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40 Figure A16 compares several dosage-response relationships between cumulative aircraft noise exposure and the prevalence of aircraft noise-induced annoyance in average communities. The solid black Commu- nity Tolerance Level (CTL) relationship is the one recommended by the Final Draft International Standard of the revised ISO Standard 1996-1. (The lowermost curve is FICONâs 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.) If helicopter noise is more annoying, decibel-for-decibel, than fixed-wing aircraft noise, the CTL curve in Figure A16 (developed for fixed-wing aircraft) will be shifted toward the left side of the graph. Figure A17 illustrates a family of dosage-response relationships corresponding to increases in the annoyance of helicopter noise exposure by amounts ranging from 3 to 10 dB. For example, if helicopter noise proves to be 3 dB more annoying than fixed-wing aircraft noise analyses of survey data may be expected to produce a dosage-response relationship similar to the dashed curve to the left of the one seen in Figure A16. Note that the curves in Figure A17 differ both in positions on the abscissa, and in their slopes, for reasons discussed in Appendix C. The shapes of the curves are identical no matter where they lie horizontally. However, the horizontal position affects the slope of a given curve at a particular dose (i.e., day-night average noise level value), and hence the rate at which annoyance grows with increasing dose at that level. APPENDIX A3 Community Tolerance Level, Accounting for Nonacoustic Effects on Annoyance FIGURE A16 Comparison of revised ISO Standard 1996-1 dosage-response curve with earlier curves derived by regression analyses.
41 FIGURE A17 Family of dosage-response curves for differing levels of community sensitivity.
