Vad gör tillverkare för att minska kabinbuller?

6

Airbus hävdar att deras nya flygplan erbjuder mer ljudisolering än Boeings, och jag själv observerade detsamma. Hur hanterar flygplanstillverkare problemet med ljudisolering av stugan, för att minska bullret som når inuti från planet (motorn låter och bruset fritt ström)? Vilken andel av den totala flyutvecklingskostnaden skulle detta vara (ungefär säga för en Airbus 320 och Boeing 777)?

    
uppsättning Damalani Singh 24.06.2015 11:49

2 svar

8

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

Jag antar att du menar den här typen av krav :

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

Det finns en mängd olika metoder

  • ljudisoleringsmaterial i fuselagens vägg mellan inre och yttre skinn.
  • Val av inredningsmaterial och inredning mm
  • Inställningshyttens inre konturer för att tillåta lägre luftflödeshastighet.
  • flygplans aerodynamik.
  • akustiska linjer för motor nacelle.
  • skulpterade kanter på motorns avgasmunstycke.
  • större långsammare motorfläktar.
  • sharklets.
  • etc

BBC rapport

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.

Airbus säga

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.

och också detta

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.

Det är enligt min uppfattning självklart att åtgärder som minskar motorbuller på marken också minskar det i stugan.

De skriver också om hur vingeharkar reducerar brus.

Jag skulle gissa att det finns många andra åtgärder och designval som introduceras för att minska buller.

What proportion of the total aircraft development cost ...

Jag skulle bli förvånad om Airbus eller Boeing offentliggör någon uppdelning av deras utvecklingskostnader.

Du kan hitta generella uppdelningar som följande men jag har inte hittat några som bryter ut ljudisoleringskostnader.

    
svaret ges 24.06.2015 12:50
3

Strängt för DC-9 / MD-80-serien finns två metoder tillgängliga.

En är motorns synkroniseringssystem som synkroniserar en motor till den andra för att förhindra dronningsljudet när motorerna inte körs i ganska samma inställning. Det finns två lägen N1 och N2. Systemet jämför hastigheterna för de två motorerna och justerar den vänstra motorn för att matcha rätt motor. När systemströmbrytaren är avstängd, fortsätter systemet SYNC motorerna med EPR.

Den andra är ett aktivt brusreduceringssystem som lägger till nya motorupphängningar som utformats för att minska bullret.

länk

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.

    
svaret ges 24.06.2015 16:35