Drone Noise Insights

2 december 2019

Unmanned Aerial Vehicles (UAV’s) are becoming more common. And as the number of drone sightings around airports is increasing, it is safe to say that introducing UAV’s in our infrastructure will come with a substantial set of issues. Implementing them, therefore requires a thorough impact analysis of a variety of aspects: operational, economical, safety, security and non the least environmental. Adecs Airinfra Consultants is diving into the environmental aspect and tries to highlight and define the scale of impact of UAV’s.

Should UAV noise be considered an issue?

One of the aspects of the environmental impact is noise, which is an important one for airports. Studies have shown that although drone noise is not as dominant as noise from manned aircraft, it is however determined as an annoyance effect on people exposed to it. Now, looking at a future where Urban Air Mobility will be part of daily life, one can imagine the amplified reaction to the buzzing sounds of numerous drones constantly flying around. So, before the drone integration process begins, UAV noise must first be understood, complete with all its influencing factors and parameters.

What is our project focused on?

Adecs Airinfra Consultants is working in cooperation with TU Delft’s Aircraft Noise and Climate Effects Department to shed light on UAV acoustics. Because we feel that clear legal guidelines need to be substantiated with thorough investigation into the matter. That is why we perform acoustic measurements of a preselected set of drones. The aim is a comprehensive analysis of the behaviourism of drone noise in different operational contexts such as hover, forward flight and increasing and decreasing altitudes. Parallel to this, we analyse the overall sound level originating from the drone, in relation to various design elements i.e. size, weight, the number of rotors, and so on. Knowing the sound levels exerted by these UAV’s, can lead to proper measures from regulatory bodies as well as the ability to give potential clients (airports, training centers, etc.) an overview on the impact of implementing frequent drone flights on their premises.

How can we come to an empirical model for all types?

As opposed to winged aircraft, rotorcraft such as helicopters and drones do not exhibit consistent flight profiles. Therefore, noise models such as the one from the ECAC.CEAC cannot be readily applied to rotorcrafts. These vehicles are prone to influences from external factors (weather conditions), variability in design elements, as well as their unpredictable flight paths. Other current models require usage of expensive and complex Computational Fluid Dynamics (CFD) tools, along with a profound comprehension of theoretical aerodynamics. But these models only quantify the impact of a single type of drone, limiting its applicability to other archetypes.

The only viable process in this situation seems to be creating empirical models using extensive measurements. Therefore, observing the sound behaviour with varying parameters of interest such as blade numbers, rotor numbers, thrust and velocity, and many more, is the only way to construct a prototype of an empirical model.

What is our goal?

The objective of our project is to lay the foundations for understanding drone noise and to pave the way for future possibilities of easily and accurately determining UAV noise effects, similarly to how it is already done for aircraft. Although this approach of determining UAV noise levels might have its deficiencies, it will for sure be a first important step for developments to come. The outcomes will also give a complete overview of drone behaviourism and hopefully help improve the current preliminary legislative measures that are been taken.

Adecs Airinfra Consultants will help set one of the stepping stones for ways of safely and lawfully coping with what seems to be a fast approaching future.

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