Retrofits deliver major progress in reducing aircraft noise

Retrofits deliver major progress in reducing aircraft noise
by Robert Schreiber
Berlin, Germany (SPX) Mar 25, 2025

Aircraft noise continues to impact communities near airports, but researchers at the German Aerospace Center (DLR) have made important strides in mitigating this problem. As part of the Low Noise ATRA (LNATRA) initiative, DLR scientists have shown that strategic modifications to existing aircraft can result in measurable reductions in noise pollution.

A key outcome of the LNATRA project was the achievement of a three-decibel decrease in flyover noise. "We were able to reduce noise at individual sources, such as the landing gear and the edges of the landing flaps, by up to six decibels," said Michael Pott-Pollenske from the DLR Institute of Aerodynamics and Flow Technology. He further explained, "For people on the ground, this corresponds to a perceived noise reduction of around 30 percent."

These conclusions stem from extensive flight testing performed between 2016 and 2019 at Magdeburg-Cochstedt Airport using the A320 Advanced Technology Research Aircraft (ATRA). The aircraft underwent retrofitting with eight noise-reduction technologies, including specially contoured engine exhaust nozzles, porous materials along landing flap edges, and partial coverings for the landing gear.

Acoustic data were collected via an array of 30 ground microphones distributed over a 120 by 340 metre area. This was supplemented with wind tunnel experiments and digital simulations, enabling accurate comparison with baseline measurements from 2016 flights without retrofits.

Pott-Pollenske noted that the alignment of simulation, wind tunnel, and flight test data affirmed the robustness of their approach: "Our results from flight tests, earlier wind tunnel experiments and simulations are in good agreement." He added, "This confirms that our years of research into noise sources were well directed and that the transfer to real aircraft was successful." According to Pott-Pollenske, only NASA and JAXA have achieved similar advancements on an international scale.

While the retrofits contribute to noise mitigation, they also present challenges such as increased aircraft weight, which could elevate fuel usage. However, DLR researchers suggest this can be counteracted through aerodynamic innovations. Pott-Pollenske pointed to laminar flow technology, which reduces drag, as an example.

Balancing environmental concerns with noise abatement remains central to DLR's strategy. "Noise can be detrimental to health, which is why noise research remains a vital part of our work," Pott-Pollenske emphasized. "Our findings can make a significant contribution to making aviation quieter and more sustainable."

The LNATRA project results are being integrated into broader research efforts like the 'LU(FT)2 2030' initiative, which incorporates human perception of noise into design considerations. Pott-Pollenske noted the role of simulations: "By continuously refining our simulations, we will be able to design quieter aircraft digitally in the future." This process will enable noise protection to be built into aircraft from the design phase using simulated assessments of sound emissions.

DLR's continued focus on noise reduction supports the European Commission's goal of achieving a 65 percent decrease in aircraft noise levels by 2050 compared to the year 2000. DLR researchers believe that quieter and environmentally responsible air travel is within reach and remains an essential aim for future aviation.