Libreri and other airport-area residents say that the overnight noise of hub jets landing and taking off will disrupt their sleep, devalue their homes and, possibly, damage their health. Yet they worry that the federal government's system for rating jet noise is designed so that a federal environmental study now under way is likely to underestimate the disruptive effect the noise will have on them. Not so, says the Federal Aviation Administration, the agency in charge of an environmental review of the FedEx project expected to be completed in draft this fall. The FAA, other federal agencies and noise experts have devised a system that accurately measures how intrusive aircraft noise will be in areas surrounding airports, the FAA says. And administrators at FedEx and PTI promise to operate the hub so that noise is not a major problem for people living outside very limited areas, directly in FedEx's path.
Nobody disputes that under certain conditions, jet noise can be extremely unpleasant.
Jet noise is basically an engine problem. It's caused primarily by the combustion process inside a jet engine. Heated air makes most of the noise as it moves through the engine and into the cooler atmosphere, much the same way that thunder occurs in nature. Studies have shown that many people find jet noise more unnerving than other transportation sounds, such as highway traffic. Another study several years ago by the U.S. Air Force found that jet noise of 90 decibels would awaken 50 percent of the people sleeping within its earshot.