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La Jolla Aircraft Noise Monitoring Study confirms an increase, cites reasons

The “La Jolla Noise Monitoring Study” — conducted to evaluate the changes and causes of residents’ perceived increase in aircraft noise over the past year — determined that La Jolla faces unique exposure to noise from the skies due to its topographical features, a low ambient score, and the double-whammy of San Diego International Airport planes flying overhead early in the morning and late at night, and military helicopters and planes from Montgomery Airport flying overhead during the day.

The results of the study were submitted to the San Diego Airport Noise Advisory Committee (ANAC) during its Oct. 18 meeting in Point Loma. ANAC did not vote on the report, but accepted it for the record and will use it for reference when considering future changes to flight paths.

The 44-page report, released Oct. 11, was presented to the board by Paul Dunholter of BridgeNet International, an airport engineering and consulting firm that conducted the study.

The firm’s task was to evaluate the effects of the Federal Aviation Administration (FAA)’s decision to move the arrival flight path into San Diego Airport south over La Jolla as part of the Metroplex program, which reportedly took place this spring. Through Metroplex, flight paths are adjusted to make airspace more efficient. The FAA reports the projected annual savings are: $7.8 million in fuel; 2.7 million gallons of fuel; and 23.3-thousand metric tons of carbon.

Rather than point to one noise source, Dunholter said there is a “combination effect” in play that is causing peoples’ perception of more air noise in La Jolla.

“Overall, the airport has increased operations, so there’s a growth in air traffic and 14 percent more jet operations than in 2014,” he told the board. “There are a lot of changes that make things a little bit louder. Those things can build up together and result in the feeling of an increase in noise. La Jolla is situated near a number of airports that generate different flights … In general, the noise levels from San Diego International Airport (SDIA) operations were of a lower magnitude than ones that are not (from the airport), however, these start early in the morning and continue late at night.”

The report elaborates: “The maximum noise levels from SDIA operations in La Jolla were typically in the low 50s dBA (A-weighted decibels, an expression of the relative loudness of sounds in air as perceived by the human ear), while the typical single event noise level from non-SDIA operations was in the high 50s to low 60s dBA. In comparison to other areas, locations under the flight path in Point Loma experience maximum noise levels in the 80s dBA.”

During the day, Dunholter said, planes operating out of the Montgomery-Gibbs Executive Airport in Serra Mesa (with a runway that points toward La Jolla Shores) and military helicopters, fly along the coast and over La Jolla.

The report continues: “Aircraft from other airports generally result in somewhat higher single-event noise levels, since these are often propeller or helicopter aircraft that fly lower to the ground, generating noise in the 60s dBA to low 70s dBA range. Aircraft from other airports also have a more varied flight pattern and day to day fluctuations in the number of operations.”

La Jolla is further impacted by aircraft noise due to its topography and proximity to the ocean.

“One of the things that is also unique about La Jolla is there’s a lower ambient, which means aircraft will be more audible at a greater distance than in other areas. There are times, because of that lower ambient, you will hear aircraft continuously. These planes don’t fly right over, they fly around somewhat, so you get a longer term duration,” Dunholter explained.

“La Jolla also has elevated terrain and the water (ocean) that is like a mirror, so it reflects, and sound travels further, leading to a greater propagation of noise. With late night aircraft operations, there’s a push for departures around 11:30 p.m., when four or six of them go out at about 2 minutes apart. Because of the low ambient, there isn’t any respite or time between events for those who experience the noise.”

He also approximated that sound can carry for 30 to 90 seconds during each event.

Matthew Price, La Jolla Town Council representative, says the study ‘vindicates’ La Jollans’ concerns over the recent increase and intensity of aircraft noise.
Matthew Price, La Jolla Town Council representative, says the study ‘vindicates’ La Jollans’ concerns over the recent increase and intensity of aircraft noise. Ashley Mackin

During the meeting’s public comment period, La Jolla Town Council Airplane Noise Task Force representative Matthew Price said: “I believe the ‘La Jolla Noise Study’ really vindicates the community. It confirms what La Jollans feel, that there is a systemic issue with planes flying (nearby), and the report notes that. It also confirms what you’ve been hearing these La Jollans say, that they’ve lived here for 20 years and it is a quiet, peaceful place. And that’s because the ambient is so low. When you go from an average of 30 decibels to close to 50 decibels, that’s huge.”

As to whether the Metroplex system is to blame — which many La Jollans have asserted given the parallel timing to increases in plane noise and Metroplex implementation in other areas of San Diego — Dunholter’s study suggests not. Metroplex rolled out in two phases: November 2016 for Point Loma departures, and March 2017 for La Jolla and Mission Beach departures. 

He said the study measured one site “pre-Metroplex” to determine a baseline near UC San Diego. After the Metroplex implementation that affected La Jolla in spring 2017, five sites were monitored for “post-Metroplex” readings. “We correlated noise events with radar data and looked at the volume and duration of sound,” he said. “We were not able to measure a difference in the volume itself at the pre- and post-site.” 

Although the report listed no course of action nor recommendations to decrease noise, Dunholter offered a glimmer of hope: “We are looking at future-generation planes just coming into the fleet that I think are going to get noise levels down below where they are at this point.”

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