Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p16
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 50638–53733

requirements

            The compliance of the sound calibration device with the requirements of IEC 942:1988 shall be verified once a year and the compliance of the instrumentation system with the requirements of IEC 651, second edition shall be verified at least every two years, by a laboratory which is authorized to perform calibrations traceable to the appropriate standards.

           1.2.                                              Speed measurements

            The rotational speed of the engine and the vehicle speed shall be measured with instruments with an accuracy of +/- 2% or better.

           1.3.                                              Meteorological instrumentation

            The meteorological instrumentation used to monitor the environmental conditions shall include the following:
             (i)       A temperature measuring device which shall be accurate within +/- 1 degree C;
            (ii) a wind speed measuring device which shall be accurate within +/- 1.0m/s.

           2. CONDITIONS OF MEASUREMENT

           2.1. Site

           2.1.1. The test site must consist of a central acceleration section surrounded by a substantially flat test area.
            The acceleration section must be level; the track surface must be dry and such that rolling noise remains low.
            The test track must be such that the conditions of a free sound field between the sound source and the microphone are attained to within 1 dB. This condition shall be deemed to be met if there are no large sound-reflecting objects such as fences, rocks, bridges or buildings within 50 m of the centre of the acceleration section. The surface of the site must be in accordance with the provisions given in annex 8 to this Regulation and be free of powdery snow, tall grass, loose soil or cinders. There must be no obstacle which could affect the sound field within the vicinity of the microphone and the sound source. The observer carrying out the measurements must so position himself as not to affect the readings of the measuring instrument.

           2.1.2. Measurements shall not be made under adverse weather conditions. It must be ensured that the results are not affected by gusts of wind.
            Any sound peak which appears to be unrelated to the characteristics of the general sound level of the vehicle shall be ignored in taking the readings.

           2.1.2.1. The meteorological instrumentation should be positioned adjacent to the test area at a height of 1.2 +/- 0.1m.
            The measurements shall be made when the ambient air temperature is within the range from 0 degrees C to 40 degrees C.
            Tests shall not be carried out if the wind speed, including gusts, at microphone height exceeds 5m/s, during the sound measurement interval and shall be recorded during each test run.
            Values representative of temperature, wind speed and direction, relative humidity, and barometric pressure shall be recorded during the sound measurement interval.

           2.1.3. The A-weighted sound level of sound sources