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2.11.6 Noise control
Due to the similarity of the piston stroke in different engine configurations within
the capacity classes, the noise test will be conducted at a fixed RPM. For
reference only, the mean piston speed at which the noise test is conducted is
calculated at 11 m/sec.
2 cylinders 3 cylinders 4 cylinders
600cc 5,500 RPM 6,500 RPM 7,000 RPM
750cc 5,500 RPM 6,000 RPM 7,000 RPM
over 750cc 5,000 RPM 5,000 RPM 5,500 RPM
2.11.7 The maximum sound level for engines with more than one
cylinder will be measured on each exhaust end.
2.11.8 A motorcycle which does not comply with the maximum
sound limits may be presented several times at pre-race control.
2.11.9 The surrounding sound must not exceed 90 dB/A within a 5
metres radius from the power source during tests.
2.11.10 Apparatus for noise control must be to international standard
IEC 651, Type 1.
The sound level meter must be equipped with a calibrator for control and
adjustment of the meter during periods of use.
2.11.11 The “slow response” setting must always be used.
2.11.12 Sound control after the competition
In a competition which requires a final examination of motorcycles before
the results are announced, this examination must include a sound control
measurement of at least the first three motorcycles listed in the final
classification. At this final test, there will be a 3 dB/A tolerance.
2.11.13 Noise control during a competition
In a competition which requires noise control tests during the event, motorcycles
must comply with the noise limits without the tolerance in Art. 2.14.13.
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