The final draft of a flightseeing noise study commissioned by the city does not say whether Juneau flightseeing noise levels are usual, unusual or even tolerable. The study does indicate that flightseeing noise can get loud and, more important, can last a long time.
"The study reinforced my impressions that in areas of our community, we do have fairly constant flightseeing noise," said McKie Campbell, senior environmental manager for Michael Baker Jr. Inc. Baker was hired by the city to conduct last summer's noise study and relied on sound engineer Paul Dunholter of BridgeNet International, a California engineering firm, to conduct the field work.
"While no individual noise event caused by flightseeing is of an extremely loud nature, the sound is very constant throughout the daytime during the summer season," Campbell said.
"If we hadn't done this study, we'd continue to do this 'he said, she said' stuff," said Juneau Assembly and Planning and Policy Committee member Frankie Pillifant. "There's no big bang with this study, but it does quantify the fact that duration of the noise needs to be addressed."
The study documents and analyzes noise levels in the city caused by helicopter and fixed-wing flightseeing and offers noise mitigation options. The study is based on a noise measurement survey done in residential areas of Juneau between July 29 and Sept. 1, 2000.
Monitors were set up at 16 semi-permanent locations around the city. These collected continuous one-second noise levels during the entire time the monitor was at a given location. Monitors at 21 temporary sites measured sound for about eight hours during different time periods. Data also were collected inside four homes throughout the study area.
The survey includes data on aircraft events, ambient noise levels, collection of aircraft operational and local weather data, according to BridgeNet's Dunholter. The study also differentiates itself from others done in the Juneau area, namely those of the Federal Aviation Administration and the National Park Service.
"The FAA's criteria on noise are focused on airports and do not satisfactorily measure and describe the flightseeing situation in Juneau," Dunholter said.
Similarly, the National Park Service developed noise-measurement methodologies based on surveys of visitors in park settings.
Study results show the loudest events measured from flightseeing aircraft in Juneau were 87 decibels, with typical highest levels in the mid to high 70s. A decibel is a unit used to express differences in acoustical power. It is a logarithmic function, which means that an increase of 10 decibels - for example, from 55 to 65 - means double the sound intensity. A decrease of 10 decibels means half the intensity. Noise above 75 decibels represents a level "that is hard to speak above," Dunholter said.
With respect to duration, helicopter noise most often lasted from one to three minutes and floatplane noise events from 30 seconds to one minute. Near helicopter landing and takeoff points such as Bonnie Brae Subdivision and the airport, noise events lasted as long as five minutes, according to the study.
"There's a lot of data in this study," said City Manager Dave Palmer. "The trick will be to convert the data into a plan."
The study has helped catalogue flightseeing noise and aircraft data and will provide a basis for noise modeling in the future, Palmer said. "If we go that way, the next step is for the consultant to plug in what-if scenarios: virtual aircraft routes, virtual heliports, new aircraft."
The study presents "mitigation options" that could be used to reduce the impacts from flightseeing noise. These include the use of new, quieter aircraft technology; alternative flight paths; satellite heliports; seasonal monitoring; and a mediation process.
Much of this already has been presented by the assembly in the past, Pillifant said. "The satellite heliports are something the assembly has looked at - a delicate subject with a lot of nuance," she said.
Pillifant said she would continue to support the aircraft noise mediation effort.
"(Dunholter) is telling us what we already know," said Kim Metcalfe-Helmar, a tourism-impact activist and member of the Peace and Quiet Coalition - the movers behind last fall's failed flight-noise abatement initiative. "The one good thing he says in the study is: 'Don't shift the problem to another part of town.' "
Fernand Chandonnet can be reached at firstname.lastname@example.org.