Local modeling

Growler noise study supports computer modeling

A $ 1.9 million study of aircraft noise at two Navy bases is unlikely to satisfy critics.

Last week, the Navy submitted its report to Congress on real-time audio monitoring of aircraft at naval air stations at Whidbey Island and Lemoore. The report says the Navy has determined that the noise models “are performing as intended and provide an accurate prediction of noise exposure levels from flight operations for use in impact assessments and long-term planning of the land use “.

In fact, the study reveals that noise modeling overestimates actual sound levels.

Noise abatement advocates, however, are skeptical of the study for its lack of independence as well as other perceived shortcomings.

“The Navy concludes that its real-time monitoring validates their modeling. Maybe, ”Bob Wilbur, chairman of the noise control group Citizens of Ebey’s Reserve, said in an email. “But they will have to be much more open.”

The Navy’s environmental impact study which was completed before the addition of 36 additional Growler EA-18G aircraft to NAS Whidbey and a fourfold increase in the practice Growler at Outlying Field Coupeville was based on computer modeling of aircraft noise. airplanes instead of real-world noise monitoring.

Professionals and hobbyists who measured the Growler’s noise near the OLF in Coupeville, including the Home Office, said the modeling significantly underestimated noise levels.

The Navy resisted monitoring until U.S. Representative Rick Larsen, a senior member of the House Armed Services Committee, added dual-base noise monitoring in the National Defense Authorization Act for fiscal 2020 .

“I am happy to see that the Real-Time Noise Monitoring Review has been completed, but I have asked the Navy to release the underlying technical data and expect to receive the data from the Navy soon. “Larsen said Wednesday. “I cannot draw any conclusions from the review without complete data.”

The report does not answer a central question the community has asked itself: how noisy is it in the houses surrounding the small Coupeville airfield?

Most of the report deals with “average day-night noise level,” a state metric and local officials questioned. It averages the sound over time and is used in civilian airline studies where the noise is lower but more continuous. Critics said this was not a fair assessment on Whidbey, where noise is much more sporadic; the result is that the sound peaks are diluted over time.

The report includes “noise exposure levels” for individual events at two locations on North Whidbey, but not around OLF Coupeville for some unclear reason. The report shows that computer models predicted single event noise at higher levels than actual measurements of single events.

The report states that further comparisons of noise exposure levels will be provided in a follow-up technical report.

The report shows that the “outliers” measured during the study “demonstrate the great variability observed in individual events due to various environmental and operational factors.”

For the study, the Navy collected real-time aircraft sound level and operational data during four discrete seven-day monitoring periods in 2020 and 2021. The sites were located around both the field base d’Ault and OLF Coupeville.

The data collected included acoustic recordings at sites around each airfield to capture sound levels during a range of flight operations in a range of seasonal weather conditions, the document said.

The study collected operational data, including logs from air traffic controllers and surveillance crews, to document expected and observed flight activity during each surveillance period, the report said.

“Although the results of this study indicate that the DoD-approved aircraft noise models are performing as intended, the Navy will continue to refine operational data collection procedures to improve the accuracy and reliability of the models,” the Navy concludes. report.