5.2 Criteria for the adequacy of the test environment5.2.1 Accuracy grade 1 (precision)5.2.1.1 IndoorsA suitable test environment is a hemi-anechoic room as specified in ISO 3745.5.2.1.2 OutdoorsA suitable test environment is a plane area outdoors with hard ground (concrete, asphalt or similar surfaces) and no reflecting objects in the near vicinity.For the purposes of this International Standard, an object is considered as sound-reflecting if three conditions are fulfilled:a) its width (e.g. diameter of a pole or supporting member) exceeds one-tenth its distance from the reference box;b) it is not covered with absorbing material;C) either, having an acoustically smooth surface, the object is arranged in such a way as to reflect sound like a mirror towards the microphone position or its surface texture gives rise to diffuse reflection (reflection of sound in many directions).Assessment of item c) requires advanced expertise.The distance between a reflecting object and the closest point of the sound source under test or the distance between a reflecting object and the microphone position shall be: