The Robotics and Mechatronics group (UT-RaM) and the Engineering Fluid Dynamics group (UT-EFD) at the University of Twente have conducted the first successful noise measurements in collaboration with the innovation cluster for unmanned systems, Space53, located at Technology Base. Using a so-called microphone antenna, the acoustic emissions of an unmanned aerial vehicle, or drone, were quantified during various flight manoeuvres. The measurement system can quantify and localise noise by creating acoustic images of the noise produced. In addition, the unmanned aircraft is equipped with an experimental framework that allows relevant flight parameters, such as altitude, speed and position, to be read simultaneously and synchronised with the noise measurements. This framework allows the researchers to perform pre-programmed flight trajectories and manoeuvres, which significantly improves the repeatability of the noise measurements. 

Mike Holsheimer, Space53 programme manager, emphasises the importance of these measurements: ‘Besides driving innovations in the field of unmanned flight systems, social acceptance is also an important issue for us. Especially over densely populated areas, noise pollution can cause resistance. Thanks to accurate measurements of this kind, we will soon be able to adjust flight routes, altitudes and speeds to minimise noise pollution. This is a major breakthrough in the social acceptance of unmanned aircraft."

Silent aviation innovations

The advanced measurement system enables researchers to accurately quantify aircraft noise emissions, regardless of the type of aircraft; from unmanned aerial vehicles to electric air taxis and commercial aircraft. The UT-EFD research group conducts intensive research on the aeroacoustics of aircraft, as well as wind turbines, drones and ship propellers. To this end, experimental research is carried out in particular in the controlled environment of the University of Twente's silent wind tunnel. Research into noise emissions is of great importance for the environment and the living environment in the Netherlands, because it helps to reduce noise pollution, thus contributing to creating a healthier, sustainable and more pleasant living environment.   

Marijn Sanders, University Lecturer in the UT-EFD group, emphasises Twent Airport's optimal test environment: ‘Twente Airport is the ideal test location for noise measurements in the field. The airport is unique because of its low ambient noise level and limited air traffic, which offers accurate and extensive testing possibilities. Moreover, there is sufficient space and flexibility to test experimental innovations and adjust them where necessary if it turns out that certain aircraft designs or configurations produce too much noise. The mobile measurement system can be easily adapted and optimised, allowing repeated measurements until the desired noise production is achieved.  

Unmanned flight systems

Innovations in unmanned aviation and aerial robotics are rapidly succeeding each other. Electrically powered unmanned aircraft, which operate fully autonomously, are finding wider and wider applications such as cargo transport, object movement, surveillance and emergency response. It is likely that we will increasingly see and hear unmanned flight systems in our daily lives in the near future. 

As part of ongoing research projects led by Prof Antonio Franchi and Dr Chiara Gabellieri, the UT-RaM group is dedicating itself to the development and control of innovative multi-rotor flight systems equipped with tilted and actively tilting propellers. In these projects, unmanned flight systems are used, for example, to inspect ship spaces and control composite structures, such as aircraft and wind turbines. 

The noise production of an unmanned flight system is also an important aspect in other projects of the UT-RaM group where these systems are used for removing waste from rivers and delivering tools to people working at high altitudes. Chiara Gabellieri stresses, ‘Research into the design of control systems for autonomous air robots is essential to provide efficient and innovative solutions for different sectors. The acoustic assessment of these aerial robots is of great importance, especially given the UT-RaM group's focus on human-robot interaction and environmental applications. In addition, low noise production improves operational efficiency, making unmanned flight systems more suitable for use in densely populated urban areas, for example." 


Twente Airport as noise test site

Part of Technology Base, Twente Airport is the incubator for sustainable aviation. Electric-powered aircraft are known to be not only more sustainable, but also quieter. 

Peter Bulckaert, aviation consultant at Twente Airport: ‘Both in the development of components for electric aircraft and in the way they fly, there is still a lot to be gained in terms of noise reduction. We are therefore happy to make our runway and other test facilities available to carry out the necessary tests for these improvements. Also in the social acceptance of electric flying, the quieter the better, so it is a good addition for aircraft manufacturers to optimise both the components and the way of flying and in this way contribute to sustainable and quiet aviation."