Flight frequency at issue

A leading airport watchdog group says a recent report showing a small decrease in the noise level around John Wayne Airport ignores the fact that there have been more flights out of JWA.

“Residents who live under the arrival and departure paths are well aware of the increase in flights,” the AirFair group said in a statement. “It is not the 24-hour average decibels of the daily flights that residents notice.”

“There are 350 flights a day if you count the private jets, and that’s minimum,” AirFair board member Nancy Alston said, estimating an official increase that will be released by the airport sometime later this month. “I’d imagine we’re up 10 to 20 from last quarter’s report.”

JWA spokeswoman Jenny Wedge added that the airport is still committed to remaining within state sound regulations, adding they are the strictest in the United States. She downplayed Alston’s reference to flight increases, saying they “haven’t been significant.”

Private jets are often louder than commercial jets and can pose equally severe noise pollution to those surrounding the airport, Alston said.

Such jets are not regulated by a cap agreement the airport agreed to in 2003.

The group also took issue with the characterization offered by Wedge, who said the airport’s increase in 2007 could not be heard by the human ear.

Alston cited studies from the Universities of California and Wisconsin that make the case that decibel levels organize sounds logarithmically.

“Even a rise of 1 or 2 decibels can raise the volume of a sound from 28 to 60%,” she said.

Professor Fan-Gang Zeng, the director of UCI’s Hearing and Speech Laboratory, agreed that even incremental decibel increases could produce significant effects. The real-time boost in volume, he said, depends on the initial noise-level of the sound. For example, a small decibel increase from a refrigerator may be barely audible; but a sound like a jet plane increasing slightly may be quite noticeable.

“If you’re baseline is high — I assume the airline or airport noise is relatively high — that decibel difference may matter,” he said.

Zeng performed some calculations and came to the conclusion that the actual volume increase in the surrounding areas — depending on location — hovered about 0-4.23%. Most of the increases in sound are about one decibel.

“That would be discernible by the human ear,” he confirmed.

However, Vince Mestre, a noise consultant for the airport, said the sounds may be discernible only under certain circumstances.

“If you have a constant noise out of a speaker, and you rapidly varied that by one decibel, you’d be able to hear that,” he said. “But, if you made that change slowly over time — or, in the case of an airplane, you hear that noise, then it’s quiet, and you hear a new one — there’s no way you could discern it.”

CHRIS CAESAR may be reached at (714) 966-4626 or at chris.caesar@latimes.com.