The state noise control regulations for airports will become more restrictive at midnight Dec. 31, but neither Van Nuys nor Burbank airports will become any quieter as the new year begins.
A change in the regulations, however, appears to be setting up yet one more confrontation in the long-running battle between airport administrators and groups of anti-noise homeowners.
The noise protesters accuse airport executives of manipulating the rules to escape the intent of the state law and to avoid reducing the number of planes using their airports.
Airport administrators say they are doing the best they can, but airport noise is a difficult problem, involving factors from aircraft design to zoning to federal laws, which they cannot resolve by simply issuing commands.
The standard that goes into effect Jan. 1 "is not technologically feasible for a large airport with residences nearby," said Brett Lobner, the deputy Los Angeles city attorney who prepared Van Nuys Airport's request to be exempted from the new standard.
The quarrel will probably end up as the subject of a trial-like public hearing by the California Department of Transportation later this year, providing a new forum for the noise protesters.
"Absolutely, we're going to demand a hearing," said Don Schultz, president of Ban Airport Noise, a group formed to combat noise from Van Nuys and Burbank-Glendale-Pasadena airports.
Charged Richard Close, president of the Sherman Oaks Homeowners Assn.: "The airports have no intent of ever complying with the law." Close also represents an alliance of five homeowners groups from Studio City, North Hollywood, Van Nuys, Sun Valley and Burbank.
'Long Overdue to Start Complying'
"The airports are long overdue to start complying," said Gerald Silver, president of Homeowners of Encino, who for some time has been pointing to the coming change in state regulations in arguing with Van Nuys Airport authorities that they are expanding the airport's operations beyond legal limits.
Van Nuys ranks as the third busiest airport in the nation in the number of takeoffs and landings, which have been running at about 500,000 annually. It ranks as the busiest general aviation, or non-commercial, airport anywhere.
"The only acceptable option is a massive cutback in operations," Silver said, estimating it would take "about a 50% cut" to meet the new state standard.
Airport executives respond that they have already put many anti-noise measures into effect and that aircraft noise will be no greater after the rule change goes into effect, no matter what the change does to legal definitions.
At the heart of the dispute is a change involving the complicated, abstract method by which airport noise is measured under California law. The unit of measurement is the CNEL, or Community Noise Equivalent Level.
A CNEL is the daily average of decibel readings recorded by monitoring stations near airports, weighted by a mathematical formula designed to reflect the fact that noise is more annoying at night. Aircraft noise registered between 7 and 10 p.m. is multiplied three times before being figured into the average, and noises from flights between 10 p.m. and 7 a.m. are multiplied 10 times.
The results are used to draw imaginary lines around airports, a "noise footprint" marking the boundaries of the areas where the average CNEL reaches a common level. A 70 CNEL line defines the point where noise readings inside the line are higher than 70 CNEL, and those outside are lower.
The footprint is a statistical tool used to come to grips with aircraft noise, which fluctuates from moment to moment. In real life, the footprint has no fixed existence. A listener moving from one side of the boundary to the other would find it difficult to detect any difference in noise levels. The real footprint shrinks to nothing when no aircraft are landing or taking off, and balloons out to a far larger area when a fully loaded jet with a heavy-handed pilot is climbing rapidly away from the field.
In real life, the footprint shifts with the wind and the direction of aircraft traffic.
The daily CNEL averages are further processed into a quarterly average, which the Aeronautics Division of Caltrans uses to administer the state airport noise law.
The law sets a maximum average CNEL for residential areas and schools near airports. Industrial, commercial and agricultural areas, as well as the airport itself, are exempt. Airports are judged by the size of an area of "incompatible usage" they generate, meaning residential or school property where the average CNEL is above the state limit. The goal of the law is to eliminate all incompatible usage, either through reductions in noise or changes in land use.
Set at 80 decibels in 1975, the limit was reduced to 75 in 1976 and then to 70 in 1981. The level drops to 65 on Jan. 1, the final stage of the law.