Improving AEDT Noise Modeling of Mixed Ground Surfaces (2017) / Chapter Skim
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Pages 61-102
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From page 61... ...
6-1 CHAPTER 6. FINDINGS AND APPLICATIONS The findings and applications presented below were accomplished in response to the stated goals of this project.
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From page 62... ...
6-2 6.1. Fresnel Zone Ellipse Resistivity versus 2D Profile Cut It is worth looking at the difference between calculating the average flow resistivity in the Fresnel ellipse versus only considering the average flow resistivity along the major axis of the ellipse.
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From page 63... ...
A average fl routine re equally-sp be colloca requested every foo Because t respect th two grid p kPa s/m2. percent o resistivity A profile cu 10 ft grid created fr the area it then the 1 of 100, 00 flow resis simple prof ow resistivit turns the int aced distanc ted at grid p ; thus, reques t; whereas, he profile cu e boundary t oints with fl For calcula f hard surfac even when th s a check o t, 3 different spacing, and om the NLCD represents.
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From page 64... ...
6-4 The values of the calculated average flow resistivities in the ellipse using the different grid resolutions are shown in Table 8. It can be seen that increasing the grid resolution before calculating the average flow resistivity along the profile cut for this ellipse does not significantly change the difference with the weighted area (exact)
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From page 65... ...
6-5 TABLE 8. Average Flow Resistivity Calculations with 4 ft High Receiver Method Grid Resolution (ft x ft)
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From page 66... ...
water-land dependen U example s by 1 ft. showed th area in the percent h resolution the averag interface is t, no further a sing the prof hown here pr The compari at there was Fresnel ellip ard result w .
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From page 67... ...
FIGURE 42. Difference of average flow resistivity calculations for 8 kHz.
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From page 68... ...
6.2. Stra A mentioned octave ban one-third of the jet Model Par Flow Resis Elevation A Distance (f *
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From page 69... ...
In propagatio Propagati two effect for the ran conditions These effe A line of deviation model ap AEDT.
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From page 70... ...
6-10 the models is limited. The former is also important in that small improvements in accuracy might be forgone if they require too large an effort.
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From page 71... ...
FF IGURE 45. groun IGURE 46.
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From page 72... ...
6-12 While there are more complex models to estimate ground impedance from a variety of parameters, the most commonly used approach for calculating ground impedance is the one-parameter model which requires an estimate of the ground flow resistivity. Because estimates of flow resistivity have been associated with the ground cover in the NLCD, the one-parameter model can be applied over large areas anywhere in the United States.
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From page 73... ...
A significan The softw based on than the o L 0.01 and deemed to parameter from wha values tha values and F statisticall weighted significan W angle bec again not W significan provide a n important ce test that in are John's M results gather bserved samp ow p-values lower (99% be statistic s were not an t was compu n the normal the model's igure 47 sho y significant ground atten t input param hen the com omes a highl significant in hen air atten t input param significant i output char dicates the i acintosh Pr ed from EGA le result (Tri indicate statis degree of co ally significa important p ted. Highly statistically resultant out ws the DOE and not stat uation values eters, wherea FIGURE puted ground y significant this scenario uation and sp eter and el nfluence ove acteristic for nfluence of i ogram (JMP)
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From page 74... ...
6-14 effects and spherical spreading, neither of which are functions of flow resistivity, dominate the source attenuation computation obscuring ground impedance effects.
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From page 75... ...
A single eve other leng difference Figure 51 model the noise rang segments highlighti operation using a gr similar to expected. receptor gri nt SEL (dBA ths indicated between the .
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From page 76... ...
T results pre the ends geometric formulatio increased threshold. he vehicle fl sented in Fi of the flight area of influ n in the AED fidelity, how FIGURE ight altitude gure 53 indic track, and a ence.
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From page 77... ...
FIGURE 50. altitude: a)
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From page 78... ...
FIGURE 51. ft alti Baseline SE tude.
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From page 79... ...
FIGURE 52 250 ft a . Baseline S ltitude.
