This report compares the noise emission characteristics of motorcycles with noise emission for other vehicle types and attempts to evaluate the relevance of standard methods of measuring motorcycle noise emission for regulation test purposes. It was found that the noise emitted by motorcycles when operated at steady speed in top gear is governed by a single function of vehicle speed, the noise increasing by about 10 dB(A) for each doubling of road speed. This characteristic follows closely the generalised level speed function obtained for passenger cars operating freely in traffic. On dry road surfaces motorcycle rolling noise levels are generally substantially lower than the noise levels generated by the power unit. While there seems to be little opportunity to develop a noise test procedure which is commensurate with the wide range of in-use operating conditions for motorcycles, the results show that the full throttle acceleration test as described in EEC Directive 1015/78, although not perfect does meet the basic requirements of a regulation test procedure. However, further work on the full effects of the 1015 test procedure on a wider range of motorcycle types is desirable. The BS3425 test was not found to be suitable for use on high powered, large engine capacity, motorcycles. The EEC 1015 close proximity stationary test was found to fulfill the basic requirements of an in-use test procedure. The levels achieved under the test were found to be related to engine capacity, indicating that in-use limits should be set making some allowance for the larger engine capacity motorcycles. (A)

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