Perception-based noise assessment of a future blended wing body aircraft concept using synthesized flyovers in an acoustic VR environment—The ARTEM study

Kurzfassung

New aircraft concepts are currently being developed with the goal of less emissions of CO2 and noise. Remarkable noise reductions in long-range aircraft can only be expected from disruptive vehicle designs, new propulsion systems and specific low-noise technologies. In this paper, one such future vehicle design, a blended wing body (BWB) long-range aircraft, is described and studied with respect to sound levels on the ground, sound characteristics and noise annoyance. Virtual flyovers of different vehicle variants were synthesized and auralized in an acoustic VR environment, and investigated through psychoacoustic laboratory experiments. The applied methodology was successfully hierarchically validated by comparison with measurements of existing jet aircraft, assessing acoustical indices, time-frequency features, perceived plausibility, and induced noise annoyance. The perception-based evaluation of the BWB revealed that, while the BWB aircraft may initially be perceived as somewhat more unfamiliar, they are substantially less annoying than current tube-and-wing long-range aircraft of similar range and mission for take-offs as well as for landings. For the best BWB variant, noise annoyance was reduced by 4.3 units for departures and by 3.5 units for approaches on the 11-point scale. The main reason for these findings seems to be the acoustic shielding by the body of the extended fuselage, which was found to be an important factor in reducing sound levels in the order of 10–20 dB, and accordingly also to strongly reduce loudness. Additional low noise technologies and geared turbofan engines with a high bypass ratio further contributed to the reduction of noise annoyance of the BWB. A large part of the BWBs benefit could be explained by its lower sound levels, but additional benefits were found. The observed reduction in noise annoyance was found to be larger than what can be explained with conventional noise metrics. This benefit is probably due to more favorable sound characteristics compared to today's reference aircraft, such as less variation in time and less audible tones. The current study thus suggests that the studied BWB vehicle concept may substantially reduce noise annoyance on humans.