Other studies show a clear correlation peak at upper infrasound range (less than 20 Hz). A delay between the peak of auroral sounds and the peak of electromagnetic activity, corresponds to the speed of sound as if it were traveling from the auroral heights (80–100 km) to the Earth's surface.
Other studies demonstrate a strong correlation in the upper infrasound range (less than 20 Hz). There is a temporal relationship between the peak of auroral sounds and electromagnetic activity, which can be attributed to the speed of sound traveling from the auroral heights (80–100 km) to the Earth's surface.