But the 42-year-old U2 fan put up with his aching ears, even breaking into a toe-tapping "dad dance" when the world's biggest boy band belted out their big numbers.
"The amount of grief I'm taking from my mates for coming here is unbelievable. But I had to do it for the kids," he said, smiling at his twin 12-year-old daughters Alisha and Kendall who were enraptured by the show.
As much as he loves his daughters - and his wife Kyleen who was also enjoying the show - Mr Brook wished he'd bought earplugs.
The packed crowd, comprising largely of girls aged between 10 and 18, screeched in unbridled adulation as the English/Irish pop mega-group of Niall Horan, Zayn Malik, Liam Payne, Harry Styles and Louis Tomlinson kicked off their New Zealand tour.
It was near Beatle-mania for the Gen-Y2K crowd.
A decibel meter reading taken inside the arena peaked at 113.9 decibels (dB).
The average human pain threshold for noise is 110 dB. Anything louder than 85 dB can cause permanent hearing loss.
Mr Brook covered his ears to block out the screeching all around him.
"Where's the bar?" he joked.
While the Dunedin car dealer was suffering, those around him were enraptured by the experience.
"It's better than I could ever have imagined," said Lucy Milne, 14.
After an energetic opening set by 5SOS, the excitement and anticipation levels soared.
One young female fan said: "I'm so excited," to which her friend replied: "I'm so scared!"
Some fans were weeping with joy during the show.
Zayn appeared to be the biggest hit with the girls, the decibel meter soaring every time he had a solo.
The lads interacted plenty with their adoring audience, utilising the large catwalk stage.
No one remained in their seats, glow sticks lit the dark arena, and the screaming and singing along was ceaseless.
Noise levels:
* Sound waves become shock waves - 194 decibels (dB)
* Jet plane taking off - 120 dB
* Chainsaw (at 1m away) - 117 dB
* One Direction concert - 113.9 dB
* Average human pain threshold - 110 dB
* 1964 Beatles concert in Wellington - 109 dB
* Lawnmower - 106 dB
* Rugby crowds - 105 dB
* Vacuum cleaner - 70 dB
* Normal conversation - 60 dB
* Moderate rainfall - 50 dB