Sonic bloom was a technology that used sound waves at 07.00–11.00 a.m. in the western part of Indonesia with a particular frequency to stimulate plant growth. This study aims to determine the effectiveness and best time for applying the foliar fertilizer with sound waves to cabbage plants. This research was conducted in Kuta Gugung Village, Naman Teran District, Karo Regency, from September 1st, 2020, to December 9th, 2020. The research method was a non-factorial randomized block design with four treatments and five replications, namely: application sound waves without fertilization (control), fertilization at 1 hour before application sound waves, fertilization carried out simultaneously with application sound waves, and fertilization carried out 1 hour after application sound waves. The results showed that the application of foliar fertilizer with sound waves significantly affected stomata exposure, making fertilizer more effective. To get the best stomata exposure, it was at 8.30 a.m., but the average selling weight of the crop was not significant.