SAN FRANCISCO (KPIX-TV) — The howling gale forces winds, whipped up by a potent atmospheric river, whistled through the railing grates of the Golden Gate Bridge, creating an eerie sound track for the storm as it ripped through the San Francisco Bay Area.

The humming noise can be heard for miles and has been a source of annoyance for San Francisco residents ever since a handrail retrofit, designed to make the span more aerodynamic on gusty days, was put into place last year.

READ MORE: Eastbound Lanes Of I-70 Closed In Wheat Ridge For Rollover Crash

The slants are much narrower than the old handrails and vibrate in a strong wind.

“I couldn’t really describe the sound,” said Brianne Howell of San Francisco when she first heard the noise last year. “I think I described it as wind chimes at first and, then, like when you blow into a beer bottle. But then, like multiple beer bottles, because it’s different tones.”

Is it a hum? A ghostly wail? A Brian Eno-style soundtrack for the world’s most beautiful bridge? The noise is not easy to describe. Howell had been chasing the source since April. “What is that sound,” she remembers asking herself walking through the Presidio. “I’m kind of like: am I the only one hearing this?”

READ MORE: COVID In Colorado: Vaccines Available Before Every Event At Ball Arena In December

Paolo Cosulich-Schwartz with the Golden Gate Bridge District explained that the new railing makes the bridge more resilient to really high wind. “The slats on the new hand rail are much thinner than the old hand rail which means that air can flow more freely across the bridge,” Paolo Cosulich-Schwartz said.

The Golden Gate Bridge District says this was to be expected. During design, the district conducted wind tunnel tests on a scale model of the bridge under high winds.

On Sunday, Mother Nature gave the bridge its own wind test with near hurricane force winds. The National Weather Service issued a gale warning for the waters off the bridge.

MORE NEWS: 18-Year-Old Man Shot, Killed In Thornton

“Peak gusts have been around 70 mph on higher peaks with 40 to 50 mph gusts filtering into lower areas,” the weather service said. “Expect the winds to linger within the main rain band but cut back before the rain begins to let off.”