10:30
Human Response to UAS and UAM Noise
10:30
20 mins
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Comparison of aircraft sounds in a simulated Living Room laboratory study
Naomi Sieben, Aleyandra Smitt, Roalt Aalmoes
Abstract: Annoyance of aircraft sounds is strongly related to loudness of the event, but perception also varies with sound type. To examine the annoyance of different aircraft sounds, a participants study was conducted to measure perceived annoyance while conducting a math task and a colouring task during playback of these sounds in a living room setting using a multi-speaker-based playback system. Outdoor sounds were translated towards indoor sound levels considering an open-window setting. Five different aircraft sounds were evaluated, two helicopter sounds, two jet aircraft sounds, and one drone sound, that also varied in between 64-80 dB(A) peak sound level, based on their recorded sound level and the reduction of sound due to the propagation to the indoor environment. The drone sound and one of the jet aircraft were similar in peak sound level and therefore directly comparable, the other sounds were louder. Participants reported perceived annoyance and perceived disturbance after each event. Results show no significant differences in annoyance during the colouring or math task for the different sounds. Reported disturbance for the math task was higher than for the colouring task. Both helicopters, that had a higher peak sound level, were considered more annoying than the drone. But the (higher peak sound level) Airbus A330 was not significantly more annoying than the drone, nor was the Boeing 737, which was equal in peak sound level as the drone. Both helicopters and the Airbus A330 were reported significantly more disturbing than the drone sound. This study shows that drone sounds are not more annoying than other aircraft sounds if the sounds are played according to the representative sound levels within the tested indoor setting. The calculated propagation of the sounds towards the indoor sound, where higher (drone) frequencies are more absorbed than lower frequencies, may contribute to these findings. Future studies examining this effect, as well as a study including a larger set of tested drone sounds, will help to clarify these assumptions.
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10:50
20 mins
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Listening to UAS swarms: exploring the impact of swarm configuration attributes on annoyance perception
Jithin Thilakan, Lukas Aspöck, Janina Fels
Abstract: The acoustic impact of Unmanned Aerial Systems (UAS), such as drones, has received increased attention in noise research in recent years due to their expanding uses in delivery, mapping, and surveillance applications. The emergence of ‘UAS swarms’, involving multiple UAS operated in coordinated formations, further intensifies the concerns regarding noise pollution and annoyance perception in urban environments. Systematically designed variations of swarm configurations, including spatial distribution, spectral characteristics, and temporal dynamics, can lead to different perceptual impressions and potentially lower annoyance levels. As a first step to explore these relationships, a pilot experiment was conducted in which individual swarm configuration attributes were systematically varied to examine their impact on annoyance perception. The examined attributes include the number of drones in a swarm, their spatial distribution, inter-drone spacing, swarm velocity, and pitch-modulations of sources. These were tested under two baseline conditions featuring swarms with dark and bright timbral characteristics, mimicking large and small drone types. A set of swarm flyover scenarios, featuring controlled variations of individual swarm attributes, was simulated in a free-field condition and auralized as binaural audio samples. Perceptual evaluation was carried out to analyse the differences in the perceived annoyance ratings across sets of audio samples created through variation of individual swarm attributes. Furthermore, the influence of swarm attribute variations on the conventional acoustic and perceptual sound quality metrics derived from the sound samples was explored, complementing the results of the listening experiment and contributing to the acoustic optimization of swarm configurations.
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11:10
20 mins
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Blade Number Effects in sUAS Rotor Noise Assessed Using Psychoacoustic Metrics and an Online Listening Test
Seokhyeon Shin, Yeongmin Jo
Abstract: Blade number is a key design variable in sUAS and Urban Air Mobility (UAM) rotors in both aerodynamics and acoustics, yet the blade-number-induced changes in the spectral and temporal acoustic characteristics may not be captured by overall sound pressure level (OASPL) alone. In this study, we compare psychoacoustic metrics with subjective annoyance obtained from an online listening test for sUAS rotor noise with varying blade number.
We obtained the noise data from the low Reynolds number rotor measurements conducted in the ISAE-SUPAERO anechoic chamber. Each rotor has a NACA 0012 airfoil, 0.25 m diameter, and a fixed pitch angle of 10° without any twist, while the number of blades varies from 2 to 4. The noise was recorded at 1.62 m using a 13-microphone semicircular array spanning −60° to 60°. The operating points were selected close to the theoretically required RPM to approximate an equal-thrust condition. The psychoacoustic metrics (loudness, sharpness, roughness, fluctuation strength, and tonality) and psychoacoustic annoyance (PA) based on More (2010) were computed using the MATLAB-based open-source code, Sound Quality Analysis Toolbox (SQAT).
At −60° direction, OASPL and N_5 changed little with blade number, whereas 〖PA〗_5 increased as blade number increased. This trend was consistent with the increased sharpness for higher blade numbers, partially offset by reduced tonality.
In an online listening test, 2-blade and 4-blade sounds at −60° direction were level-scaled to nominal levels of 60-80 dB in 5 dB steps (10 stimuli). Based on 41 valid responses, annoyance ratings did not differ significantly between blade numbers at 60-70 dB, while the 4-blade condition was rated significantly more annoying at 75-80 dB. In addition, the main annoyance factor selections changed from tonality/roughness for 2-blade to sharpness for 4-blade, which are qualitatively consistent with the objective metrics.
Based on these results, we conclude that psychoacoustic metrics can complement sound level metrics in trade studies of blade numbers for sUAS/UAM rotor noise.
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