Sen. Howard W. Cannon is a Nevada Democrat who does not think there is much to be gained by muffling existing two and three-engine jet planes as federal regulations require. Yesterday morning he marched his Senate aviation subcommittee into the Dulles Airport boondocks to make his case.

It is not clear whether he won or lost, but it is clear from a survey taken by the Federal Aviation Administration that most of those there could tell that a muffled, three-engine Boeing 727 was quieter than an unmuffled one.

That did not help Cannon's position.

It is also the senator's position that new-technology planes, such as the Airbus Industrie A-300, are quieter than any kind of 727 and therefore a better buy for an airline than a muffling kit.

The FAA survey found that a majority of those gathered with Cannon among the ticks and mosquitoes a mile from the end of a Dulles runway agreed that an A-300 was quieter.

Score one for Sen. Cannon.

The issue is not trivial. It involves the question of whether the federal government will provide a tax subsidy to the nation's airlines to help meet an environmental regulation - something the government has not done for other industries required to meet environmental regulations.

The regulation requires that airlines either muffle their existing too noisy jet planes by 1985 or replace them with newer, quieter models. About three-fourths of the domestic fleet violates the noise levels and the cost of meeting regulations is estimated variously at between $3 billion and $7.5 billion.

The Air Transport Association, the airline lobby, says it must have federal money to meet that deadline.

Two House committee - Ways and Means and Public Works and Transportation - have decided with the support of the Carter administration that the muffling regulation is a good one and that the airlines need help.

They have agree to proposals that would divert one fourth of the revenue from an existing 8 percent on passenger tickets and part of a freight tax to defray the costs.

Cannon's bill would extend the deadline for compliance from 1985 to 1990 and would dedicate that tax money to guaranteeing loans for the airlines so they could make equipment changes.

The Airport Operators Council, which represents airport managers, is adamantly opposed to any extension. Under law, the airport managers must pay damages when annoyed citizens win suits charging excessive noise from airplanes. Through last November, the operators say, they have paid $266 million to settle noise suits and buy land in noise-impacted areas. Pending suits and claims total $375.5 million, the council has said.

The stakes involve House and Senate byplay on one of Cannon's favorite causes, airline deregulation, which the Senate has passed. Rep. Harold T. Johnson (D-Calif.), chairman of the House Public Works committe, is sitting on the deregulation bill. He does not deny the suggestion that he is holding it hostage for Cannon's agreement on a noise bill.

Those are the reasons the crowd of about 75 people at Dulles yesterday included Cannon, JOhnson, Transportation Secretary Brock Adams, at least two assistant DOT secretaries, a number of key congressional staffers, a representative from the Environmental Protection Agency, lobbyists from every conceivable position on aviation questions, and assorted children.

Eastern Air Lines contributed an A-300 and Braniff and TWA both provided 727s. The crowd was not told which 727 had been muffled.

Cannon, Johnson and Adams stood in the middle of a clearing that had been mowed and sprayed for insects just the night before. Adams held a noise meter. Everyone looked intently. (Hand-held noise meters are notoriously inaccurate; carefully calibrated readings were being taken by other sensitive equipment.)

The planes flew over four times on a takeoff pattern, then four more times on a landing pattern.

"There's definitely a difference," said Adams, "particularly on landing."

"Frankly I can't measure any perceivable difference on a single event," said Cannon.

The official, preliminary FAA meter readings showed that, on takeoff, the muffled 727 averaged 9 of a decibel less noise than the unmuffled 727, but on landing the muffled jet averaged 6 decibels less noise - a level about half as noisy. The A-300 was quieter than either 727.

Furthermore, that's the way the people heard it. Forty-one of 56 said that one 727 was quieter than another on takeoff, and 38 of them picked the muffled plane as the quieter one. The results were similar on landing.

"I don't think people around airports will be able to tell the difference," said Cannon. "My advice would be not to build or buy near an approach to a runway."