Document ID: chunk:federal_register_of_legislation:F2006L01279:body:0:p9
Version: federal_register_of_legislation:F2006L01279
Segment Type: other
Provision Reference: 
Character Range: 25209–27918

in use. No person or object other than the person conducting the test and an observer or the objects necessary for the performance of the test shall be within 3m of the microphone in use.
    3.1.5   Before the measurements are begun, the engine shall be brought to its normal operating conditions as regards: temperatures, tuning, fuel, sparking plugs, carburettor(s), etc. as appropriate.
    3.1.6   The use of special acoustic shielding may be permitted in unusual cases. Refer to paragraph

3.2   Microphone position.
    3.2.1   The microphone shall be directed towards the orifice of the exhaust outlet and shall be supported by a tripod or similar device not providing excessive acoustic reflection.
    3.2.2   The nominal axis of maximum sensitivity of the microphone shall be substantially parallel to the test site surface.
    3.2.3   The height of the microphone above the test site surface shall be equal to that of the orifice of the exhaust outlet + 25 mm but shall not be less than 200 mm above the test site surface.
3.2.4   The distance of the microphone from the orifice of the exhaust outlet shall be:
3.2.4.1  in the case of a 'Goods Vehicle' or 'Omnibus'  1050 mm + 50 mm,
3.2.4.2  in the case of any other vehicle 525 mm +25 mm.

    3.2.5   For vehicles fitted with one exhaust outlet which is at a height above the test site surface of less than 1500 mm, the nominal axis of maximum sensitivity of the microphone shall make an angle of 45 degrees + 10 degrees with the principal direction of the gas flow from the exhaust outlet.
3.2.5.1 In selecting this microphone position the microphone shall be placed so that the
greatest possible distance is achieved between it and the vehicle.

    3.2.6   For vehicles fitted with one exhaust outlet which is at a height above the test site surface of at least 1500 mm, the nominal axis of maximum sensitivity of the microphone shall make an angle of 90 degrees + 10 degrees with the longitudinal centreline of the vehicle.
3.2.6.1 In selecting this microphone position the microphone shall be placed so that the
greatest possible distance is achieved between it and the vehicle.

    3.2.7   For vehicles fitted with two or more exhaust outlets spaced less than 500 mm apart and connected to a single silencer only one microphone position shall be used. That position shall be selected in accordance with the procedure described in the preceding paragraphs in respect of an exhaust outlet which results in the microphone being at the greatest possible distance from the vehicle.
    3.2.8   For vehicles fitted with two or more exhaust outlets connected to separate silencers or spaced more than 500 mm apart, each exhaust outlet shall be