permissible sound power level - logarithm of the ratio of a given sound power to the reference sound power. Power level in decibels is ten times the logarithm to the base ten of the ratio
Whereas the technical requirements which motor vehicles must satisfy pursuant to national laws relate, inter alia, to the permissible sound level and the exhaust system. ... If the inlet of the engine is fitted with an air filter which is necessary in order to ensure compliance with the permissible sound level, the filter shall be considered to be part of the silencer ...
