Insulated gate bipolar transistor (IGBT) is the key power electronic device in the field of new energy power generation, smart grid and high voltage power transmission. The condition monitoring of IGBT is the basis for reliability monitoring of power electronic devices. Existing detection methods based on electromagnetic thermal parameters are difficult to meet the needs of fast, non-destructive, and online detection at the same time. In the switching state, mechanical stress wave signals generated due to the interaction of electromagnetic forces within the IGBT with multiple physical fields. The characteristic parameters of the signals can characterize the state of IGBT effectively, so it has the potential to become a new IGBT state monitoring method in the future. This paper studies the acoustic emission signals generated by different switching states of the IGBT under low voltage conditions from three aspects: signal generation mechanism, test system construction, and test result analysis. It is concluded that the IGBT generates acoustic emission signals both at the moments of switching on and switching off. The main components and frequency range of the signal are obtained. The peak of the acoustic emission signal pulse at the time of conducting is linearly related to the collector voltage V_CE. High frequency electromagnetic waves are related to VCE. The pulse width affects the density of frequency points and acoustic emission signals even generated without V_CE.