A Sydney man has been beaten up and left for dead in a park near his home after telling a group of partiers to turn the music down.

The 47-year-old is stable in hospital after being found by neighbours but the incident has rattled the community who fear the worse is yet to come.

Late last night a 47-year-old who lives in a unit next to James Meehan reserve in Dee Why on the Northern Beaches called out to a group partying in the park, asking them to turn the music down.

A Sydney man has been beaten up and left for dead in a park near his home – after telling a group of partiers to turn the music down. (9News)

One witness said they “had a boom box” which was “really, really loud at one stage.”

Another said the man had been shouting from his balcony.

He went down to ask again but police say he was surrounded and bashed, ending up in hospital with facial injuries.

“He believes he was lying there for an hour but we’re to investigate that properly,” Inspector Vanessa Robinson from NSW Police said.

Councillor Vincent De Luca hopes the perpetrators are found quickly. (9News)

Councillor Vincent De Luca hopes the perpetrators are found quickly.

“NSW Police need to get onto this pretty quick, our community expect arrests and expect justice,” he said.

“Locals are petrified to even take their dogs for a walk.

“We have an epidemic of gang crime and that must be addressed.”

Incidents where a group target an individual is not uncommon on the Northern Beaches. (9News)

Incidents where a group target an individual is not uncommon on the Northern Beaches.

Some locals spoken to by 9News said they were scared, but Inspector Robinson maintained it was safe to go to parks.