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Abstract
Sound land use planning requires accurate predictions of the acoustic signatures at noise-sensitive receiver points and methods for interpreting the effect of acoustic signatures on public health, safety, and welfare. Historically, the study of noise impacts from aviation has been focused on fixed-wing aircraft, while the complexity of helicopter and new-technology rotary-wing aircraft has not been given adequate attention. This paper outlines recommended key community noise modeling elements required to accurately capture helicopter and tiltrotor noise which are suitable for inclusion in civilian regulatory integrated models such as the Aviation Environmental Design Tool (AEDT) [Koopmann et al., 2012, 2012a]. The National Academies of Science Airport Cooperative Research Project ACRP 02-44 has recognized that in contrast to guidance related to fixed-wing aircraft, there is no peer-reviewed guidance document describing an integrated modeling technique for the prediction of helicopter noise. This project was initiated in order to document current practice, improve modeling methods, and provide guidance for improving AEDT to predict helicopter and tiltrotor community sound via definition of a framework to compute aggregate annual average noise in concert with documented United States and international civilian community noise modeling needs. This paper does not attempt to identify which noise metric best predicts annoyance; it recommends a computational methodology from which suggested metrics may be accurately determined. This paper is also not intended to address military computational needs for mission survivability or probability of electronic or human aural detection. The AEDT framework was examined from a source – propagation – receiver perspective and recommendations are provided herein. The existing standards behind the Integrated Noise Model [Boeker et al., 2008; Dinges et al., 2007] and AEDT predictions [SAE, 1986; ICAO 2008; ECAC 2005] were examined, and where necessary, proposed enhancements to improve community noise modeling are provided. The author recognizes that there exist higher fidelity rotorcraft noise models and current research is continually advancing the state of the art. The user input burden and access to vehicle specific data, however, must be balanced with the general requirements of community noise modeling. The recommendations suggested here are in concert with today’s typical community noise modeling practices, level of effort and input data constraints are targeted specifically for AEDT. The framework for INM/AEDT modeling is well established for fixed wing aircraft. The historical integrated Heliport Noise Model [Fleming & Rickley, 1994] forms the basis of the INM/AEDT rotorcraft core. As with most noise models, these key elements must be included: Source noise characteristics (level, directivity, spectra/metrics, conventional/tiltrotors); Operational capabilities (takeoff, landing, hover in/out of ground effect, orbiting, tiltrotor modes); Propagation modeling (atmospheric models, natural and urban terrain, spectral domain, range); Community Noise Metrics (single and multiple operation contours, standard and supplemental metrics). An outreach task was conducted in order to solicit feedback from the international rotorcraft noise modeling community on the recommended technical modeling approach details and changes for AEDT/INM. The intent was to provide an efficient mechanism for distribution of the modeling rationale and to solicit international rotorcraft noise community stakeholder feedback in response. The recommendations are intended to help guide development of a draft helicopter and tiltrotor noise standards document under the auspices of the SAE Aerospace Technical Committee A-21, Aviation Noise and Emissions Committee. International outreach consisted of an online Webinar facilitated by the National Academies of Science, presentations at technical meetings at helicopter symposia, noise and emissions and transportation related committee meetings and events and distribution of an explanatory white paper via email. This paper outlines the final seven specific recommended helicopter and tiltrotor modeling elements for AEDT and presents the rationale behind each.

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