The object under study is an impregnation process of wood of different species by exposure to acoustic ultrasound frequency vibrations. The purpose of the work is to intensify the impregnation process. Specimens of compacted and non-compacted birch and also of non-compacted aspen were impregnated by the immersion method and also using the thin layer mode. Water-based fire retardant of "Tent" brand was used as an impregnating mixture. Experiments showed that acoustic vibrations accelerated the impregnation process and increased the impregnation mixture weight fixed on the wood surface. The report analyzes the peculiarities of acoustic impregnation implemented by the immersion method and thin layer mode. The authors provide recommendations for selecting a layer thickness, angle of incident of an ultrasonic tool in the impregnating liquid and also mutual position of impregnation direction and vibrational displacement of the tool for the thin layer mode which proved to be the most effective. It was shown that the use of the thin layer mode allowed to implement the highquality impregnation of compacted birth.