Since National Airport has been "de-federalized" residents living up and down the Potomac have been subjected to a nightly bombardment of jet racket from planes landing at the airport. No longer does the airport shut down at 10 p.m. -- the window-rattling noise now goes on well past midnight.

This nonstop racket just can't be good for anybody's mental or physical health. It means a relatively light sleeper such as myself can get no more than five hours of sleep at night. (I have to get up at 5:30 a.m. to go to work.) I have a well-insulated house with central air conditioning, but the jet noise comes through loud and clear. I have tried white noise and soothing tapes, but they are drowned out. Even wax earplugs are no match for the jets. Can you imagine what the racket level will be once we lose the leaf buffer this fall?

Since mid-June I have been trying, in vain, to find out who is responsible for the decision to unleash this ever-increasing nightly cacophony. Not the Council of Governments -- its spokesperson claims no COG authority, but it does have a working group studying the problem. (What a relief.)

A phone number listed in the telephone-book white pages under Washington National Airport Noise Complaints is a wrong number -- the number of some poor fellow who has no connection whatsoever to the airport. The information operator will give you a noise-complaint number one digit different from the phone-book listing, but a call to that number elicits a "Sorry, this is no longer a working number" response. The new airport authority will give you the names of two people who take noise complaints, but neither has ever been available to take any of my many calls.

Our duly elected representatives have no responsibility either. They are quick to take full credit for being the driving forces behind the magnificent achievement of "de-federalization," but they don't answer letters asking them to be the driving forces in the effort to stop the late-night airport racket. As near as I can tell, nobody is responsible for this noise pollution, and it's getting worse and worse. Isn't there anybody out there who can stop the racket?

DONALD R. MUELLER Arlington