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3 This report provides airport operators and the surrounding communities with an improved under- standing of helicopter noise and provides a description of the current state of effective practices for managing helicopter noise impacts. In some areas of the country, helicopter noise has re-emerged as a topic of intense community concern. As can be seen in the literature, many of the helicopter noise research projects date back to the 1970s and 1980s, with more than half of the documents reviewed published before 1990 and an overwhelming number published before 2000. This Synthesis is one of three ACRP projects on helicopter noise that have been completed or are currently underway. The other two helicopter studies are ACRP S02-44, âGuidance for Helicopter Community Noise Prediction,â which has been published as ACRP Research Results Digest 24: Recommended Community Noise Model Enhancements to Improve Prediction of Helicopter Activity Impacts, and addresses the improved technical methods to model helicopter noise, and ACRP S02-48, âAssessing Community Annoyance of Helicopter Noise,â which was underway at the time this syn- thesis was produced in 2016. This project was undertaken to investigate acoustical and nonacoustical factors that influence community annoyance to helicopter noise, describing how this compares with community annoyance with fixed-wing aircraft and developing a research method to relate helicopter noise exposure to surveyed community annoyance. â¢ Chapter two begins with an overview of the unique characteristics of helicopters and helicopter noise and the roles of various stakeholders in helicopter noise management. â¢ Chapter three describes the community response to helicopter noise, including the direct annoy- ance associated with the airborne noise created by helicopters and the annoyance associated with so-called secondary emissions, which is the noise produced by rattling created by vibra- tion induced by helicopter noise as well as the response resulting from nonacoustic factors. This chapter also summarizes laboratory and field findings about helicopter-specific noise-induced annoyance and discusses the role of complaints in addressing helicopter noise. â¢ Chapter four presents a summary of the noise metrics used to describe helicopter noise. â¢ Chapter five is a summary of the literature review. â¢ Chapter six describes the purposive survey conducted for this report, which asked ten individu- als responsible for managing aspects of helicopter noise about effective practices. The airports and heliport were chosen based on the knowledge that they have a robust helicopter noise man- agement program and that the airport has a history of helicopter noise issues. â¢ Chapter seven identifies effective helicopter noise abatement and mitigation measures based on the findings of the survey and literature review. The report concludes with a set of references. Further technical discussion is provided in the appendices. â¢ Appendix A1 includes a short tutorial on the sources and nature of helicopter noise and an analysis of the correlations among noise metrics commonly used as predictors of community response. â¢ Appendix A2 presents a discussion of the differences in the various noise metrics that may be used to describe helicopter noise. â¢ Appendix A3 presents a description of a modern method of identifying the acoustic and non- acoustic effects on annoyance. chapter one INTRODUCTION
4 â¢ Appendix B is an annotated bibliography on relevant studies on the annoyance of helicopter noise and potential ways to reduce that negative impact in both laboratory and field settings. It is intended as an interpretive guide to the technical literature on the annoyance resulting from helicopter noise and its mitigation. The annotation focuses on the issue of the excess annoyance of rotary-wing aircraft noise. â¢ Appendix C is a copy of the Helicopter Association International (HAI) Fly Neighborly Guide. â¢ Appendix D lists the questions used in the airport survey. â¢ Appendix E provides examples of various airportsâ helicopter noise brochures. â¢ Appendix F is an example letter of agreement between the airport operator and the FAA air traffic control. Superscripts in the text refer to Endnotes that are located at the end of this document. Note: Within the aviation industry these aircraft are usually called rotary-wing aircraft or rotorcraft, but this report uses the more common term helicopter.