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1. METHOD OF MEASUREMENT The measurement is performed at microphone positions 2 and 6 as shown in Figure 1 of the Appendix, with the vehicle stationary. The highest A-weighted sound level shall be registered during venting the pressure regulator and during ventilating after the use of both the service and parking brakes. The noise during venting the pressure regulator is measured with the engine at idling speed. The ventilating noise is registered while operating the service and parking brakes; before each measurement, the air-compressor unit has to be brought up to the highest permissible operating pressure, and then the engine switched off.

2. EVALUATION OF THE RESULTS

For all microphone positions two measurements are taken. In order to compensate for inaccuracies of the measuring equipment, the metre reading is reduced by 1 dB(A), and the reduced value is taken as the result of measurement. The results are taken as valid if the difference between the measurements at one microphone position does not exceed 2 dB(A). The highest value measured is taken as the result. If this value exceeds the sound level limit by 1 dB(A), two additional measurements are to be taken at the corresponding microphone position. In this case, three out of the four results of measurement obtained at this position have to comply with the sound level limit.

3. LIMITING VALUE The sound level shall not exceed the limit of 72 dB(A). Appendix Figure 1: Microphone positions for measurement of compressed air noise The measurement is performed at the stationary vehicle in accordance with Figure 1, using two microphone positions at a distance of 7 m from the contour of the vehicles and at 1,2 m above ground.