Last July George Hessler, a self-employed sound consultant and engineer, rigged up a Hewlett Packard 85 computer to a sound meter and microphone outside his Cabin John home for some graphic proof of the noise caused by jets flying in and out of National Airport.

Almost every day his computer printout, which registered the average noise level outside at 10-second intervals, displayed a series of frenzied peaks as the planes thundered overhead on the only federally approved northbound flight path to and from the airport.

Last Monday morning, Hessler's printouts began to look quite different. The series of peaks began to subside, as did the noise. The testing of a new scatter plan for flights in and out of National had brought relative peace and quiet to Cabin John.

"We're getting about 80 percent less flights and a corresponding reduction in noise. And we're delighted," said Hessler.

For Hessler and many other residents of river communties such as Cabin John and Tantallon it has been a satisfying week, the first time in their view that aircraft noise has been fairly distributed throughout the Washington area since the jets began flying the river corridor in 1967.

On some days, up to 275 jets can pass over these riverfront communities, and their residents have had to get used to the continual noise.

"It's really thunderous," said Allen van Emmerick, a Justice Department lawyer who has lived in Cabin John for seven years. "There are nights in the summer you can't turn the TV or radio loud enough to hear. You can't read. It destroys your concentration. You can't have a conversation."

Yesterday morning, van Emmerik was still trying to get used to the changes caused by the new flight patterns.

"Boy, it's so different from what it was," van Emmerik said. "For the first time, I was able to sleep."

Not that there wasn't still some noise.

"You see it's real high now. That's that propeller airplane going over," said Hessler, pointing to a peak on the computer screen chart in his living room as a plane flew overhead.

Hessler has been collecting noise data almost daily between 7 and 8 a.m., the first hour of National Airport commerical flights. A timer turns on the computer at 6:45 a.m., however, "to get what it is like without any airplane noise," Hessler said.

The charts indicating peaks in noise levels when jets fly overhead will be used to show a "graphic difference" in sound levels when Hessler and the Cabin John Citizens Association evaluate the scatter plan test. During the first four days of the test last week when many northbound jets began veering over Arlington and Georgetown rather then Cabin John, Hessler's charts showed fewer overhead flights and a much-appreciated reduction in noise.

"We still get 20 percent of the flights, but 20 percent is better than 100 percent," Hessler said.

The new recipients of jet noise don't find the 90-day scatter plan test so enjoyable. By late Friday, the Federal Aviation Administration, which is conducting the test, reported that 1,612 people phoned in to protest the test while only 442 supported it.

Jeanine Flaherty, 40, of Glen Echo said the noise from overhead planes rattled her home's windows one afternoon last week, disrupting her efforts to write some letters.

"It's just hard to concentrate. They come rumbling through," said Flaherty.

Virginia Quigley of Georgetown said, "Every minute of the day, we've had planes come over. . . . Everybody I've talked to are just ready to pull their hair out."

"I really feel sorry for them," said van Emmerik, and he seemed to mean it.

But to long-suffering Cabin John residents, the new plan seems eminently fair and they hope it will become permanent.

"The question is," said Doug Shifflet as he paused a moment from raking mulch, "are we all looking for our own self-interest or will we look for something that's fair, even though it benefits me directly?"