Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p22
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 66576–69636

than 1dB(A) the maximum sound level authorized for the category of vehicle tested, a second series of two measurements at the corresponding microphone position shall be made. Three out of the four results so obtained in this second position must fall within the prescribed limits.
            To allow for lack of precision in the measuring instrument the figures read from it during measurement shall each be reduced by 1dB(a).

           3.2. Measurement of noise emitted by stationary vehicles

           3.2.1. Sound level in the vicinity of vehicles

            In order to facilitate subsequent checks on vehicles in use, the sound level must be measured close to the exhaust system outlet in accordance with the following requirements and the measurement results entered in the test report drawn up for the purpose of issuing the certificate referred to in annex 1.

           3.2.2. Acoustic measurements

            A precision sound level meter as defined item 1.1 must be used for the measurements.

           3.2.3. Test site - local conditions (figure 2)

           3.2.3.1. Measurements should be made on a stationary vehicle in an area which corresponds to that for measurements of vehicles in motion and therefore corresponds to the provisions given in annex 8 to this Regulation.

           3.2.3.2. During the test nobody shall be in the measurement area, except the observer and the driver whose presence must have no influence on the meter reading.

           3.2.4. Disturbance noise and wind interference

            Readings on the measuring instruments produced by ambient noise and wind must be at least 10 dB(A) below the sound level to be measured. A suitable windscreen may be fitted to the microphone provided that account is taken of its effect on the sensitivity of the microphone.

           3.2.5. Measuring method

           3.2.5.1. Nature and number of measurements

            The maximum sound level expressed in A-weighted decibels [dB(A)] must be measured during the operating period referred to in paragraph 3.2.5.3.2.1.
            At least three measurements must be taken at each measuring point.

           3.2.5.2. Positioning and preparation of the vehicle

            The vehicle shall be located in the centre part of the test area with the gear lever in neutral position and the clutch engaged. If the design of the vehicle does not allow this, the vehicle shall be tested in conformity with the manufacturer's prescriptions for stationary engine testing. Before each series of measurements, the engine must be brought to its normal operating condition, as specified by the manufacturer.
            If the vehicle is fitted with fan(s) having an automatic actuating mechanism, this system shall not be interfered with during the sound level measurements.

           3.2.5.3. Measuring of noise in proximity to the exhaust (see appendix, fig. 2)

           3.2.5.3.1. Positions of the microphone

           3.2.5.3.1.1. The height of the microphone above the ground should be equal to that of