A great earthquake (Mw = 8.3) and aftershock (Mw = 7.4) occurred near Hokkaido, Japan on September 25, 2003. This earthquake and aftershock were sources of local and epicentral infrasound signals observed at two seismo-acoustic arrays in the Republic of Korea. Local infrasound results when seismic signals near the receiver couple to the atmosphere. The local cross coupling from seismic ground motion to infrasound signal at two seismo-acoustic arrays enabled us to compute a seismic-to-infrasound transfer function at each array. The observed transfer function quantifies the microphone response when the seismometer response is known. When seismometers and infrasound gauges are collocated, this procedure can provide field calibration.