NEW YORK >> The seeds of Denver’s stunning Super Bowl self-destruction were planted during Wednesday’s practice when coach John Fox decided to turn down the speakers that simulate crowd noise because “it’s not an away game.”

A silent snap count would have been so much better because Seattle’s famed 12th Man showed up on Denver’s first play from scrimmage and helped ruin whatever great game plan offensive coordinator Adam Gase and Peyton Manning had come up with.

Instead of thwarting the Seahawks’ stingy secondary and stout front seven, the Broncos fell apart.

MetLife Stadium might not have been as loud as CenturyLink Field, but it was plenty spirited as the start of all Super Bowls are and when Manning lined up in the shotgun and called for the ball from his 14-yard line, his center couldn’t hear the cadence.

Manny Ramirez crouched still and just as Manning stepped up to reset the play, Ramirez’s snap sailed into the north end zone, where running back Knowshon Moreno smothered it for a safety.

“None of us heard the snap count,” Ramirez said. “I thought I did and when I snapped it, I guess Peyton was actually trying to walk up to me at the time. I’m not 100 percent sure. It’s unfortunate things didn’t go as planned.”

“Nobody’s fault,” Manning said. “It was just a noise issue.”

Twelve seconds in, the Broncos trailed and never recovered on their way to a humbling 43-8 blowout by the swarming Seahawks, a remarkable rout of the highest-scoring team in NFL history.

“That’s the way the start of any Super Bowl, it’s going to be loud,” said Wes Welker, now 0-3 in Super Bowls. “The fans are going to be yelling. They don’t really know why they’re yelling. It’s just the start of the Super Bowl. We didn’t prepare very well for that and it showed.”

Of all the mistakes and miscalculations that led to Denver’s dud of a Super Bowl, this one especially hurts because this team takes such pride in preparing for every little possibility.

At the Jets’ practice facility Wednesday, Fox had his team run several live drills with eight speakers on one side of the field blaring crowd noise to help with concentration, but he didn’t turn them on full blast.

“Normally, it’s about five times louder than that,” explained Fox, who had coached in the Super Bowl as the Giants’ defensive coordinator and the head coach of the Carolina Panthers. “It’s not an away game. The ones I’ve been to haven’t been too loud. So we just kind of practice with what we think we’re going to get.”

The Broncos’ self-inflicted mistakes were only just beginning.

Pressured relentlessly, Manning would lose a fumble and throw two interceptions, including one that game MVP Malcolm Smith returned for a 69-yard touchdown that made it 22-0 at halftime.

“This was our worst execution all year,” said tight end Julius Thomas, one of a record five Broncos who had scored double-digit touchdowns during a record-shattering 606-point season.

“We just never found a rhythm offensively,” added wide receiver Eric Decker. “We got behind and we had to cut down on what our game plan was and couldn’t do certain things.”

While Bruno Mars was crooning at halftime, the Broncos still believed they could make President Barack Obama look good when he predicted a close game in a pre-Super Bowl interview with Bill O’Reilly.

The Seahawks needed all of 12 seconds to score after the break, too.

Matt Prater, who led the league by a wide margin with 81 touchbacks on kickoffs, pooched the kickoff in an apparent attempt to keep it out of Percy Harvin’s hands.

Harvin, however, gathered it at the 13 and raced 87 yards for the score that made it 29-0.

The Broncos were effectively finished, although Manning would go on to complete a Super Bowl record 34 passes and Demaryius Thomas would catch a Super Bowl record 13 of them for 118 yards and a touchdown — Manning’s 100th in two years for Denver.

Manning’s other losses with the Broncos were by six, six, 10, three, six, three and seven points — 41 altogether — almost as much as in the Super Bowl.

“We worked hard to get to this point and overcame a lot of obstacles to get here, putting in a lot of hard work,” Manning said. “It is a really good thing just to have this opportunity, but certainly to finish this way is very disappointing.

“It is not an easy pill to swallow, but eventually you have to.”