Hidden Dangers Below the Water: Detecting Underwater Explosives with Sound Technology
Throughout the United States, numerous underwater locations—previously utilized as military training areas and weapon testing sites—conceal a perilous history. Beneath tranquil lakes, rivers, and coastal regions lie unexploded ordnance (UXO): bombs, torpedoes, and shells that failed to detonate as designed. These deteriorating munitions, now corroded and covered with marine organisms after years submerged, pose an unseen menace to swimmers, boaters, divers, and seaside communities.
An expanding array of scientific studies is now harnessing an effective tool—sound—to disclose what visual inspection cannot reveal. At the recent joint 188th Meeting of the Acoustical Society of America and the 25th International Congress on Acoustics in New Orleans, researchers unveiled new acoustic detection techniques that could transform the identification and safe extraction of these munitions.
The Heritage of Unexploded Ordnance in U.S. Waters
Over 400 identified underwater sites exist in the United States that might hold UXO. Many of these sites trace back to World War II and earlier, serving various military branches for practice bomb drops and weapon testing.
However, the boundaries and ownership of these sites have evolved over time. Coastal military installations have shut down, and waterfront zones—once restricted—are being transformed for recreational activities, tourism, and real estate growth. As more individuals engage in these waters for enjoyment, the likelihood of accidental encounters with UXO rises.
“These munitions may have been lying underwater for 70 or 80 years, deteriorating and gathering marine life,” stated Connor Hodges, a doctoral researcher at the University of Texas at Austin. “While they might appear to be harmless rocks or debris, disturbing them could cause unintended detonations or toxic leaks.”
Comprehending the Underwater Challenge
Detecting these decaying weapons is quite challenging. Standard visual surveys are not dependable because decades of corrosion and marine growth—like barnacles, algae, and other organic matter—render munitions nearly unrecognizable. Even conventional sonar, which identifies items on and beneath the seafloor using sound waves, has difficulty discerning UXO from rocks or scrap of similar shape.
To gain insights into how to recognize these elusive dangers, Hodges’ team examined AN-Mk 23 practice bombs retrieved from a pond on Martha’s Vineyard. Submerged for 80 years, these artifacts provided valuable information about how corrosion changes both the visual appearance and acoustic characteristics of underwater munitions.
How Acoustics Is Transforming the Field
The innovation resides in a method called acoustic scattering. Instead of merely reflecting sound waves off an object and measuring the returning signal (as with typical sonar), acoustic scattering investigates how sound waves interact externally and internally with submerged items.
This methodology offers a unique benefit: it essentially enables researchers to “look inside” the target or spot objects buried beneath sediment. As Hodges explained, “Acoustic scattering techniques provide insight into the internal structure of the imaged object, as well as a means to ‘see’ into the seafloor.”
Notable findings from their investigations include:
– Severely corroded munitions produce weaker sound signals, complicating detection through conventional methods.
– The resonance patterns—the vibration response of objects to sound—alter as the material deteriorates.
– Corrosion modifies the dimensions and form of the weapons, creating acoustic signatures that diverge from established templates.
– These modified signals can mislead current detection systems, resulting in overlooked or miscategorized threats.
Restoring Safety to Former Hazard Zones
The ramifications of this research are profound. As former military locations shift to public utility, understanding the risks presented by concealed munitions is vital for safeguarding public well-being. A misstep on a beach or an inquisitive dive in shallow waters might result in injury or fatality from an unexpected explosion or exposure to hazardous substances leaking from old explosives.
There are ecological concerns as well. As munitions corrode, they not only become mechanically unstable but can also contaminate the surrounding environment. Metals and chemicals from the explosive materials may seep into water supplies or affect marine ecosystems already strained from climate change and overfishing.
Hodges’ team is persistently refining their methodologies, broadening their studies to encompass various types of ordnance from different settings. Their ultimate aim: to create a database of acoustic signatures that enables rapid, accurate, and cost-effective identification of concealed submerged threats.
Looking Toward the Future: Saving Lives with Sound
One of the most encouraging aspects of acoustic technology is its cost-effectiveness and scalability. Unlike underwater excavation or manned inspections, sonar-based acoustic mapping can be swiftly deployed over extensive areas, providing a proactive approach to managing UXO cleanup.
As Hodges remarked, “Finding and recovering underwater UXO can be challenging, so it’s crucial that this is conducted safely and effectively. We