Appendix C—PEI Computations

A A A

Index 1 2 3 4 5 6 7 References App A App B App C

C. 1 Detailed computations for the ‘Worked Example’

Section 5.4 of the paper contains a worked example of a PEI/AIE analysis of different operating configurations at Sydney Airport. The base computations for this example are contained in Tables C.1 and C.2. Table C.1 shows the number of persons within five N70 bands for the three operating configurations and then shows the computation of the partial PEI (and the AIE used) in each of the bands. Table C.2 cumulates the information in Table C.1.

The analysis in Table C.2 is particularly useful for examining the distribution of the noise load. For example, the table shows that in the ‘noise sharing’ scenario very little of the total noise load is in areas where the N70 exceeds 100 events per day. For the noise sharing scenario this figure is about 12% of the total PEI, by way of comparison in the parallels scenario the figure is about 75%. By the same token the Tables show that the number of persons exposed to more than 40 events per day is, as would be expected, greatest under the noise sharing regime.

The N70 computations in the Tables only include areas within the 40 events per day contour as this broadly equates to the 20 ANEF (55 Leq) contour for Sydney and this therefore allows a ‘like for like’ comparison to be made between the PEI/AIE approach and the ANEF approach in the worked example.

The outer contour on the N70s shown in Chapter 4 extends to 10 events per day in order to maximise the coverage of the information. It is important that this difference in ‘cut-off’ level is not overlooked when making comparisons between different PEIs.

The analysis has been based on the N70. If a detailed analysis were being carried out, a similar table would need to be produced for, say the N80 (number of events above 80 dB(A)), to ascertain the consistency of the noise exposure patterns at different single event levels.

In order to address the above issues and ensure clarity when using the PEI and AIE it is more robust to express them in the form PEI(x,y) and AIE(x,y) where ‘x’ is the dB(A) value and ‘y’ is the number of events ‘cut-off’ value.

Table C. 1: PEI( 70) and AIE Values—Comparison of Operating Arrangements at Sydney Airport

No of Events
>70 dB(A)
PRE-PARALLELS PARALLELS NOISE SHARING
No of persons exposed No of Person-Events AIE No of persons exposed No of Person-Events AIE No of persons exposed No of Person-Events AIE
>200 750 187,500 250 10,500 2,625,000 250 100 25,000 250
150–200 1,750 306,500 175 10,000 1,750,000 175 700 122,500 175
100–150 22,000 2,750,000 125 15,500 1,937,500 125 5,500 687,500 125
50–100 42,000 3,150,000 75 25,000 1,875,000 75 58,000 4,350,000 75
40–50 14,000 630,000 45 9,500 427,500 45 37,500 1,687,500 45

Notes

  1. The number of person-events for each exposure zone has been calculated by multiplying the population in each zone by the mid-point N70 value for each range. Hence AIE—the average individual exposure—in this case is the mid-point N70. A more accurate approach would b e based on assigning census populations to INM grid points for which N70 values have been computed. The information in the Table is only indicative.

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Table C. 2: Cumulative PEI( 70) and AIE Values Comparison of Operating Arrangements at Sydney Airport

No of Events
>70 dB(A)
PRE-PARALLELS PARALLELS NOISE SHARING
No of persons exposed No of Person-Events AIE No of persons exposed No of Person-Events AIE No of persons exposed No of Person-Events AIE
>200 750 187,500 250 10,500 2,625,000 250 100 25,000 250
>150 2,500 494,000 198 20,500 4,375,000 213 800 147,500 184
>100 24,500 3,244,000 132 36,000 6,312,500 175 6,300 835,000 133
>50 66,500 6,394,000 96 61,000 8,187,500 134 64,300 5,185,000 81
>40 80,500 7,024,000 87 70,500 8,615,000 122 101,800 6,872,500 68

Notes

  1. The cumulative values for exposed population and number of person-events shown in the Table have been derived from the partial values shown in Table 3A. (2) AIE—the average individual exposure—is calculated by dividing the number of person-events by the population exposed.

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C. 2 Using the PEI to analyse partial noise loads

The PEI is very useful for considering partial noise loads. The PEI can be calculated for just one movement, or a small number of movements, to produce a result that is meaningful. For example, it was shown in Section 5.5 how the noise load generated by one flight at Sydney can be very easily compared to the total daily noise load generated at other airports.

A good example of examining partial noise loads is to compare the two most commonly used, and highest capacity, runway operating modes at Sydney Airport (Mode 9—northerly parallel flow & Mode 10—southerly parallel flow). Figures 4.8 and 4.9 in Chapter 4 show the ‘worst day’ N70s for these two modes.

A PEI/AIE analysis has been carried out on the noise distribution for these two ‘worst days’ and the key information is summarised in Table C.3 along with data for the 1995 and 1998 average days for comparative purposes.

