Assessing Community Annoyance of Helicopter Noise (2017) / Chapter Skim
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From page 58... ...
58 For reasons previously described, helicopter noise exposure levels were estimated by both measurement and modeling at the Long Beach and Las Vegas sites, and by noise modeling alone in Washington, D.C. 5.1 Comparison of Measurement and Modeling Estimates of Exposure Levels at Long Beach and Las Vegas Survey Sites The Long Beach and Las Vegas survey areas were fully developed residential areas, with substantial background noise.
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Analyses of Noise Exposure Measurements and Interview Findings 59 measured DNL values. Locations of dispersed flight tracks and numbers of operations assigned to dispersed tracks in the modeling software were modeled to measured estimates of DNL values.
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60 Assessing Community Annoyance of Helicopter Noise y = 1.0598x + 3.2351 R² = 0.9209 50 60 70 80 90 100 110 50 60 70 80 90 100 CW ei gh te d SE L (d B) A-Weighted SEL (dB)
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From page 61... ...
Analyses of Noise Exposure Measurements and Interview Findings 61 interview contact attempts. The "non-sample" category includes disconnects, businesses and other non-residential telephone numbers, fax machines, modem lines, wrong addresses, changed numbers, and non-English speaking households.
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62 Assessing Community Annoyance of Helicopter Noise Figure 5-3. Approximate locations of Long Beach respondents (in green)
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Survey Responses Green-Survey Respondents Red-Highly Annoyed (Helicopter) 1 mi N © 2016 Google l Figure 5-5.
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64 Assessing Community Annoyance of Helicopter Noise Table 5-4. Questionnaire response percentages and frequencies.
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Analyses of Noise Exposure Measurements and Interview Findings 65 Duration of Residence (Item 1)
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66 Assessing Community Annoyance of Helicopter Noise rotors or interactions of the tail rotor with the main rotor wake)
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Analyses of Noise Exposure Measurements and Interview Findings 67 appreciable amounts of cumulative noise due to both helicopter and fixed-wing overflights. Figure 5-8 plots (a)
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68 Assessing Community Annoyance of Helicopter Noise Repeated-measures analysis of variance with varying covariates revealed significantly greater annoyance due to fixed-wing aircraft noise (after adjusting for fixed-wing DNL) than helicopter noise (after adjusting for helicopter DNL)
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Data Collection Site: Long Beach (a) Data Collection Site: Las Vegas (b)
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70 Assessing Community Annoyance of Helicopter Noise Data Collection Site: Washington, D.C (c) Figure 5-9.
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Analyses of Noise Exposure Measurements and Interview Findings 71 Hypothesis 2. The prevalence of annoyance due to rotary-wing noise is most appropriately predicted in units of A-weighted cumulative exposure.
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72 Assessing Community Annoyance of Helicopter Noise (a) 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 27.2-32.00 32.01-35.37 35.38-38.73 38.74-42.10 42.20-45.47 45.48-48.84 48.85-52.2 9 5 % C I P ro p o rt io n H ig h ly A n n o y e d b y V ib ra ti o n o r R a tt li n g Helicopter DNL Data Collection Site: Long Beach Proportion Lower limit Upper limit (b)
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Analyses of Noise Exposure Measurements and Interview Findings 73 (a)
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74 Assessing Community Annoyance of Helicopter Noise (a)
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Analyses of Noise Exposure Measurements and Interview Findings 75 Figure 5-14. Proportion (with 95% CIs)
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76 Assessing Community Annoyance of Helicopter Noise The logistic regression of buzzing noises on helicopter noise exposure was the only one that was unlikely to have arisen by chance alone, but even it accounted for very little variance in the relationship between annoyance and exposure. In the apparent absence of any strong association between helicopter noise exposure and annoyance at the low exposure levels that were available for study, it is likely that nonacoustic factors may have controlled community response to helicopter noise at the study sites.
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From page 77... ...
Analyses of Noise Exposure Measurements and Interview Findings 77 Reporting high annoyance with helicopter noise is predicted by reports of high annoyance by traffic and fixed-wing noise sources, and by whether respondents lived in Long Beach versus Washington, D.C. Respondents who were highly annoyed by fixed-wing aircraft noise were almost fifteen times more likely to be highly annoyed by helicopter noise than those who were not highly annoyed by fixed-wing aircraft noise.
