I think this is a clear case of someone reading some numbers an not knowing what they mean, in summary a A321-200 is much quieter than a 747-300.
A 747-300 with a TOW 377,800 kg and CF6-80C2B1 has the following noise characteristics relative to Chapter 3
Flyover - 6.9
Sideline - 4.6
Approach - -0.2
Cumulative - 11.3
An A213-200 with a TOW 93,000 kg and V2533A5 has the following noise characteristics relative to Chapter 3
Flyover - 4.6
Sideline - 2.4
Approach - 5.5
Cumulative - 12.5
Above numbers from
http://www.aci.aero/aci/aci/file/ACI...ties/Environment/ACINoiseIndex.pdf
But what does relative to Chapter 3 mean ?
We need to look at ICAO Annex16, Volume I, Attachment A
Between a TOW of 35 and 400t, the sideline noise is defined as 80.87 + 8.51 log(TOW)
747-300 = 80.87 + 8.51 log (377.8) = 102.80 EPNdB
321-200 = 80.87 + 8.51 log (93.0) = 97.62 EPNdB
747-300 margin over chapter 3 is 4.6 = sideline noise generated is 102.80 - 4.6 = 98.20 EPNdB
321-200 margin over chapter 3 is 2.4 = sideline noise generated is 97.62 - 2.4 = 95.22 EPNdB
A321-200 is 2.98 EPNdB quieter
Between a TOW of 35 and 280t, the approach noise is defined as 86.03 + 7.75 log(TOW), above 280t it is a flat 105
747-300 = 105 EPNdB
321-200 = 86.03 + 7.75 log (93.0) = 101.29 EPNdB
747-300 margin over chapter 3 is -0.2 = approach noise generated is 105 + 0.2 = 105.2 EPNdB
321-200 margin over chapter 3 is 5.5= approach noise generated is 101.29 - 5.5 = 95.79 EPNdB
A321-200 is 9.41 EPNdB quieter
Between a TOW of 48.1 and 385t, the flyover noise for twin engine aircraft is defined as 66.65 + 13.29 log(TOW)
Between a TOW of 20.2 and 385t, the flyover noise for four engine aircraft is defined as 71.65 + 13.29 log(TOW)
747-300 = 71.65 + 13.29 log (377.8) = 105.90 EPNdB
321-200 = 66.65 + 13.29 log (93.0) = 92.81 EPNdB
747-300 margin over chapter 3 is 6.9 = flyover noise generated is 105.90 - 6.9 = 106.10 EPNdB
321-200 margin over chapter 3 is 4.6 = flyover noise generated is 92.81 - 4.6 = 87.31 EPNdB
A321-200 is 18.79 EPNdB quieter
In summary,
the 747-300 has a 11.3 EPNdB cumulative margin over chapter 3, the 747-300 chapter 3 cumulative limit is 313.70 EPNdB
the 321-200 has a 12.5 EPNdB cumulative margin over chapter 3, the 321-200 chapter 3 cumulative limit is 291.72
EPNdB
The A321-200 is 31.19 EPNdB cumulatively quieter than a 747-300, as expected.
[Edited 2007-08-31 21:20:40]