O que os fabricantes fazem para reduzir o ruído da cabine?

it is being claimed by the Airbus that their new planes offer more sound proofing than those of Boeing

Eu acho que você quer dizer este tipo de reivindicação :

No matter where they sit, all passengers benefit from the quiet A380 cabin with on average half the sound energy of other aircraft. Passengers' feedback confirms the extraordinary contribution to their general well-being due to the absence of background noise on the A380.

In market research surveys the A320 is regularly rated higher than its rivals for the low level of noise in its cabin. Effective insulation in the cabin is one reason why passengers say they find the A320 a quiet aircraft in which to fly. The A320 cabin is the subject of continuous improvements and in its latest version, the noise has been reduced by a further 1dB.

how do Airplane manufacturers tackle the problem of soundproofing the cabin

Existem vários métodos

• materiais de isolamento acústico na parede da fuselagem entre peles internas e externas.
• escolha de materiais e móveis internos etc.
• ajuste dos contornos interiores da cabine para permitir uma menor velocidade de fluxo de ar.
• aerodinâmica da fuselagem.
• forros acústicos de nacele de motor.
• bordas recortadas no bico de exaustão do motor.
• ventoinhas do motor maiores e mais lentas.
• sharklets.
• etc

BBC relatório

One of the main sources of noise is wind. So during the design phase of modern aircraft, computational tools model the aerodynamics of the aeroplane to highlight areas of high airflow that are likely to increase cabin noise. This allows engineers to reshape their designs, says Alan Pardoe, director of product marketing at Airbus. Such techniques, he says, helped the double-decker Airbus A380 plane to be recognised by the UK Noise Abatement Society as the quietest jet airliner on the market.

O Airbus diz

When it comes to making the A380 one of the quietest aircraft in the sky, it's the small details that count... in fact, more than 3 million of them!

This is the number of tiny perforations in acoustic linings on the large nacelles that surround and protect the A380’s jet engines. The acoustic material helps dampen noise created by the airliner’s four turbofan powerplants, ensuring the A380 is a friendly neighbour wherever it operates in the world. The A380’s nacelles are supplied by Aircelle, which has worked closely with Airbus in minimising the jetliner’s noise output during takeoff and landing. Acoustic panels are applied throughout the engine – from the air inlet to the exhaust nozzle.

Each panel, which is produced from composite material or titanium, is designed to attenuate noise at different frequencies, further improving the soundproofing effect. Noise-reducing innovations include Aircelle’s 2-degree-of-freedom acoustic panels, which use a stack of two honeycomb composite sandwich layers separated by a porous wall.

These panels dampen high-frequency noise from the engine turbines. With much of this noise source successfully dampened by the acoustic treatment, engineers and designers are now focusing their attention on treating other sources of aircraft noise, promising even quieter jetliners for the future.

e também isso

The Airbus-developed Zero-Splice engine nacelle liner was designed to reduce the noise generated by the jet engines’ large fan, which represents almost half the noise during both approach and take-off. Following extensive studies carried out by Airbus on how to reduce fan noise, it was found that splices used to join the engine nacelle inlet’s acoustic panels generated forward fan noise – which was counter-efficient to the liner’s acoustic treatment. Airbus therefore developed the Zero-Splice nacelle liner as a single 360 deg. piece of composite, which is comparable in size to the diameter of an A320 fuselage.

É óbvio que as medidas que reduzem o ruído do motor no solo também o reduzem na cabine.

Eles também escrevem sobre como os sharklets de asas reduzem o ruído.

Eu acho que existem muitas outras medidas e opções de design que são introduzidas para reduzir o ruído.

What proportion of the total aircraft development cost ...

Eu ficaria surpreso se a Airbus ou a Boeing tornassem público qualquer quebra de seus custos de desenvolvimento.

Você pode encontrar detalhamentos gerais como o seguinte, mas ainda não encontrei nenhum que rompa os custos de desenvolvimento de isolamento acústico.

Estritamente para a série DC-9 / MD-80, existem dois métodos disponíveis.

Um é o sistema de sincronização do motor que sincroniza um mecanismo com o outro para evitar o som de zumbido quando os motores não estão funcionando com a mesma configuração. Existem dois modos N1 e N2. O sistema compara as velocidades dos dois motores e ajusta o motor esquerdo para coincidir com o motor certo. Quando o interruptor do sistema é desligado, o sistema continua a sincronizar os motores usando o EPR.

O outro é um sistema de redução de ruído ativo que adiciona novos suportes de motor projetados para reduzir o ruído.

link

LORD HAS RECEIVED US certification for its NVX active noise-and-vibration control system on the McDonnell Douglas DC-9 and MD-80. The company says that its system is the first to be approved for use on large commercial aircraft, and "...is being considered for several DC-9/MD-80 installation programmes." Approval follows installation of the NVX on a corporate MD-87.

The system consists of actuators on the engine-mounting yoke which counteract engine vibration and so reduce cabin noise. The actuators are driven continuously by a controller based on cabin-noise data from microphones installed behind the trim or under the floor.

The results are most noticeable in the aft cabin, where engine tones typically measure 20dB above background noise, says Lord, adding: "The NVX Active System eliminates these tones on the ground, as well as during take-off, cruise and descent." Programme manager Becky Weih says that noise levels are so reduced that the rear of the cabin "...is no louder than the front". Erie, Pennsylvania-based Lord says the NVX has been approved on several corporate-aircraft types.