Assessing Community Annoyance of Helicopter Noise (2017) / Chapter Skim
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5 1.1 Introduction The literature review performed by the research team initially identifies prior design and analysis approaches used for research on community response to aircraft noise. Review of these prior design and anaylsis approaches then leads to a discussion of hypotheses that merit consideration in field studies.1 The review then identifies annoyance as the primary noise effect of concern and distinguishes between the direct annoyance of airborne noise and the indirect annoyance of secondary emissions (vibration and rattling sounds)
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6 Assessing Community Annoyance of Helicopter Noise operational flexibility of rotary-wing flight. High-speed impulsive (HSI)
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Literature Review 7 The solid black line, the community tolerance level (CTL) relationship, is the one recommended in the 2016 revision of International Standards Organization (ISO)
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8 Assessing Community Annoyance of Helicopter Noise rattle audibly. Such rattling noises can be annoying in their own right, whether or not accompanied by noticeable vibration, or by audible helicopter noise.
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Literature Review 9 1.3.4 Complaints In July of 2013, the Washington, D.C., Court of Appeals found that helicopter noise could adversely affect a residential population at an A-weighted cumulative noise level more than 20 dB lower than FAA's customary criterion of "significant" noise impact (Ldn = 65 dB)
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10 Assessing Community Annoyance of Helicopter Noise The tactic of assigning penalties treats the assumed excess of annoyance of helicopter noise as a simple problem of measurement, while ignoring the underlying causes of the supposed excess annoyance. Since the evidence supporting the assumption of excess annoyance is not definitive, the issue may not simply be one of physical measurement, however.
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Literature Review 11 accurately reproduce recorded or helicopter-like synthetic sounds under laboratory conditions while also preserving crest factor (ratio of peak value to average value of sound wave -- important with impulsive noise) , phase relationships (whether two sound waves are synchronized or shifted in time)
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12 Assessing Community Annoyance of Helicopter Noise Table 1-1 summarizes the laboratory (controlled listening) and field (social survey)
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Literature Review 13 • The flexibility of low-speed, rotary-wing flight lends itself to much more complex flight paths than those of fixed-wing aircraft. These complex flight paths cause the helicopter to accelerate/ decelerate along the flight path and can dramatically change blade vortex interaction (BVI)
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