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From page 81... ...
W Adjustme Ground A INM Tech long segm The relati combined ithin INM nt" which is ttenuation an nical Manua ent. The ne ve impact of effect.
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From page 82... ...
F6.5.4. App T AEDT: a A Attenuatio AEDT Ac Geometric and acous T uncertaint IGURE 56.
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From page 83... ...
6-23 increased. The NF uncertainty sets both the minimum uncertainty possible and the smallest required segment size while the ground effect physics and IMLS will potentially permit longer segments without increasing uncertainty.
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From page 84... ...
6-24 The study by Plotkin et al.
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From page 85... ...
6-25 supplement the new ground effects method(s) because AEDT currently includes engine installation directivity as part of the lateral attenuation.
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From page 86... ...
The following Events 107 is The tim were u slant d temper The N files w ellipse was fo the elli The E ground ellipse The at calcula sound airplan added distanc FIGU procedure wa where the w less than 70 d e of an aircr sed to find th istances to th ature) to find ational Land ith flow resi s for the cent und using the pses occupie GA model w effect.
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From page 87... ...
6-27 The A-weighted levels of the resulting spectra were calculated and corrected for the engine installation effect according to SAE AIR 5662. Figure 58 shows the result of these calculations for each event.
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From page 88... ...
FIGURE 58. Corrected Levels at PDX Monitors.
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From page 89... ...
F6.7.2. Da T Monitorin meteorolo provided history da airfield an S would be propagatio acting as measured the levels noise leve IGURE 59.
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From page 90... ...
l FIGURE 60 ines represen . A-weighted t arrival tim time histor es of sound point ies at GRU 3 emitted from of closest ap 5 and NMT B747-8 dep proach.
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From page 91... ...
6-31 The slant range at the point of closest approach to GRU35 for a departure from runway 28R is 387 ft. Similarly, the slant range to NMT11 is 11, 317 ft.
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From page 92... ...
6-32 As before, if the corrected level from the lateral monitor matches the one from the undertrack monitor, then the EGA model is accounting for lateral attenuation correctly. Figure 62 shows a comparison of the corrected levels with the mean and standard deviation of the difference levels.
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From page 93... ...
FIGURE 61. Elevation angles of operations satisf criteria at SF ying wind sp O
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From page 94... ...
FIGURE 62. a Compariso round SFO.
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From page 95... ...
FIGURE 63. Compa SFO rison of cor data set.
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From page 96... ...
6.7.3. Da T data, nois weighted history da Monitor T T propagatio monitors promising ta Validatio he ANOMS e monitor da time history ta (see below erminals (NM he focus of an n over mix were investi pair consist F n at OAK data obtained ta, and aircr data for the )
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From page 97... ...
6-37 noise monitor (NMT12)
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From page 98... ...
If the model F be seen in are higher be seen in Subtra distanc Apply runwa Calcul maxim the A-weigh ing of EGA f FIGURE igure 66 show the figure, th than those m the figure, t ct from the e from GRU ground effec y 30 and NM ate the A-w um level me ted level of th or the ground 65. Noise m s a compari ere is a distin easured.
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From page 99... ...
the groun corrected to it. The to the spe the correc probabilit distributio T the measu from the 0.0 dB w effect at g F T It may als the maxim would be measuring model co incidence d effect from for ground ef ground effe ctrum.
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From page 100... ...
14,000 kP monitor lo high flow a s/m2 for cation does resistivity. all Fresnel z appear to hav FIGUR one ellipses.
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From page 101... ...
FIGURE 68 airfield, air a . Comparis bsorption, a lin on of levels f nd spherica e with unity rom GRU36 l spreading w slope draw corrected o ith measur n for compa nly for grou ed levels at N rison.
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From page 102... ...
FIGU ground RE 69. Pro effect, atmo bability plot spheric abso Dash-dot of difference rption and ted line repr between GR spherical spr esents Gaus U36 levels eading and sian distribu only correct measured le tion.
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