Table C. 3 Summary of PEI Analysis for Partial Noise Loads

Exposure for persons within the N70 contours 1998 Average Day
(LTOP)
Mode 10 Day
(approx 2.5 days/month)
Mode 9 Day
(approx 2.5 days/month)
1995 Average Day (parallels)
No of persons exposed to more than 10 events louder than 70 dB(A) 269,500 110,000 332,500 142,500
No of persons exposed to more than 150 events louder than 70 dB(A) 1,100 23,000 800 21,000
No of Person-Events (x 10 6) 8.7 8.6 10.8 9.9
Average number of noise events louder than 70 dB(A) for persons within the 10 events contour 32 79 33 69

Notes

  1. The figures for the 1995 Average Day (parallel runway regime) are based on an N70 which extends to 10 events/day. The figures shown in Table 5.1 for the parallel runway regime only extend to the 40 events/day contour to allow comparison with the population within the 20 ANEF.

Comparison of the data in the table for the ‘Mode 9 Day’ with the ‘Mode 10 Day’ reveals an excellent example of noise sharing versus noise concentration

  • on a Mode 9 day more than 3 times the number of persons are within the 10 events N70 contour
  • on a Mode 10 day the average noise load per person is approximately 2.5 that under Mode 9 (79 events cf 33 events).

Tables C.4 and C.5 contain the detailed PEI/AIE workings and show that the total noise load (expressed as PEI for persons within the 10 events/day contour) generated by Mode 9 is approximately 20% greater than that generated by Mode 10

  • on the Mode 9 day less than 10% of the noise load is imposed on areas where there are more than 100 movements
  • on the Mode 10 day about 65% of the noise load is on areas where there are more than 100 movements
  • the greatest noise load for the Mode 9 day is in the 20–50 movements range; for the Mode 10 day it is in the 100–200 movements range.

In summary Mode 9 generates a greater total noise load and more people are exposed to noise but the average individual noise load is much lower than under Mode 10.

Table C.3 also shows that under the parallel runway regime the noise exposure regime on an average day was broadly similar to that on a Mode 10 ‘worst day’ which now only occurs on about 2.5 days per month on average.

This example illustrates that the PEI/AIE approach enables the differences between scenarios to be clearly drawn out. If the analysis were based on ANEF information, due to the logarithmic base of the ANEF, the differences between the two modes would not appear to be as stark and the output not as clearly understood given the non-relational nature of the units.

Figures C.1 and C.2 show continuous functions of the PEI/AIE information in Tables C.4 and C.5.

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Table C. 4 PEI( 70) and AIE Values Comparison of Sydney Airport LTOP Modes

No of Events
>70 dB(A)
1998 AVERAGE DAY MODE 9 DAY MODE 10 DAY
No of persons exposed No of Person-Events % of total PEI AIE No of persons exposed No of Person-Events % of total PEI AIE No of persons exposed No of Person-Events % of total PEI AIE
>200 719 185 242 2.1 258 353 86 565 0.8 245 5 017 1 102 081 12.8 220
100–200 9 174 1 062 299 12.3 115 6 044 734 983 6.8 121 28 668 4 344 253 50.6 152
50–100 31 504 2 249 297 25.8 71 52 918 3 412 551 31.6 64 25 590 1 854 034 21.6 72
20–50 114 238 3 623 798 41.6 32 154 597 4 864 955 45.0 31 29 799 999 318 11.7 34
10–20 113 723 1 588 968 18.3 14 118 594 1 707 682 15.8 14 19 841 284 275 3.3 14
TOTAL 269 358 8 709 334 100.0 32 332 506 10 806 736 100.0 33 108 915 8 583 961 100.0 79

Notes

  1. The number of person-events has been obtained by multiplying the number of persons exposed by the number of events above 70 dB(A). It has been calculated by assigning census populations to INM grid points for which N70 values have been computed. The information in the Table is only indicative.

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Table C. 5 Comulative PEI( 70) and AIE Values Comparison of Sydney Airport LTOP Modes

No of Events
>70 dB(A)
1998 AVERAGE DAY MODE 9 DAY MODE 10 DAY
No of persons exposed No of Person-Events % of total PEI AIE No of persons exposed No of Person-Events % of total PEI AIE No of persons exposed No of Person-Events % of total PEI AIE
>200 719 185 242 2.1 258 353 86 565 0.8 245 5 017 1 102 081 12.8 220
>100 9 893 1 247 541 14.3 126 6 397 821 548 7.6 128 33 685 5 446 334 63.4 161
>50 41 397 3 496 838 40.2 84 59 315 4 234 099 39.2 71 59 275 7 300 368 85.0 123
>20 155 635 7 120 636 81.8 46 213 912 9 099 054 84.2 42 89 074 8 299 686 96.7 93
>10 269 358 8 709 334 100.0 32 332 506 10 806 736 100.0 33 108 915 8 583 961 100.0 79

Notes

  1. The cumulative values for exposed population and number of person-events shown in the Table have been derived from the partial values shown in Table C.4. AIE—the average individual exposure—is calculated by dividing the number of person-events by the population exposed.
  2. ‘Mode 9 Day’ and ‘Mode 10 Day’ refer to a day when these parallel modes were used for more than 15 hours. The data in the tables derived from the movements on sample days—8Jan 1999 for the ‘Mode 9 Day’ and 20 Jan 1999 for the ‘Mode 10 Day’.

Figure c.1

Figure c.2

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Last Updated: 9 July, 2014