More than 200 volunteers from 15 force areas attended the event on Saturday at Lancashire Constabulary’s headquarters in Hutton.
They competed against one another in a range of challenges and were treated to live music, a DJ and fireworks.
But residents from up to two miles away were disturbed by loud noise coming from the event until late at night.
Martin Fitzsimmons of Pendlebury Close, Longton, drove to the headquarters at 10.45pm to complain after struggling to get his grandchildren to sleep.
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He said: “It was going on all day and was so loud that at first I thought it was coming from the local pub or a neighbour.
“When I got to the headquarters a man just said they had permission from the council. But if I did that in my garden, I’d be shut down.
“It must have cost thousands and it sticks in your throat when the police have put their rates up.”
Other people on social media complained there had been no warning of the event, and that music and the PA system forced them to close windows.
Sergeant Helen Nellany, organiser of CadetFest, said the event was a success and warnings had been given.
She said: “Many of those in attendance were vulnerable young people from disadvantaged backgrounds – for some it was their summer holiday – and we are incredibly proud of their impeccable behaviour throughout the event.
“The celebrations also included a DJ, live music and fireworks on Saturday night, and although we went to great lengths to make residents aware that this would be occurring, we apologise to anybody who was disturbed by noise from the site.
“We had a production team in place who monitored the sound levels and any residents who arrived at HQ to find out what was happening were invited in to watch the closing event and the fireworks.”
British Transport Police will host the event elsewhere next year.