The FAA concludes that the proposed changes will not increase noise much.
FAA Order 1050 stipulates that increases of 1.5 dB or more in areas already exposed to noise > 65 dB, increases of >3 dB in areas already exposed to 60 – 65 dB or increases >5 dB in areas already exposed to noise 45 – 60 dB “could be disturbing to people and become a source of public concern”. To study the proposed changes in approach and take off routes, they did noise modeling and concluded that none of the changes would increase noise levels beyond this threshold. The WHO threshold for noise toxicity is 55 dBA.
|DNL Noise Exposure Level||Increase of DNL requiring action||Aircraft Noise Exposure Change Consideration|
|DNL 65 and higher||DNL 1.5 dB and higher||Exceeds threshold of significance|
|DNL 60 - 65||DNL 3.0 dB or more||Reportable Noise Increase (Considered when evaluating air traffic actions|
|DNL 45 - 60||DNL 5.0 dB or more||Reportable Noise Increase (Informatiion disclosed when evaluating air traffic actions.|
This is a report of an extensive study on how more efficiently to make use of the airspace in the Bay Area. It concentrates largely on fuel efficiency and simplifying communication with ground. Effects on the community do not appear to be an issue in this study.
This is an excellent paper on the derivation of DNL (Day-Night Sound Level) as a noise metric. They note that “Nearly all agencies and boards, standards setting bodies, and international organizations that have cognizance over noise producing sources use a DNL criterion value of 55 dB as the threshold for defining noise impact in urban residential areas. In fact, of this large number of agencies, boards, standards setting bodies, and international organizations, only the
Department of Defense and the Federal Aviation Administration suggest a criterion value for
DNL that is higher than 55 dB.”
They go on to state: “Of all of the boards and agencies, standards setting bodies, and internationals organizations, one should consider the World Health Organization and the National Research Council as the primary authorities on acceptable levels of pollutants. They are charged with developing this type of scientific position and have clearly spoken. WHO terms DNL 55 dB as engendering serious annoyance and creating an unhealthy environment, and WHO terms DNL 50 dB as engendering moderate annoyance.” (Italics added)
An interesting read.