This study aims i) to determine the effect of Dundubia manifera insect sound on the stomata opening area of corn plant (Zea Mays L.) at frequencies of (in Hz) 3000, 3500, 4000, 4500, and 5000, and ii) to know the peak frequency that can optimize the stomata opening of the corn plant. The insect sound has been manipulated into peak frequencies and validated using Octave 4.2.1 software. The experiment uses one corn-field for the treatment and control plants. Sampling is taken three times, i.e.: 15 minutes before sound exposure, during sound exposure for 30 minutes, and 15 minutes after sound exposure. The stomata opening area is observed using a microscope by observing the output via NIS Elements Viewer program. The length and width of the stomata openings are measured using Image Raster 3.0 and the area of the stomata opening is calculated using the elliptic equation. This study shows that the stomata opening area when given sound exposure is larger than without sound exposure. The largest stomata opening area is obtained at a frequency of 3000 Hz, viz.: 93.7 µm².