Using Differential Spectral Analysis to Identify Tornado Infrasound Signatures

Tornadoes emit infrasound (i.e., sound at frequencies below human hearing) that can propagate over long distances within the Earth’s atmosphere. However, attenuation and other local infrasound sources make it extremely difficult to identify the spectral content associated with a tornado. During the 2024 tornado season, our team had a 4-sensor array deployed near the Oklahoma State University campus. The current work included all 200+ tornadic events within 500 km of the array during the deployment, including several that were relatively close with an orientation that favored ground-based detection. Range dependent infrasound propagation modeling was performed to identify tornadic events with favorable propagation patterns to the array. Differential spectral analysis was then used to identify spectral content that was amplified (or attenuated) from the direction of the tornado, which is an indication of the potential tornado signature. This presentation provides a summary of the methods used to identify the infrasound signature and examples of favorable and non-favorable events.