The bitter dispute between Butter Cream Bakery and a neighbor made desperate by night noise is taking a new turn.

After years of siding with the bakery, the city of Napa is going to make Butter Cream Bakery prove that it isn’t violating a city noise permit.

If Butter Cream is violating the law, “we will enter into way more aggressive enforcement,” City Manager Mike Parness told the City Council Tuesday night.

If necessary, the city will go to court to make sure that the bakery follows the city’s noise limits, Parness said.

Rick Esser, who lives behind the Jefferson Street bakery, has been waging a one-man campaign for four years to get the city to crack down on Butter Cream.

Esser, a piano teacher, has repeatedly appeared before the council, saying that ventilators over donut fryers and a refrigerator compressor had made his life a “living hell.”

Unable to sleep at home, Esser has resorted to sleeping in his car, at Skyline Park and at his wife’s gymnastics studio.

Butter Cream managers have said the operation is in compliance with local noise limits.  Former Napa City Manager Pat Thompson issued Butter Cream a noise permit five years ago, finding that the bakery’s mechanical equipment did not create unreasonable noise.

In 2003, the council upheld Thompson’s decision. Several council members said they had visited Esser’s neighborhood at night and had not heard excessive noise.

Esser, who lives on Spencer Street, continued to come to council meetings once or twice a month to ask for a rehearing. The night noise from Butter Cream was ruining his life, he said.

Councilwoman Juliana Inman, elected to the council in November, reopened the case in December at her first council meeting. Staff needs to take a fresh look, said Inman, whose children were once taught piano by Esser.

Delving into the city’s files, Inman said Wednesday that she had found old acoustic reports that suggested the bakery was making too much noise at night.

Surprisingly, the “biggest culprit” weren’t the rooftop vents, which have bothered Esser the most, but a refrigerator compressor farther from his home, just a few feet from I Street, Inman said.

Butter Cream’s noise permit “lacks clarity,” Inman said. The city restricts the bakery to no more than 60 decibels at night at its property lines, but calculates noise as a 24-hour average.

The compressor on I Street is “putting out about 85 decibels at the property line,” she said.

Inman said she has made solo visits to Esser’s property several times in the middle of the night — and once at 9 p.m. with Assistant City Manager Dana Smith, Steve Jensen, the chief building official, and technicians from Bell Products, the bakery’s contractor.

Various mechanical components were turned off and on. The compressor on I Street produced by far the loudest noise, followed by an air curtain over a rear entry, Inman said.

“I think a lot of people have been very subjective in their approach to this,” Inman said. “The data is what it is.”

Parness, who became city manager in November, said he had tried “shuttle diplomacy” between Esser and Gerry Closs, the owner of Butter Cream, but had achieved nothing.

“I’d been hoping to negotiate a fix that everybody could live with at very modest cost,” Inman said. “When people take intractable positions, that’s hard to do.”

Neither Esser nor Closs could be reached Wednesday despite several calls to their homes and businesses.

In a 2005 Register article, Closs maintained that the bakery was living within its permits. Although the bakery installed new roof ventilation in 2002, the equipment was far quieter than the old motors, he said.

Closs complained that Esser, who is married to Closs’ first cousin and was his child’s piano teacher, was hearing noises that would bother no one else.

Councilman Jim Krider visited the bakery at night in 2005 armed with a decibel meter. He reported measuring 79 decibels — the equivalent of a power lawnmower — from the sidewalk next to the refrigeration condenser.

Contacted Wednesday, Krider said he supported having professionals determine if the bakery is in violation.

Mayor Jill Techel said a new City Council, a new city manager and new department heads had made new judgment about Butter Cream. That’s the benefit of taking a fresh look, she said.

Even if Butter Cream lowers its noise, Inman said Esser might not be satisfied. “I don’t know if reducing the sound to what is permitted will make much difference to his peace of mind, but it’s the right thing to do,” she said.