This document specifies methods for recording the time history of instantaneous sound pressure in several positions around rotor powered unmanned aircraft systems (UAS) with a maximum take-off mass (MTOM) of less than 150？kg in accordance with ISO 21895^[9]. The UAS can be either electrically powered or fuel-powered. It is not applicable to the tilt-rotor or tilt-wing UAS. It does not account for the UAS noise certification or regulation

This document can also be applied to measure the sound pressure from a UAS with either multiple rotors or a single rotor.

This document specifies:

a)？recommendations and requirements for three different test facilities for the noise measurements of various categories of multirotor-powered UAS:

—？requirements and recommendations of UAS noise tests in anechoic chambers (Clause？7);

—？requirements and recommendations of UAS noise tests in anechoic wind tunnels (Clause？8);

—？requirements and recommendations of UAS noise tests in outdoor environments (Clause？9);

b)？requirements and recommendations for the configuration of noise measurement for multirotor-powered UAS in hover, vertical take-off and landing, and horizontal cruise;

c)？recommendations for the test configuration and procedures to minimize the influence of meteorological effects.