More than 8,000 suburban Cook County properties are getting reductions in their assessed value because of jet noise from O’Hare Airport flight paths — with more such cutbacks in the offing for Chicago homeowners.

What some are calling the new “O’Hare discount” is bringing assessed valuation reductions of 4 to 5 percent to the owners of every single-family home and apartment building with no more than six units in Norwood Park Township, the Chicago Sun-Times has learned.

That amounts to 8,096 Cook County property owners, a record-setting number for reductions based on O’Hare jet noise because such an analysis has never been done before, according to officials with the office of Cook County Assessor Joseph Berrios.

More reductions will be rolled out in the months ahead for homeowners in parts of Maine, Leyden and Jefferson townships, which encompass Chicago. All such trims will be reflected in the second installment of 2016 property tax bills mailed in mid-2017.

Even with the latest reductions, homeowners in Norwood Park Township are still expected to see the property taxes based on their scaled-back assessments go up. That’s because the 2016 assessed value of the average home there increased by 16 to 20 percent before 4 to 5 percent was shaved off because of O’Hare jet noise, figures from the assessor’s office indicated.

“It’s a mixed bag,’’ said Arlene Jezierny, mayor of Harwood Heights, which is affected, along with portions of Norridge and south Park Ridge.

“Whether there’s an O’Hare discount, they [assessed valuations] still went up,’’ Jezierny said. “The main thing is, it is not lessening the O’Hare noise. It’s just giving people a 4 or 5 percent discount for the noise.”

This map shows Norwood Park and the southern part of Park Ridge that are within or near the O'Hare noise contour (green line and shaded area). The area shown is bordered on the south by Irving Park Road and Forest Preserve Boulevard, and on the west by Cumberland Avenue. O'Hare runways are on the left. | Cook County Assessor

This map shows Norwood Park Township, including the southern part of Park Ridge, and those areas within or near the O’Hare noise contour (green line and shaded area) receiving 2016 assessed valuation reductions. The area shown is bordered on the south by Irving Park Road and Forest Preserve Boulevard, and on the west by Cumberland Avenue. O’Hare runways are on the left. | Cook County Assessor

The assessor’s office based the reductions in part on the adverse effect it saw on the sale price of Norwood Park Township homes sold in the three years before O’Hare dramatically changed its flight paths in October 2013 versus the three years after, officials there said. Norwood Park Township homes either sold for less after the change, or for more — but not as much more as other homes.

“It certainly confirms what we have been saying all along — that aviation noise has had an impact on property values,” said Dan Dwyer of the Fair Allocation in Runways citizen coalition, which has been leading the charge against the new wave of O’Hare jet noise.

To produce its reductions, the Cook County assessor’s office conducted a two-year review of documented O’Hare jet noise complaints; 25 aircraft noise studies; home sale prices; “noise contours” of the areas due for the worst noise by 2021; and other O’Hare documents.

Tax revenue lost from reductions for some properties can be made up by increases on other properties. But assessor’s office spokesman Tom Shaer estimated that any effect on other homeowners would be “minuscule” given the massive amount of property taxes collected in Cook County. For taxes billed in 2015, that amounted to $13 billion, based on Cook County Clerk figures, Shaer said.

Letters were mailed on Sept. 13 and Sept. 14 to all 7,792 single-family homeowners and 304 multi-unit building owners in Norwood Park Township telling them that the assessor’s office was reducing their assessed value “due to increased aircraft noise from O’Hare International Airport” and “reconfigured flight paths.”

Those paths changed in October 2013 as part of an ongoing $8.7 billion airfield overhaul that has brought a barrage of arriving jets over Chicago and Norwood Park Township east of O’Hare and sent others out to the west, over Bensenville and Wood Dale. Jet noise complaints have soared ever since, catapulting past the half-million mark in July alone.

Norridge resident Brian Gaeor — who's also the village engineer — looks over a map with information on the impact of O'Hare Internationl Airport jet noise. The map was set up in the lobby of Norridge Village Hall. | Rosalind Rossi/Sun-Times

Norridge resident Brian Gaseor — who’s also the village engineer — looks over a map with information on the effect of O’Hare Internationl Airport jet noise. The map was set up in the lobby of Norridge Village Hall. | Rosalind Rossi/Sun-Times

Norridge resident Brian Gaseor, the Norridge village engineer, said that even with the O’Hare discount, his assessed valuation went up 12 percent. What that will translate into for taxes, only time will tell, he said.

“People don’t talk about assessments. They talk about taxes,’’ Gaseor said. “When the tax bill comes out, that’s when people start squawking.”

In Harwood Heights, residents have varying views on the O’Hare discount, Jezierny said.

“Some say, `It’s affecting our home value. Who will want to buy due to the airport?’ ” she said. “Others say, ‘What are you talking about? My assessment still went up.’ ”

Will the official declaration of an O’Hare effect by Berrios’ office create a stigma on such properties? State Rep. Robert Martwick, D-Chicago, didn’t think so. He represents parts of Norridge and Harwood Heights.

“The market is hot, despite the plane noise,’’ Martwick said. “Giving people a little relief on taxes, that only makes properties more marketable. I don’t think there will be a stigma associated with that.”

DuPage County homeowners west of O’Hare received property reassessments reflecting the effect of new flight paths last year, Addison Township Assessor Chris Kain said. About 2,000 homeowners saw their assessments drop 3 to 8 percent at that time, he said.