Adapting noise measurement and modeling practices to meet legislative and policy mandates for National Park management.

Abstract

Historical community noise studies focused on exposures corresponding to maximum tolerable annoyance and potential health risks. These criteria should rarely be pertinent for National Parks, but applicable knowledge and tools were developed by these studies. A-weighted measurements integrate sound energy across the audible spectrum to account for properties of human hearing. To improve the utility of A-weighted measurements, NPS is investigating band-limited dB(A) measures to exclude natural environmental sounds that have no bearing on the effects of anthropogenic noise. Leq metrics were shown to be reasonable for integrating time histories to predict human responses to noise exposure. NPS utilizes measurements of audibility to parse this measure into the extent of noise-free conditions and the Leq value when noise is audible. This approach distinguishes situations with chronic exposure to modest levels of noise from very infrequent exposures to loud events. Several noise models have been developed to support community noise management. These are used in park settings to model the kinds of individual noise events that can occur (a type of vehicle on a specific route). Interactive noise mapping tools have been developed to compute aggregate exposure from collections of many such events under different planning scenarios.