Purpose. Improving the technology of maintenance of wheelsets of passenger cars using the onboard monitoring system and the acoustic monitoring method. Methodology. Field studies of the acoustic monitoring method were conducted in accordance with the requirements of the current standards using a professional sound recorder. The initial data were analyzed using the licensed software, acoustic signal envelopes were computed using the Hilbert transform, and the values of the peak factor of the acoustic signal from the interaction of the wheel and the rail in the frequency bands were calculated. Findings. The methods for detection of damages of wheelsets in the railways of different countries were analyzed and an alter native approach to monitoring the technical condition of wheelsets in motion of cars was proposed. Field investigations of the acoustic monitoring method were conducted, the obtained data were processed and analyzed, informative diagnostic signs were defined. The results of the study were used for programming and configuring the acoustic monitoring device for wheelsets. Originality. For the first time, the noise emission sources of cars were investigated experimentally during operational move ment, the noise sources of the rolling stock were classified, and informative diagnostic signs of a signal for the detection of wheel damage were discovered and calculated using the acoustic monitoring method. Practical value. A model of the acoustic monitoring device was developed and configured based on experimental studies and subsequent calculations, which allowed reducing the number of sensors per car and improving their operational conditions. Labo ratory tests of the developed device were conducted.