Abstarct: In many of the previous researches about the acoustic noise radiated from electrical machines, the effects of structural parameters are discussed. Nevertheless, there is a great debate about the effect of operational parameters on acoustic noise characteristics radiated from the electrical machines. This research aims to study the effect of operational parameters and brief comparison between the acoustic noise radiated from induction and synchronous motors. For this purpose, a wound-rotor induction motor has been chosen as a test motor. Consequently, with the aim of investigating the effect of operational parameters, the analytical formulae are represented and then evaluated with experimental results. Moreover, this research studies the noise source identification methods. Firstly, the dominant noise source of the test motor has been located by scanning the sound pressure values over the surrounding area around the test motor. This method has been used in many researches. Furthermore, a novel method has been presented to identify the dominant noise sources. In the proposed method, the experiments have been accomplished in three different modes. In each mode, one of the operational parameters including speed, terminal voltage, and field current has been considered as independent variable whose value varies linearly with time in a predetermined range. Simultaneously, the sound pressure radiated from the test motor has been measured and saved. The post-processing analysis then accurately determined the dominant noise sources of the test motor.