Preliminary Investigation on Flyover Noise of Propeller-Powered Aircraft Using a Phased Microphone Array

With people’s heightened awareness of environmental protection, the noise level of large civil aircraft during take-off and landing are monitored with strict restrictions by the ICAO (International Civil Aviation Organization). This has triggered people’s interest in learning about the noise characteristics of aircraft components. Hence, researchers are developing phased microphone array test technology to analyze the characteristics of external noise sources of civil aircraft and verify the effect of noise reduction design. At present, most aviation research institutions around the world, have developed their own phased microphone array test technology. They have also carried out the corresponding flight noise test verification, widely used in aircraft low noise design and verification. To better understand the functioning of the external noise of civil aircraft and development the flight noise test capability of civil aircraft, COMAC Beijing Aircraft Technology Research Institute (BATRI) has also carried out the research on the flyover noise test technology. This research, based on a phased microphone array, has designed microphone array and built a set of phased microphone array test systems. For the research, a multi-arm spiral array with a diameter of 15 m and 84 channels were arranged, at the end of the runway of Zhanghe airport in Hubei Province. The domestic single-engine propeller-powered aircraft is used for multiple flights, such as different flight altitudes, different flight speeds, landing gear put-down, and retraction configurations. The test results provide effective test data. Based on this test data, Doppler effect correction is carried out on the flight test data, the test data of different working conditions are compared and analyzed by using the conventional Beamforming method and the noise source identification results are analyzed. The test data processing results show that the main noise source of single-engine propeller aircraft is the blade passing frequency noise of the propeller, and the pure tone noise has obvious characteristics, which are conducive to data correction. The results also indicate that the conventional beamforming noise source inversion algorithm can accurately identify the noise location. However, the sound source location accuracy has a certain deviation due to the influence of array design and aircraft flight condition control. This test has verified the microphone array test system, test process, data post-processing process, and accumulated field flight noise test experience. It also lays a foundation for later large-scale array and large-scale civil aircraft flight external noise source positioning tests.