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Key technology against drones — back to acoustics
Acoustic technologies are once again becoming a key tool in countering modern drones, which have learned to evade radar and radio monitoring. By combining the physics of sound with artificial intelligence, these systems make it possible to detect low-visibility aerial targets in situations where other methods no longer work.
This was reported by Louis Saillans, founder of Askalon Industries and a retired officer of the French Navy, for a Novyny.LIVE column.
Acoustic systems are back in the game against 21st-century drones
The expert notes that today, we are effectively revisiting developments from the 1940s to address the challenges of the 2020s. However, this is not about the concrete "ears" on the Kent coast that once listened to the sky for bombers. It's about returning to the physics of sound—now enhanced with artificial intelligence.
According to the expert, drones have learned to evade radar and radio monitoring, but they cannot eliminate the noise of their own rotors. Thus, acoustics — once a "forgotten" technology — is becoming an important tool for protecting cities, critical infrastructure, and the front lines.
How old "Ears" got a new life
The expert explains that when people think of acoustic drone detection, many imagine huge sound mirrors that once searched the sky for enemy planes. Those systems were slow, passive, and heavily reliant on humans. The invention of radar instantly made them obsolete, and acoustic solutions disappeared from military arsenals for decades.
Back then, these systems had several natural limitations: short range, weather dependency, and significant human involvement. They were designed to detect large, loud targets — not small, low-visibility objects. Today, however, the compact size of drones and rapid technological development are bringing acoustics back into defense. Instead of massive structures, we now have mobile sensors that can be easily integrated into modern infrastructure.
This resurgence became particularly relevant with the rise of drones that completely changed the rules of the game.
Why modern drones are changing defense approaches
The defense technology expert points out that plastic FPV drones, small reconnaissance drones, and autonomous systems can be virtually invisible to radar and radio monitoring. They do not reflect signals, do not emit control frequencies, and operate through mobile networks or even fiber optics.
FPV drones fly without any radio signature, and autonomous routes require no radio communication at all. Add to this the legal restrictions on jamming in cities, and traditional detection methods lose effectiveness. Threats are increasing, while operational tools are decreasing. That is why the focus is shifting from "seeing" to "hearing."
Returning to the basics of physics
Louis Saillans emphasizes that the laws of physics remain unchanged. To lift off, a drone must move air masses, which creates sound. And that sound is unavoidable — regardless of the drone's shape, material, or communication method.
Even a small quadcopter has a unique acoustic "signature" — the rhythm of its rotor movement, that cannot be hidden. Radar can be fooled by body materials or shape, optics by camouflage, thermal imaging by shielding — but sound remains.
Acoustics has long been used by nature: bats, certain animals, and even humans rely on it in complex environments.
How modern acoustic systems work
The expert explains that a modern acoustic sensor is a compact device that:
- filters urban noise;
- classifies threats in real time;
- operates autonomously, without the internet;
- recognizes, for example, a DJI drone in fractions of a second and does not confuse it with household devices.
The system analyzes sound similarly to how a camera analyzes an image: it creates spectrograms, compares them to a trained model, and determines the type of target. Algorithms filter out wind noise, traffic, and urban echoes.
A network of multiple sensors can determine a drone's direction and speed, creating an acoustic map of the space. All processing is performed locally.
Why "low-tech" is becoming high-tech again
Louis Saillans notes that the return of acoustics is not about nostalgia. In his view, the reason is simple: drones have learned to bypass complex, high-tech systems. Sometimes the most effective solution is the smart use of simple principles.
According to him, effectiveness does not necessarily mean complexity. In cybersecurity, simple attacks often work; in defense, simple and scalable systems are effective. Acoustics is exactly that: passive, inexpensive, energy-efficient, and suitable for deployment across many points.
The expert emphasizes that this is not a step backward, but an adaptation of basic principles to meet new threats.
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