Appendix C—PEI Computations

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

C.1 Detailed computations for the &lsquoWorked Example’
C.2 Using the PEI to analyse partial noise loads

C. 1 Detailed computations for the &lsquoWorked 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 Events >70 dB(A)	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

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.

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 Events >70 dB(A)	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

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.

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

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.

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 Events >70 dB(A)	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

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.

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 Events >70 dB(A)	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

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.
‘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