Assessing Community Annoyance of Helicopter Noise (2017)

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134 1. Fidell (2003) presents a broader tutorial on the findings, interpretations, and practical implications of com- munity noise research. 2. Note that these nonacoustic influences are more productively addressed at the community, rather than indi- vidual, level. As described in the paper on Community Tolerance Level, CTL, (Fidell et al. 2011) communities form unique attitudes about noise. Decades of efforts (e.g., Job 1988; Fields 1993) to quantify individual differences in sensitivity to aircraft noise have produced little information useful for prediction of annoy- ance prevalence rates, or for regulation of aviation noise. 3. The lowermost curve is FICON’s dosage-response relationship for the prevalence of annoyance for all forms of transportation noise. The Miedema and Vos (1998) curve is that of the European Noise Directive. 4. “Final Rule,” The New York North Shore Helicopter Route, 77 Fed. Reg., pp. 39,911–39,913. 5. FAA’s endorsement of A-weighted noise measurements for assessment of community noise impacts is in large part based on limitations of field-portable, analog-era sound level meters. Lacking the capacity for combining one-third octave band sound level measurements and identifying tonal signal components, it was not possible decades ago to directly measure PNL(T) values in the field. 6. Readers interested in additional detail about these frequency-weighting networks and noise metrics are referred to Mestre et al. (2011). 7. Idealized conditions include a stable and still atmosphere, close adherence to published flight paths and procedures, and ideal pilot technique. Because relatively few helicopter operations are likely to occur under all of these conditions, and because of the great sensitivity of helicopter noise emissions to minor changes in operating conditions, actual noise emissions in the vicinity of helipads may diverge considerably from predicted noise emissions. 8. Truncating the range of a predictor variable such as noise exposure level reduces the magnitude of any observable correlation with a predicted variable such as the prevalence of annoyance. 9. This is particularly true in areas orthogonal to runway centerlines, where the sideline noise exposure gra- dients for fixed-wing aircraft can be as steep as 10 dB per thousand feet. At airports with midfield helipads, this means that fixed-wing aircraft noise exposure levels are likely to decrease far more rapidly with distance from the runway than rotary-wing aircraft noise exposure levels. 10. Fidell et al. (2011) have suggested one potential solution to this problem—reliance on an assumed shape for the dosage-response relationship. 11. ISO Technical Specification 15666 (“Assessment of noise annoyance by means of social and socio-acoustic surveys”) does not recommend screening questions, but also notes that “. . . specific requirements and proto- cols of some social and socio-acoustic studies may not permit the use of some or all of the present specifica- tions. This Technical Specification in no way lessens the merit, value or validity of such research studies.” 12. Proprietary databases, constructed from multiple (e.g., credit bureau, census, telephone, etc.) sources, may nonetheless be useful for present purposes if they permit geocoding and sampling based on areas enclosed by vertices of polygons that can be defined by noise exposure modeling. 13. More recent methods of interviewing (e.g., smartphone- and Internet-based) are not as likely to yield population-representative samples of opinions, since they either permit respondents to self-select for par- ticipation in the survey and/or attract primarily respondents with prior interests in the subject matter of the interview. 14. Note that the width of the confidence interval varies not only with sample size, but also with the absolute value of the proportion estimated. The values shown in Figure 3.12 are based on a normal approximation to a binomial distribution, and should not be extrapolated beyond the plotted range. 15. INM 7.0d was released prior to AEDT 2b, but produces identical noise exposure predictions for identical inputs. Note that AEDT 2c was published after the technical work was completed for this study. Endnotes

Endnotes 135 16. In broad stokes, landline and wireless sampling frames are developed using a combination of public records and self-reported information. The starting point for compilation for the landline sampling frame is tele- phone white page directories. These directories are scanned, manually entered, and compared for accuracy. Public record sources, such as birth and mortgage records, are used to enrich this data wherever available. Enhanced-Wireless™ is based upon a self-reported sampling database of approximately 125,000,000 wire- less phones. Using Enhanced-Wireless™, samples can be targeted to specific demographic groups, including age, income, gender, presence of children, and ethnic groups—just to name a few. Enhanced-Wireless™ was developed by STS using a proprietary set of databases that includes product purchase data, warranty card information, survey data, and many similar sources of information. Enhanced-Wireless™ is not a panel. Its consumers are not opt-in, instead, it is very much like a landline listings sample—except for covering the wireless universe. 17. Site 4 is a special case. Noise levels measured at Sites 1, 2, and 3 were dominated by a police helicopter that circled and crisscrossed the area above those sites many times at low altitude at 1 AM. Site 4 (north of Sites 1, 2, and 3) was shielded from this operation by a converted garage about 15 feet from the micro- phone location. Site 4 recorded appreciably lower noise levels for this series of events than did the other sites. 18. The concern over revised flight tracks, known as the “Metroplex Project” was not anticipated at the time of site selection. While the project was known, the concern that it would generate was not known. The FAA had determined that no significant impact would take place. In hindsight, it is clear that Metroplex projects around the U.S. generated more concern than was anticipated. It is still unclear if the concern was in fact a noise issue or whether the mere announcement of the changes or some other nonacoustic effect generated the adverse response. In any event, Washington, D.C., was the only place where we had overlapping fixed- wing and helicopter operations in significant numbers. 19. The current version of INM, version 7.0d (FAA 2007), will be replaced by the Airport Environmental Design Tool (AEDT) Version 2b by the end of the current calendar year. Prior to INM Version 6, helicopter noise was modeled with the Helicopter Noise Model, HNM (Volpe 1994). The helicopter noise computation model from HNM was incorporated into INM beginning with INM Version 6. 20. This assertion assumes that compliance with ICAO standards for fixed-wing aircraft noise certification precludes vigorous adverse reaction in aircraft noise-exposed communities near airports. ICAO’s recom- mendations are consensus standards for noise levels that may not be exceeded by aircraft offered for sale in those member states who chose to adopt ICAO’s recommendations. ICAO’s noise certification standards are not intended to, and do not, in fact, preclude adverse community reaction to aircraft noise exposure. Indeed, it is commonplace for communities near airports served by large fleets of ICAO-compliant aircraft to oppose continued, unmitigated airport operation and expansion. 21. The influence of meaning on annoyance judgments was also demonstrated by Fidell et al. (2002b), who solicited annoyance judgments under highly controlled listening conditions to sounds with identical dura- tion and power spectra, but differing phase spectra. Large differences were documented between meaningful sounds and the same sounds with scrambled phase spectra. 22. For example, Ollerhead’s conclusions include no mention of the subjective impact of helicopter noise. 23. It is possible, for example, that rattle and vibration produced by fixed-wing aircraft at the relatively short ranges of the controlled helicopter flybys would also have created “excess” annoyance. 24. Descriptive statistical tools such as regression may also be used in some cases to estimate values of DNL that highly annoy half of the population at a given interview site. Such estimates do not offer all of the advan- tages of CTL analysis, however. The slopes of regression-derived estimates of DNL values that highly annoy half of survey respondents are not directly comparable in multiple communities, and levels of annoyance that annoy half of a sample of respondents often do not reach 50% at common levels of helicopter noise exposure.