Annex 3 Methods and instruments for measuring the sound emitted by L1 category vehicles 1. Measuring instruments 1.1. Acoustic measurements 1.1.1. General The apparatus used for measuring the pressure level shall be a sound level meter or equivalent measuring system meeting the requirements of Class 1 instruments (inclusive of the recommended windscreen, if used). These requirements are described in IEC 61672-1:2013. Measurements shall be carried out using the time weighting "F" of the acoustic measuring instrument and the "A" frequency weighting curve also described in IEC 61672-1:2013. When using a system that includes periodic monitoring of the A-weighted sound pressure level, a reading should be made at a time interval not greater than 30 ms. The instruments shall be maintained and calibrated in accordance with the instructions of the instrument manufacturer. 1.1.2. Calibration At the beginning and at the end of measurement session, the entire acoustic measuring system shall be checked by means of a sound calibrator that fulfils the requirements of Class 1 sound calibrators according to IEC 60942:2003. Without any further adjustment, the difference between the readings shall be less than or equal to 0.5 dB(A). If this value is exceeded, the results of the measurements obtained after the previous satisfactory check shall be discarded. 1.1.3. Compliance with requirements Compliance of the sound calibrator with the requirements of IEC 60942:2003 shall be verified once a year. Compliance of the instrumentation system with the requirements of IEC 61672-1:2013 shall be verified at least every 2 years. All compliance testing shall be conducted by a laboratory which is authorized to perform calibrations traceable to the appropriate standards. 1.2. Instrumentation for speed measurements The rotational speed of the engine shall be measured with an instrument meeting specification limits of at least ±2 per cent or better at the engine speeds required for the measurements being performed. The road speed of the vehicle shall be measured with instruments meeting specification limits of at least ±0.5 km/h when using continuous measuring devices. If testing uses independent measurements of vehicle speed, this instrumentation shall meet specification limits of at least ±0.2 km/h.
Annex 3 Methods and instruments for measuring the sound emitted by L1 category vehicles 1. Measuring instruments 1.1. Acoustic measurements 1.1.1. General The apparatus used for measuring the pressure level shall be a sound level meter or equivalent measuring system meeting the requirements of Class 1 instruments (inclusive of the recommended windscreen, if used). These requirements are described in IEC 61672-1:2013. Measurements shall be carried out using the time weighting "F" of the acoustic measuring instrument and the "A" frequency weighting curve also described in IEC 61672-1:2013. When using a system that includes periodic monitoring of the A-weighted sound pressure level, a reading should be made at a time interval not greater than 30 ms. The instruments shall be maintained and calibrated in accordance with the instructions of the instrument manufacturer. 1.1.2. Calibration At the beginning and at the end of measurement session, the entire acoustic measuring system shall be checked by means of a sound calibrator that fulfils the requirements of Class 1 sound calibrators according to IEC 60942:2003. Without any further adjustment, the difference between the readings shall be less than or equal to 0.5 dB(A). If this value is exceeded, the results of the measurements obtained after the previous satisfactory check shall be discarded. 1.1.3. Compliance with requirements Compliance of the sound calibrator with the requirements of IEC 60942:2003 shall be verified once a year. Compliance of the instrumentation system with the requirements of IEC 61672-1:2013 shall be verified at least every 2 years. All compliance testing shall be conducted by a laboratory which is authorized to perform calibrations traceable to the appropriate standards. 1.2. Instrumentation for speed measurements The rotational speed of the engine shall be measured with an instrument meeting specification limits of at least ±2 per cent or better at the engine speeds required for the measurements being performed. The road speed of the vehicle shall be measured with instruments meeting specification limits of at least ±0.5 km/h when using continuous measuring devices. If testing uses independent measurements of vehicle speed, this instrumentation shall meet specification limits of at least ±0.2 km/h.
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