  Several industry leaders and governmental agencies are currently
investigating the use of Unmanned Aerial Vehicles (UAVs), or drones as commonly
known, for an ever-growing number of applications from blue light services to
parcel delivery. For the specific case of the delivery sector, drones can
alleviate road space usage and also lead to reductions in CO2 and air pollution
emissions, compared to traditional diesel-powered vehicles. However, due to
their unconventional acoustic characteristics and operational manoeuvres, it is
uncertain how communities will respond to drone operations. Noise has been
suggested as a major barrier to public acceptance of drone operations in urban
areas. In this paper, a series of audio-visual scenarios were created to
investigate the effects of drone noise on the reported loudness, annoyance and
pleasantness of seven different types of urban soundscapes. In soundscapes
highly impacted by road traffic noise, the presence of drone noise lead to
small changes in the perceived loudness, annoyance and pleasantness. In
soundscapes with reduced road traffic noise, the participants reported a
significantly higher perceived loudness and annoyance and a lower pleasantness
with the presence of the same drone noise. For instance, the reported annoyance
increased from 2.3 (without drone noise) to 6.8 (with drone noise), in an
11-point scale (0-not at all, 10-extremely). Based on these results, the
concentration of drone operations along flight paths through busy roads might
aid in the mitigation of the overall community noise impact caused by drones.
