Several studies have examined ionospheric variation associated with meteorites, meteoroids, or meteors based on Global Satellite Navigation System total electron content observations. However, there have been few quantitative studies of the D-region of the ionosphere (60–90 km), which is associated with meteoroids. We investigated variations in the D-region during the passage of a fireball over Hokuriku, Japan, at 14:33 UT on 23 April 2023 and a satellite re-entry at 12:38 UT on 26 December, 2023, using OCTAVE very low-frequency (VLF, 3–30 kHz) and low-frequency (LF, 30–300 kHz) transmitter signals. OCTAVE is an observation network of VLF/LF transmitter signals from low to high latitudes that we established. In this study, we used three transmitters, BPC (68.5 kHz), JJY (60.0 kHz), and JJI (22.2 kHz), observed at Rikubetsu observatory (RKB), Japan. Periodic variation of 200–500 s was observed in the amplitudes and phases of BPC–RKB path at the acoustic wave arrival times. Periodic variation of 300–500 s was observed in the amplitudes and phases of JJY60–RKB path at the arrival time of acoustic wave. For JJI–RKB path, there was no clear variation, because variation with a period of 200–300 s occurred before the arrival time of the acoustic waves. Based on the observed propagation time of the acoustic waves and ray tracing results, the acoustic waves or atmospheric gravity wave propagated obliquely from fireball trajectory up to a D-region height.