These days almost everyone has either flown a drone or heard the nasty whine they generate. Although small drones (up to 20 kg) are about 40 decibels quieter than traditional civil aircraft, they make a high level of noise – which people find very annoying.
A NASA study found that drone noises were more disruptive than those from road vehicles. And my own research has shown that the noise from drones is less preferred than that from civil aircraft – even at the same volume.
Part of the problem is that drones often fly at relatively low altitudes in overpopulated areas that are normally not exposed to aircraft noise. This is likely to create tension within the exposed communities. If not adequately addressed, the noise issues could undoubtedly affect the wider acceptance and commercialization of drones and jeopardize the significant societal benefits they could bring.
For example, small to medium-sized drones are already being used for various applications, e.g. B. for medical supplies and searching for missing persons. Another innovation in commercial aviation is the development of electric vertical take-off and landing vehicles (and possibly autonomous vehicles) to transport people around cities.
Various aircraft manufacturers are currently developing several vehicles for “urban air mobility” or “flying taxis”. Both drones and flying taxis make sounds that are very different from traditional civil aircraft and have similar problems with noise nuisance.
In 2019, I started a line of research aimed at answering two big questions: How will communities respond to these new vehicles with unconventional sound signatures when they operate on a large scale? And how can the design of these new vehicles be improved to protect the health and quality of life of the people in these communities?
To answer the first question, we examined how a drone operation can affect the perception of a number of typical sound environments in cities. Since drones cannot be flown closer than 50 m to humans, highly realistic scenarios were created with the help of virtual reality techniques in which a drone hovers in a selection of urban locations.[Read: Meet the 4 scale-ups using data to save the planet]
This laboratory study found that the noise produced by hovering a small quad-copter significantly affects the perception of the sound environment. For example, a significant increase in noise pollution has been reported when the drone is hovering, especially in places with little traffic. This suggested that the noise from road traffic might make the noise from drones less noticeable. The use of drones on busy roads could therefore reduce the increase in noise pollution in the community.
We are now testing a large number of drones with different operating maneuvers. We are trying to better understand and predict human responses to the drone sounds and to collect meaningful evidence to further develop the regulation of the sounds they make.
By integrating human responses into the design process, the most undesirable noises can be avoided in the earliest stages of vehicle development.
This can be done either directly through subjective tests (human participants assessing a series of drone noise samples and providing feedback) or through the use of so-called psychoacoustic metrics, which are widely used in the automotive industry. These metrics enable an exact representation of how different sound characteristics (pitch, temporal variations, tones) are perceived. We want to use them to inform about the design of drones. For example, optimize the position of the rotors so that drones sound less annoying.
The combination of virtual reality techniques and psychoacoustic methods to inform about the design and operation of drones avoids costly and inefficient ad hoc corrections in later phases that go beyond the traditional approach to assessing aircraft noise. More importantly, however, when drone manufacturers incorporate these strategies into their designs, they may just build machines that are not only efficient but also a little less irritating.
This article has been republished under a Creative Commons license by Antonio J Torija Martinez, acoustics professor at Salford University from The Conversation. Read the original article.
Read on: New breathtaking HD images show the largest canyon in our solar system