QC/T 235-2008Technical requirements and test methods for exhaust silencers of motorcycles and mopeds (English PDF)

3.1 exhaust muffler

integral part used to exhaust the exhaust gas after engine combustion to the atmosphere and effectively reduce the noise of exhaust gas flow

Note: An exhaust muffler generally consists of the integral parts from the exhaust inlet to the exhaust port of the exhaust muffler, including the pollution control device and fiber sound-absorbing materials that may be installed on the exhaust muffler.

3.2 exhaust noise

noise generated when exhaust gas after engine combustion is discharged from exhaust port of exhaust device

3.3 measure of exhaust muffler

measure of engine power and exhaust noise to install the muffler to be test

3.4 hollow pipe

device that has the same boundary dimension and wall thickness as the muffler to be tested, does not contain all internal partitions, internal air ducts and tail end covers of the exhaust muffler, and has all welding process holes of the outer cylinder blocked

3.5 measure of hollow pipe

measure of engine power and exhaust noise to install the hollow pipe to substitute the exhaust muffler

3.6 insertion loss

difference of sound pressure levels of exhaust noise through the exhaust port during measure of hollow pipe and measure of muffler at the speed when the engine reaches the maximum net power, D, expressed in dB(A)

Note: Under normal circumstances, the size, shape and sound field distribution of the pipe orifice remain approximately the same, so the insertion loss is equal to the difference of noise sound pressure levels before and after installing the muffler at a given measuring point.

The insertion loss, D, shall be calculated using Formula (1):