. He usually paces up and down the press line on the South Lawn, calling on reporters at random, answering rapidly and then moving on to the next shouted question. His freedom of movement closes off follow-up questions or skeptical rebuttals.

In all, the chopper gaggles are “a dominance ritual,” says Todd Gitlin, a professor at the Columbia School of Journalism. “It’s set up to make him look like he’s in command, and he’s lording it over [the news media].” Even the name — “gaggle” — suggests something demeaning, notes Gitlin: “You’re a bunch of geese, and you’re eating out of his hand.”

In the absence of daily press briefings, the helicopter gaggles provide limited access to the president and news about him, says Frank Sesno, a former CNN anchor and White House correspondent who directs the media and public affairs program at George Washington University. But for the most part, he says, they are “little more than presidential spin cycles. . . . He is not there to answer detailed, nuanced or tough questions. Instead, we have the president playing press secretary on his turf and terms. And he gets mileage from these things.”

Perhaps more than any other reporter, former ABC News White House correspondent Sam Donaldson knows how this game is played. Donaldson famously shouted questions at President Ronald Reagan as the commander in chief strained to hear — or feigned straining to hear — over Marine One’s engines, too.

But Donaldson says Trump’s chopper Q&As are wholly different from Reagan’s, both in number and kind.

“My observation is that Trump sees it as easy way out of holding a press conference,” he says. “It’s not a press conference in any accepted sense that we had in the past. It’s just another way for him to limit the press.”

But Donaldson expresses a kind of grudging admiration for the strategy. Trump, he says, “commands the scene imperially. I know his base loves it. He’s like a lion tamer out there. If he had a whip and a chair he’d be” a Las Vegas performer.

Given limited options, White House correspondents eagerly scramble to cover Trump’s South Lawn appearances, sometimes leading to disorderly scenes. “Don’t run!” several people called as the Secret Service led a long line of journalists through the West Wing and out past the Rose Garden for Trump’s truncated appearance Wednesday.

The chaos — all that equipment, all those bodies — prompted the White House Correspondents’ Association to step in last month in an attempt to keep order.

The organization distributed guidelines to its members spelling out their marching order, literally, for assembling on the lawn. Pool TV cameras, for instance, are in “wave 1,” while “guests or interns in a non-newsgathering capacity” take up the rear in “wave 4.” There’s also a list of dos and don’ts. (Reporters are advised not to bring “ladders, step-stools, selfie-sticks, tripods or boom-mics,” these being reserved for working photographers and TV camera crews.)

Jonathan Karl, the WHCA’s president and a veteran correspondent for ABC News, says the guidelines have helped streamline the process, at least somewhat.

“As far as I’m concerned, the more opportunities reporters have to ask questions of the president, any president, the better,” Karl says. But he adds that the South Lawn “availabilities” are no substitute for formal news conferences and regular White House briefings.