Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p45
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 131072–133877

shall be used.

2.3. Conditions of measurement

2.3.1. Condition of the motorcycle

         Before the measurements are made the motorcycle engine shall be brought to the normal operating temperature.

         If the motorcycle is fitted with fans with an automatic actuating mechanism, this system shall not be interfered with during the sound measurements.
         During the measurements the gearbox shall be in neutral gear. If it is impossible to disconnect the transmission, the driving wheel of the motorcycle shall be allowed to rotate freely, for example by placing the vehicle on its centre stand.

2.3.2. Test site (See appendix - figure 2)

         Any area in which there are no significant acoustic disturbances may be used as a test site. Flat surfaces which are covered with concrete, asphalt or some other hard material and are highly reflective are suitable; surfaces consisting of earth which has been tamped down shall not be used. The test site must be in the form of a rectangle whose sides are at least 3 m from the outer edge of the motorcycle (handlebars excluded). There shall be no significant obstacles, e.g. no persons other than the rider and the observer may stand within this rectangle.
         The motorcycle shall be positioned within the said rectangle so that the microphone used for measurement is at least 1m from any kerb.
2.3.3. Miscellaneous

         Readings of the measuring instrument caused by ambient noise and wind effects shall be at least 10 dB(A) lower than the sound levels to be measured. A suitable windshield may be fitted to the microphone provided that account is taken of its effect on the sensitivity of the microphone.

2.4. Method of measurement

2.4.1. Nature and number of measurements

         The maximum sound level expressed in A-weighted decibels (dB(A)) shall be measured during the period of operation laid down in paragraph 2.4.3.
         At least three measurements shall be taken at each measuring point.

2.4.2. Positioning of the microphone (See appendix - figure 2)

         The microphone shall be positioned level with the exhaust outlet or 0.2 m above the surface of the track, whichever is the highest. The microphone diaphram shall face towards the exhaust outlet at a distance of 0.5 m from it. The axis of maximum sensitivity of the microphone shall be parallel to the surface of the track at an angle of 45 degrees +/- 10' to the vertical plane of the direction of the exhaust emissions.
         In relation to this vertical plane, the microphone shall be located on the side which gives the maximum possible distance between the microphone and the outline of the motorcycle (handlebars excluded).
         If the exhaust system has more than one outlet at centres less than 0.3 m apart, the microphone shall be