ISO 22868:2021 pdf download – Forestry and gardening machinery — Noise test code for portable hand-held machines with internal combustion engine — Engineering method (Grade 2 accuracy).
4 Quantities to be measured and quantities to be determined The quantities to be measured are the time averaged sound pressure levels defined in the relevant basic noise measurement standards (ISO 3744, ISO 11201), A-weighted and — if required — in frequency bands. The quantities to be determined are the sound power levels and the emission sound pressure levels, A-weighted and — if required — in frequency bands. 5 A-weighted sound power level determination For the determination of the A-weighted sound power level, ISO 3744 shall be used, subject to the following modifications or additions. a) The microphone array shall be six microphone positions, in accordance with Figure 1 and the coordinates described by Tables 1 and 2. NOTE 1 The six microphone array is permitted because experimental data have shown that use of this array does not yield results that differ significantly from those obtained with the 10 microphone array specified in ISO 3744. b) The measurement surface shall be a hemisphere with a radius, r, of ≥ 2 d O , preferably 4 m; d O is determined by the reference box and its defined location above ground, see Figure 1. If a bigger radius is needed it shall be chosen from 6 m, 8 m and 10 m. A smaller radius is permitted if it is demonstrated that the results are within 0,5 dB compared with measurements with a hemisphere of r = 4 m. NOTE 2 The smaller radius can be necessary in an anechoic room where a radius of 4 m cannot be provided. c) The conditions for the particular type of machine to be tested and its mounting and orientation shall be according to the corresponding annex of this document. d) Environmental conditions shall be within the limits specified by the manufacturer of the measuring equipment. The ambient air temperature shall be in the range −10 °C to 30 °C and the wind speed shall be less than 5 m/s. A microphone windscreen shall be used for all outdoor testing, and for indoor testing whenever the speed of ventilation air over the microphone exceeds 1 m/s.