Fire Lines Volume 15, Issue 4
FIRE SCIENCE
Acoustic observations of a prescribed burn
Authors: Omar Marcillo, Jonathan M. Lees, Kara Yedinak, Keith Bourne, Brian Potter, Steven Flanagan, Joseph O'Brien, Joseph Paki
Researchers conducted an acoustic monitoring study during a prescribed fire at Eglin Air Force Base, Florida, to investigate the feasibility of using sound—particularly infrasound—as a tool to track fire dynamics. The study deployed a network of infrasound sensors outside the 5.5 km² burn unit and radiometer sensors within it to measure heat release. By analyzing sound signals in the low-frequency (between around 20 and 200 Hz) and infrasonic (below 20 Hz) ranges the team aimed to determine whether acoustic emissions from the active combustion zone could track fire behavior remotely, even in conditions where traditional line-of-sight tools (e.g., infrared cameras) might fail due to smoke or topography. The data collection focused on both combustion noise and interference from operational sources like helicopters, which were systematically filtered out to isolate signals from the fire itself.
The results revealed that prescribed fire emits coherent, measurable acoustic energy in low-frequency bands that correspond to the fire's spatial and temporal progression. Distinct acoustic pulses were observed at different stations in sync with the ignition sequence and peaks in Fire Radiative Power, confirming that sound can trace fire movement. Through array processing, researchers were able to determine the direction of propagation of signals, or backazimuth, and align them with known locations of fire ignition and progression, particularly in regions with distinct vegetation types like patches of evergreen forest. The most coherent combustion-related signals came from areas with sustained heat release, suggesting a strong relationship between vegetation characteristics, combustion intensity, and acoustic output.
