BS ISO 13325:2019 pdf download – Tyres — Coast-by methods for measurement of tyre-to-road sound emission 7 Instrumentation 7.1 Instrumentation for acoustical measurements The sound pressure level meter or equivalent measuring system, including the windscreen recommended by the microphone manufacturer, shall meet the minimum requirements of a Class 1 instrument in accordance with IEC 61672-1 and/or IEC 61672-3. Alternatively, IEC 60651 1) may be used. The measurements shall be made using the frequency weighting, A, and the time weighting, F. The calibration of the sound pressure level meter shall be checked and adjusted in accordance with the manufacturer’s instructions or with a standard sound source (e.g. pistonphone) at the beginning of the measurements and rechecked and recorded at the end of them. The calibration device shall meet the requirements of Class 1 in accordance with IEC 60942. If the sound pressure level meter indications obtained from these calibrations differ by more than 0,5 dB during a series of measurements, the test shall be considered invalid. Any deviation shall be recorded in the test report.At intervals of not more than two years, the sound pressure level meter shall be verified with the requirements of IEC 61672-1 and/or IEC 61672-3. Alternatively, IEC 60651 may be used [5] . At intervals of not more than one year, the calibration device shall be verified with the requirements of IEC 60942. Windscreens shall be used in accordance with the microphone manufacturer’s recommendations. When no general statement or conclusion can be made about conformance of the sound level meter model to the full specifications of IEC 61672-1, the apparatus used for measuring the sound pressure level shall be a sound level meter or equivalent measurement system meeting the compliance requirements of Class 1 instruments as described in IEC 61672-3. NOTE The tests of IEC 61672-3 cover only a limited subset of the specifications in IEC 61672-1 for which the scope is large (temperature range, frequency requirements up to 20 kHz, etc.). It is economically not feasible to verify the whole IEC 61672-1 requirements on each item of a computerized data acquisition systems model. Apparently, until today, no computerized data acquisition system available complies with the full specifications of IEC 61672-1. It is beyond the possibilities of the users of these systems to prove conformity of the instrumentation required by the test code. 7.2 Microphones Two microphones shall be used in the test, one on each side...
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