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An acoustic test system with 84 microphones was developed to construct a noise hemisphere for Urban Air Mobility (UAM) based on flight test measurements. The system was installed on the runway at the Korea National Aviation Test Center (KNAC) to evaluate an electric-powered unmanned helicopter (EUH) during flight tests. Over 30 level flights at various altitudes and speeds were conducted, acquiring time-based acoustic signals. These signals were then depropagated to reconstruct the noise hemisphere. The analysis showed that by combining data from tests with different flight directions and altitudes under low wind conditions, dense scattered data can be obtained for a wide angular range in the noise hemisphere. The constructed noise hemispheres reasonably represent the aircraft's noise characteristics according to its speed.
Cho et al. (Thu,) studied this question.