Noise mapping system with acoustical measurement blimp robot

To measure environmental noise in our living space, a lot of noise measurement and mapping systems have been studied. However, it is costly because many measurement points are needed to make a noise map. There are problems such as a measurement area reachable by human hands is limited. In recent years, with advances in unmanned aerial vehicle (UAV) technology, various types of UAV have been developed. When UAV is used to acoustical measurement, it can automatically acquire information such as the environmental noise not only on the ground but also in the air. Multirotor aircraft is frequently used as UAV, however, it causes loud noise as it must always rotate propellers during flying. In this paper, a noise mapping system with acoustical measurement blimp robot is proposed. The proposed system which is silent type of multirotor for acquisition of environmental noise is constructed. The total length of the system is 1.4 m, and the weight is about 1.4 kg. The system has six propellers to move omnidirectionally, and a system control board with a field-programmable gate array (FPGA) which integrates CPU for controlling propeller rotations, sound recording, communicating with host PC, and obtaining the information of the system motion. The proposed system requires positional information to make a noise map. Thus, simultaneous localization and mapping (SLAM) technique are applied for the positional tracking by using image signal processing. To evaluate our system, a preliminary experiment in the large room was conducted to make a simple three-dimensional noise map. The results show that the propeller rotation noise level was reduced 47 dB as compared with a general multirotor, and it could make a three-dimensional indoor noise map by combining the sound information and the positional information.