The dominant noise was the 2,000 high up in the Leppings Lane End, the sell-out crowd around them subdued and even starting to grow a little restless.
It told you everything about where the belief was in that moment.
The first half had been nervy for Sunderland. True enough they had not given many clear chances away but after a bright start they were understandably being pushed a little deeper, forced to go long early and inviting some pressure as a result.
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Half time was a chance to breathe, reset, and in the period after they were nothing short of outstanding.
Jack Clarke went close from the edge of the box, Patrick Roberts was denied only by a superb last-ditch block and then a good Bailey Peacock-Farrell save.
The Black Cats were winning their aerial duels, allowing them to get up the pitch and control the contest.
And then along came Barry Bannan.
This was always going to be the thing about these games, two evenly-matched sides packed with players of Championship quality. No side could expect it all their own way.
In the first leg Sunderland had nullified Bannan, who essentially ended up a bystander as the game played out far behind him.
Here Darren Moore unsurprisingly brought in Josh Windass after his impressive cameo at the Stadium of Light, and the two were able to rotate well. Bannan drifted and drifted, passed and passed, waited and waited. It was merely the slightest second that Sunderland switched off but when they did, the Scot was there in that left-hand channel to punish them.
Time stood still, a split-second that felt like an eternity as it dawned on you. Sunderland had been sliced up and the game was up. A good cross to the front post, a good finish from Lee Gregory.Hillsborough erupted and for a while, the stands quite literally shook. The home fans bounced, they lit up their phones, they sang their old songs.
It looked a long old road back.
When Alex Neil was asked about an intimidating atmosphere on Sunday morning, he gave a wry grin and dead-panned, 'what, people shouting boo?' But more notable was what followed. He did recognise the relevance of the question, that in key moments that noise and passion can mean home players get the ball a second quicker, snap into the tackle that little bit harder. This is what it felt like and extra time looked a distant hope, never mind a win.
That's even before we get to the emotional baggage that those who follow this club carry, the years of play-off pain feeding that sense that when something goes wrong, something else will follow. Brace yourself for it, this proud old club hurts again, when will this sleeping giant rise, etc etc.
It was in these moments, though, that a moment of Sunderland history was born.
Neil threw his arm out in despair but quickly regained his composure. He whistled for Danny Batth's attention, the centre back again imposing here but just beaten to that cross by Gregory.
He motioned for calm, to settle until they felt they were off the ropes. Batth nodded and rather than throwing bodies straight forward, Sunderland rode the wave and took it deep.
Neil opted against making a change. It was a bold call, because the running from the front four had been relentless and there were times when it was showing, particularly after such a quick turnaround from the first leg.
It had been the first time he had named an unchanged team since taking charge, his logic being that Sunderland couldn't afford just to sit in for 90 minutes.
"I had so much belief in that team and what they were doing, we didn't deserve to be trailing," he said afterwards.
It left Sunderland with an advantage in two key areas.
Minutes before the equaliser, Moore was forced into a defensive change after Sam Hutchinson suffered a concussion. He also made a key gamble, throwing on the forward-thinking Nathaniel Mendez-Laing at wing-back.
Clarke had been excellent from minute one, digging in to protect Dennis Cirkin as Wednesday targeted that flank. From deep he time and time again brought the ball out from the back, winning free kicks, relieving pressure.
When ten minutes of added time was announced, he looked just about out on his feet.
So when Batth picks up possession in his own half, there doesn't seem to be a great deal of danger. Somehow, Clarke finds another gear. Mendez-Laing steps in and switches off, and from nowhere an intake of breath. Is this on?
Clarke looks up, shuffles into the box. Just when you expect him to cut inside and drive across goal, he goes to the byline and drives it low with his left.
Liam Palmer, brought on to replace Hutchinson after impressing at wing back on Friday night, has been given a difficult brief in a game of this intensity and tension. Roberts is alive to his team-mate's plan and bursts into the six-yard box.
He has flickered throughout the two legs, pushing Wednesday back without quite getting that real, clear chance. This is his moment, and from here there is no way he is missing. Peacock-Farrell is beaten and for a moment a silence descends.
Wait, what? This isn't what Sunderland do. This isn't us. This never happens to us.
Is someone offside? This can't be real, can it? No, this is really happening. A wall of noise cascades from up high and in it there is surprise, relief, sheer joy. Then there are limbs flailing everywhere, people falling over seats and dancing in the gangways.
Neil's poise has been his greatest virtue in the eye of all Sunderland's storms but even he gives into this moment. He leaps into the night and roars, and then it is quickly back to business.
Jay Matete and Nathan Broadhead on, for energy and an outlet to relieve pressure. Callum Doyle on for another body in the box.
Nine minutes that seem to drag on to ninety but Sunderland hold on and they do so with relative ease, winning their headers as they did for the bulk of these two legs.
There has been little in but they are worthy winners.
They have dug in and they have shown their resilience, and yet again they have gone right to the end. Under Neil they have started to rewrite the definition of 'typical Sunderland'.
Bailey Wright conducts his post-match interview with blood dripping from his face and one-by-one, they queue up to echo a clear message: This is a special moment but the main job is still to be done.
And no one should under-estimate the challenge that lies ahead.
Just a night earlier Wycombe Wanderers had dug in with all their trademark resilience, knocking out an MK Dons side who have played some of the best football in the division this season.
Before long thoughts of that game will be all-consuming but not just yet.
First, a moment to take a breath and say, yes, that really did just happen.