14:00
Session 14: Auralization and Acoustic Simulation
Chair: Siddhartha Krishnamurthy
14:00
20 mins
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Preliminary assessment of active noise cancelling techniques for drone acoustic emissions
Jan Adam Wanatowicz, Roberto Merino-Martinez
Abstract: Unmanned Aerial Vehicles (UAVs) are among the fastest-growing sectors of the aerospace industry. As drones become prevalent in densely populated urban areas, they pose a significant risk of increasing noise pollution. Despite having lower sound power than conventional aircraft, UAV noise is often perceived as more annoying due to its prominent high-frequency content and tonal components.
While traditional noise mitigation relies on hardware design, such as rotor synchronization or blade geometry, recent research highlights the potential of Active Noise Control (ANC) techniques. Because global control of the sound field is physically limited, especially at higher frequencies, this study proposes an onboard ANC system designed to create a localized "quiet zone" beneath the vehicle. In practice, this quiet zone could be selected depending on the application of interest. To evaluate this, an adaptive real-time control algorithm was developed for integration with a DJI Mavic 3 Enterprise drone.
Experimental validation will be conducted in the anechoic chamber at Delft University of Technology, using microphone and speaker arrays mounted to the UAV fuselage. Samples will be gather at the intended "quiet zone" and outside of it to examine possible interference. Acoustic performance of different ANC techniques will be quantified in terms of conventional and sound quality metrics, using the Sound Quality Analysis Toolbox (SQAT) to evaluate loudness, sharpness, tonality, roughness, and fluctuation strength. Furthermore, subjective annoyance ratings will be gathered through psychoacoustic listening tests. The results are expected to serve as proof of concept and evaluate the efficacy of localized ANC in improving the psychoacoustic profile of UAV operations.
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14:20
20 mins
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On the psychoacoustic impact of synchrophasing for distributed propellers and ducted fans
Stephen Schade, Maximilian Marggraf, Roberto Merino-Martinez, Karl-Stéphane Rossignol, Sébastien Guérin
Abstract: This study examines whether synchrophasing and stator clocking can reduce tonal noise emissions in distributed propulsion systems under realistic flight conditions. Using measurement-informed auralization, we evaluate two configurations: an eight-propeller tilt-prop aircraft and a tilt-duct system with 26 fans. For the distributed propellers, results demonstrate that synchrophasing at specific phase angles (e.g. half propeller blade-to-blade angle) induces destructive interference at the blade-passing frequency and its harmonics, leading to sound pressure level reductions of approximately 10 dB and a reduction of tonality and fluctuation strength larger than one just-noticeable difference compared to in-phase operation. For the ducted fans, an evolutionary optimization routine determines optimal stator clocking positions to minimize tonal interaction noise. This approach achieves tonal noise reduction of approximately 10 dBA at centerline certification positions. Whereas the optimized stator distribution successfully lowers centerline noise levels by creating a narrow low-tonal noise corridor beneath the flight path, a significant lateral reduction (e.g. for surrounding communities) could not be achieved. The findings establish phase control and stator clocking as viable, yet sensitive, degrees of freedom for minimizing tonal noise in distributed propulsion systems.
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