Airport Noise: Tolerance Is in Ear of Beholder

The roar from a Boeing 747 lumbering above Aliso Viejo on its way to land at El Toro Marine base spiked a noise monitor last month at Oak Grove Elementary School to register levels as loud as a coffee grinder.

For many residents of South Orange County, the noise from commercial jets using the base during two days of demonstration flights obliterated months of assurances by county officials that the skies would remain quiet if an international airport were built at the base.

The planes rumbling over houses and yards generated noise levels shared by blenders and power saws.

County officials are expected to release a report today on noise data gathered during the test flights. Similar reports already have been issued by the cities of Irvine and Laguna Woods, which conducted their own monitoring during the tests.

Despite jet noise that some residents branded unbearable, county officials insist that nothing changed their prediction that no homes or schools will fall within the airport’s high-noise zone as defined by law.

Is it possible for commercial jets to roar overhead every few minutes and still have the neighborhood considered quiet by government standards?

Under state and federal noise law, it is.

The disconnect lies in how noise is calculated for the purposes of regulating land uses around airports. Jets flying overhead may stop patio conversation and infuriate residents, but the law simply doesn’t recognize a single noise event as significant.

State and federal standards instead set noise levels based on sound generated over 24 hours, which averages everything from the shrill whine of airplane engines to the dead quiet of night.

The logic is perplexing to anti-airport activists who chafe every time a county official boasts of the “quiet” airport being planned at El Toro. County officials envision the airport serving as many as 28.8 million passengers a year by 2020. Flights would take off or land on average every four minutes, including at night.

“Loud noise events are what startle and disturb people, not something averaged into background noise,” said Leonard Kranser, who operates an anti-El Toro airport Web site. “People have been to LAX or John Wayne Airport, and they know what planes sound like.”

Consider John Wayne Airport. The area in which jets are as loud as 85 decibels on takeoff (the same as a blender) stretches from the airport all the way to the coast. But only a small slice of that area--550 homes in Santa Ana Heights--falls within an averaged noise zone of 65 decibels, in which land uses are restricted by law.

County planners predict that Laguna Woods would sustain the greatest average noise from a new El Toro airport, with an estimated noise average of 64 decibels. Aliso Viejo would be at 62 decibels.

During the demonstration flights in June, jet noise in Laguna Woods topped out at 101 decibels at a noise monitor set up near the golf course by city officials. A newspaper press makes about 97 decibels.

Physiologically, damage to hearing doesn’t occur unless there is continual exposure in the 90- to 115-decibel range, according to California occupational safety guidelines.

The Federal Interagency Committee on Noise agrees, stating that there is “no definitive evidence of nonauditory health effects from aircraft noise” particularly in areas with averaged noise below 70 decibels.

Tolerance Quantified

Politically, the issue is more about how annoying loud noises can be.

In 1978, scientist Theodore Schultz decided to quantify the relationship between noise and annoyance. Schultz used surveys to plot a curve that tracked the percentage of a population bothered by noise as the decibel level increased. It showed that annoyance grew gradually, to about 12% of the population at 65 decibels.

Above that, the percentage of those annoyed mushroomed with each boost in noise, which doubles with every 10-decibel increase.

But even at extremely low noise levels of about 40 decibels--ambient noise with occasional bird calls--Schultz found that 3% of the population still described themselves as “highly annoyed” by what they heard.

Both the state and federal governments based their noise standards on the Schultz curve. They set 65 decibels of averaged noise as the level above which land uses should be restricted, said John Leyerle, head of the noise abatement office at John Wayne Airport, which has the most restrictive noise regulations of any U.S. airport.

“[The level] is not a perfect measure of everyone’s response to noise, but it’s the best metric available,” Leyerle said.

The 65-decibel zone, called the Community Noise Equivalent Level, considers not only how loud the noise is but the duration and when it occurs. Because people are more sensitive to noise at night, the calculation adds 5 decibels to noise between 7 p.m. and 10 p.m. and 10 decibels to noise between 10 p.m. and 7 a.m.

Within the zone, new homes or schools cannot be built and existing buildings can be insulated at government expense if property owners promise not to sue over future noise.

“Experience has shown that cumulative noise is the best way to measure impact on people,” said Ellen Call, spokeswoman for the county’s El Toro project. “Every state in the union, plus the federal government, uses a cumulative [standard] to measure noise.”

She said El Toro is well-suited for an airport because 18,000 acres of vacant land will be around the runways.

“Some people will be annoyed no matter how loud or quiet it is,” Call said.

Residents Angry

Many South County residents are outraged by the averaged-noise argument and don’t believe that a jet making 100 decibels of noise can be averaged into insignificance.

“I certainly don’t find that believable,” said Betty Olson of Coto de Caza. “If you’re going to have one 85-decibel [event] in a day, that’s tolerable. But if it’s going to be 20, that’s not tolerable. It’s such a denigration of lifestyle, it boggles the mind.”

It also won’t be averaged noise that wakes up the household when a plane lands at 3 a.m., South County airport foes argue.

True enough, Leyerle said. But whether the household wakes up or sleeps through the night changes from house to house. A study of sleep disturbance around London’s Heathrow and Gatwick airports showed that, of all the incidents in which people were disturbed during sleep, fewer than 10% could be attributed to aircraft noise.

Kranser said he and other airport opponents are most annoyed by county officials who use the average noise level as proof that the new airport will be quiet and that no homes or schools will feel the impact in bothersome ways. He acknowledged that averaged noise is the only one that matters legally but said government has a greater obligation to protect the public.

“I think they’ve been hiding behind the legalese to mischaracterize the impact of the noise,” he said.

South County residents were heartened in June when pro-airport county Supervisor Charles V. Smith acknowledged that commercial jets affected households in Aliso Viejo and Laguna Woods during the demonstration flights. He said the county should consider providing insulation to homes outside the 65-decibel zone as a way of mitigating the airport’s impact.

If the airport is built, the government should provide insulation for areas with averaged noise as low as 50 or 55 decibels, Kranser said. But he’s not holding his breath, particularly since the federal government reimburses noise-mitigation programs only within the 65-decibel zone.

Kranser finds it unlikely the county would agree that people are affected by the loud but intermittent noise. “To do so,” he said, “they have to acknowledge that they’re devastating our quality of life.”