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er340790
27th Sep 2007, 14:42
BA Quote: 'Both the A380 and B787 are rated as producing a quarter of the noise level of the B747-400.'

Can anyone out there confirm whether this is indeed true? And if so how does it relate to real-world sound levels? Somehow I suspect that if Joe Public was standing at the end of the runway as it performs a MTOW take-off over him, he would NOT experience 75% less noise than a 744.

Explanations please.....

Zeke
27th Sep 2007, 18:08
The comment is indeed true.

The EASA approved noise levels for jet aeroplanes TCDSN (Issue 2) http://www.easa.eu.int/doc/Certification/Design_Appro/Noise/odoc/TCDSN%20Jets%20(070831).xls shows the worst A380 (A380-841 569,000 MTOW 391,000 MLW Rolls-Royce Trent 970) has a cumulative noise footprint of 287.7 EPNdB, the worst 744 is (747-400 396,894 MTOW 295,743 MLW Pratt & Whitney PW 4056 (FB2T)) cumulative noise footprint is 306.0 EPNdB, the worst RR powered 744 is the (747-400 394,626 MTOW295,743 MLW Rolls-Royce RB211-524H2) with a cumulative noise footprint of 302.1 EPNdB.

Cumulative noise footprints for the three cases was calculated with the following data obtained from measurement (worst case data for types listed):
A380-841 Lateral 94.9 EPNdB, Flyover 94.8 EPNdB, Sideline 98.0, certified chapter 4 with Annex 16/I
744-PW4056 (FB2T) Lateral 99.7 EPNdB, Flyover 101.6 EPNdB, Sideline 104.7, certified chapter 3 with Annex 16/I
744-RB211-524H2 Lateral 98.7 EPNdB, Flyover 99.6 EPNdB, Sideline 103.8, certified chapter 3 with Annex 16/I

The 14.4 EPNdB cumulative difference between the noisiest A380, and the RR powered 744 comes out to be about 24% of the 744 noise level, which to me makes the "rated as producing a quarter of the noise level of the B747-400" as being a valid comment. BA would not need the highest MTOW configuration for their network, so the difference would actually be larger.

In terms of Joe Public, more of the 85 dB contour stays within the airport boundary, and out of the nearby residents houses.

When talking about noise, you are looking at a log scale, measured by a computer, and in the aircraft case they use an Effective Perceived Noise Level which takes into account the increased annoyance with single frequencies, such as the tones emanating from the compressor of turbofan engines

The A380 in its heaviest certified form has been measured to generate as much noise as a 767-300/300ER RB211-524G, A300-B4-203 CF6-50C2, A300-F4-622R PW 4158, A310-203 CF6-80A3, A310-324 PW 4152, A330-301 CF6-80E1A2, A340-643 Trent 560 EP, and is quieter than the BA 777s.

"Somehow I suspect that if Joe Public was standing at the end of the runway as it performs a MTOW take-off over him, he would NOT experience 75% less noise than a 744."

Well they will experience significantly less power going into their ears and damaging them.

Mäx Reverse
27th Sep 2007, 21:49
The A380 was performing wake-turbulence trials at an airfield (EDMO - Oberpfaffenhofen for those who care) some 15 kilometers to the west of my hometown in July 2006. So I grabbed my Digicam and went there.

The big bus and an Lufthansa B744 were flying about 50 patterns alternatively over the airport while the wake vortices were measeured by LIDAR from the ground. They were going around from about 200-400 feet (my guess) in various configurations.

My first impression was indeed how silent the bus is compared to the jumbo. However I don't know the AUWs and thrust levels used on both aircraft.

Regards MAX

Jimmyjimjim
27th Sep 2007, 23:41
-3dB=Half the energy/power required.
-5dB =Half the ear damage.
-10dB=Half the percieved loudness.

In the case of the 380 I would speculate this would translate to(very roughly)

75% reduced energy dissapated to sound energy.
50% reduced ear fatigue/damage
25% reduced percieved loudness.

Glad to be able to contribute.
Self loading Sound Engineer here.

nick2007
28th Sep 2007, 03:42
Was noticeably quieter than a 747 when it came by Sydney last year. Whether 'noticeably' = 75% is another matter.

ZAGORFLY
28th Sep 2007, 10:31
I can hear and see from my office desk 747s passing everyday on their SID over Hong Kong. when the 380 did his 2 fly by sure the engines were not in Climb but it was quite silent indeed.
78% more silent could be if you consider that its enormous wing allow the plane to be more far from the ground than a 747 in the same Leigh of distance.

stiffwing
28th Sep 2007, 12:52
Open question... Is it correct to say that there is only reverse on the inboards? If so, is there MEL relief for an inoperative reverser, and how is the braking system augmented for landings at such a high MLW.