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From page 78... ...
78 Assessing Community Annoyance of Helicopter Noise Helicopter noise exposure was greater for those who noticed helicopters (M = 43.27, SE = 0.192) than for those who did not notice helicopters (M = 41.73, SE = 0.191)
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From page 79... ...
Analyses of Noise Exposure Measurements and Interview Findings 79 5.5.1 DNL Versus Distance Relationships Figures 5-16 through 5-18 show DNL versus distance relationships for Long Beach, Las Vegas, and Washington D.C., respectively. They show orderly reductions in SELs with distance.
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80 Assessing Community Annoyance of Helicopter Noise Figure 5-17. INM-generated DNLs for each respondent at LAS as a function of respondent distance from flight corridor centerlines.
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Analyses of Noise Exposure Measurements and Interview Findings 81 Figure 5-19. Percent of respondents highly annoyed at the Washington, D.C., interview site as a function of A-weighted DNL for fixed-wing aircraft.
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82 Assessing Community Annoyance of Helicopter Noise Figure 5-21. Percent of respondents highly annoyed at the Washington, D.C., interview site as a function of A-weighted DNL for helicopters.
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Analyses of Noise Exposure Measurements and Interview Findings 83 Figure 5-23. Percent of respondents highly annoyed at the Washington, D.C., interview site as a function of distance from helicopter corridor.
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84 Assessing Community Annoyance of Helicopter Noise than at LGB. Figure 5-25 plots the prevalence of percent highly annoyed against (A-weighted)
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Analyses of Noise Exposure Measurements and Interview Findings 85 Figure 5-27 shows the percent highly annoyed as a function of the C-weighted DNL. The C-weighting includes low-frequency noise far more effectively than does the A-weighting.
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86 Assessing Community Annoyance of Helicopter Noise Figure 5-29 shows response as a function of reciprocal distance in the same manner as for Washington, D.C. Other than a singular point, there is no clear trend of increasing annoyance with decreasing distance to the helicopter corridor.
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From page 87... ...
Analyses of Noise Exposure Measurements and Interview Findings 87 Figure 5-31. LGB, percent highly annoyed as a function of A-weighted DNL for helicopters.
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88 Assessing Community Annoyance of Helicopter Noise Figure 5-33. LGB, percent highly annoyed as a function of distance from helicopter corridor.
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Analyses of Noise Exposure Measurements and Interview Findings 89 The Long Beach dosage-response curve shows an increasing level of annoyance with increasing A-weighted DNL. This was the only survey site of the three sites where this clear trend is shown.
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From page 90... ...
90 Assessing Community Annoyance of Helicopter Noise 5.6 Results of Low-Frequency Noise Analysis Low-frequency noise emissions of helicopters are of particular concern as identified in Chapter 1 of this report. Fixed-wing jet aircraft noise consists of broadband noise spread over the audio spectrum, but helicopter noise is characterized by distinct frequency characteristics.
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From page 91... ...
Analyses of Noise Exposure Measurements and Interview Findings 91 wind passing over the microphone grid. In general, and what was used for this study, a 4-inch windscreen made of open cell foam is used.
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From page 92... ...
92 Assessing Community Annoyance of Helicopter Noise impulse C scales. Also calculated and shown is the SEL for C-weighting using only the frequency data available in INM and AEDT, i.e., frequencies above 50 Hz inclusive.
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From page 93... ...
Analyses of Noise Exposure Measurements and Interview Findings 93 50 Hertz, and if the atmosphere relative humidity is 40% then the attenuation due to this atmosphere is 0.111 dB per km. For the same conditions but for 500 Hertz, the attenuation is 2.18 dB per km, and at 5,000 Hertz, the attenuation is 69.7 dB per km.
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94 Assessing Community Annoyance of Helicopter Noise during an entire event. LFSL is defined as a value at the time of a maximum.
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From page 95... ...
Analyses of Noise Exposure Measurements and Interview Findings 95 complaint data to the FAA, so the Long Beach data is a subset of the FAA database. The FAA database included 110 Long Beach complaints during the survey period.
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