This study aims at identifying transmission noise of two types of electrical vehicles with different transmission systems using the developed two-dimensional dynamic signal analysis (2DSA). Two electrical scooters, more specifically, with a gear transmission system and a continuous variable transmission (CVT) system, respectively, have been taken as test benches due to the whistle-like noise emitting from their transmission systems. To effectively process dynamic signatures measured from rotary machinery with varying speed, and even varying orders during operation, such as a machine with a CVT system or gear-shifting operation, the 2DSA approaches including the order analysis (OA) and the time-frequency analysis have been developed and implemented as processing tools. The specifications of vehicle transmission systems, especially the ratio of each speed reduction, and the tooth (cog, blade, etc.) number of transmission elements, i.e., geometric analysis, are firstly to be examined. After the 2DSA processes the noise measured from test vehicles during wide-open-throttle operation, dominant annoying transmission noise components can be extracted, and their sources can be identified through comparing feature orders obtained from geometric analysis. The procedure can not only identify noise sources but conclude transmission components to be further modified in respect of annoying noise.