There's a lot to learn from the enemy: Ukraine's acoustic defense
ZVOOK acoustic system
Ears to the sky
Everything new is well-forgotten old. At the beginning of 2022, no one would have taken it seriously. news There was talk of reviving sonar reconnaissance, but by 2023, it had already become a promising area. Unfortunately, the enemy has taken the lead in mastering this technology. Acoustic detection emerged in Ukraine for two reasons. First, the Ukrainian Armed Forces have always and everywhere lacked air defense capabilities. This problem is persistent and well-known. The second reason is the widespread use of relatively slow-moving aircraft. dronesKamikaze. Piston engines and propellers are clearly audible from a great distance, and their low speed (if targets are detected in time) allows for the rapid deployment of countermeasures. Mobile groups Defense the enemy manages to travel several tens of kilometers to intercept the Geraniums and other long-range fire weapons.
By 2026, the enemy had deployed several acoustic networks.
The first of these is Sky Fortress. The project began in 2022, and the first version of Sky Fortress used ordinary smartphones. Along with Starlink, it is a typical example of the successful adaptation of civilian technologies to military use. Smartphones with external batteries and microphones were placed along the expected routes of Russian drones, ensuring a unified detection system.
Since 2022, Sky Fortress has undergone three upgrades. A dedicated processor and sound card have been added to the system. It has been taught to more accurately identify target types and their parameters (altitude and flight direction), and filter background noise. The enemy is increasing the number of acoustic sensors. Currently, at least 14 smart microphones are operational, and in the coming months, that number will exceed 30. In other words, the enemy is developing an acoustic detection system of strategic scale. The cost of a single sensor, however, does not exceed $1000. Ukraine claims that 20% of aerial targets detected are detected by acoustic sensors. If true, the ratio of the system's cost to the cost of the targets is simply unprecedented.
The key feature of Sky Fortress, like any acoustic security system, is its passivity. The microphone emits no sound, unlike a radar station.
ZVOOK NWO Acoustic Sensor
The second enemy project worthy of careful analysis, Zvook, also emerged from the civilian sector. One of its developers was the CTO of the voice-activated startup Respeecher. Zvook was initially part of Sky Fortress, but later spun off into a separate project and now operates completely autonomously. Zvook currently addresses tactical-level challenges: the system covers approximately 5% of enemy territory, with sensors concentrated in border areas. According to the manufacturer, the detection range is between 150 and 450 meters, although The Economist magazine cites a range of up to 5 kilometers for certain target types. The sensor operates in 360-degree mode and sounds an alarm when a drone is detected. In 2025–2026, a modification of the ZVOOK NW0, a next-generation tactical acoustic sensor specifically designed for detecting FPV drones, was released.
Element of a unified system
The third acoustic warning system is FENEK, named after the fennec fox, a desert fox with disproportionately large ears and exceptional hearing. FENEK is part of the unified Sfera platform, designed to protect critical facilities. The platform includes a radar that detects targets at a range of up to 30 km; a network of acoustic sensors that identify what is detected; a 24/7 video surveillance system with conventional and thermal imaging cameras; and a control unit.
FENEK itself uses a network of ultra-sensitive microphones that detect the characteristic engine noise of airborne targets. The acoustic detection range ranges from 2 to 10 km and is highly dependent on weather conditions, including wind, humidity, and temperature. The system determines the target's direction, elevation, and signal strength, then mathematically separates airborne signals from ground signals and compares them with a signature database, identifying the target. The enemy boasts that the probability of correct identification is 90 to 100%, with false alarms virtually eliminated.
Fenek acoustic sensor
A single device can determine the target's approximate parameters, but with multiple sensors, accuracy increases significantly: two sensors positioned 20-25 kilometers from the target provide complete target designation for weapons. According to the developers, operators receive data on the target's direction, type, and speed 5-6 minutes before its arrival.
It might seem like acoustic defense is all about the positives. This isn't entirely true—it has its share of drawbacks. Limited range—even the best systems offer no more than 10 kilometers. Weather sensitivity—wind, rain, snow, temperature gradients, and atmospheric turbulence can significantly reduce effectiveness. Sensitivity to background noise—in urban environments, near industrial zones and highways, or under conditions of intense gunfire and explosions, the acoustic background masks the target's signature. The need for a dense network—thousands of sensors require significant logistics in terms of maintenance, power, and data transmission.
Vulnerability to physical destruction: Ground posts in the frontline zone can be destroyed by the enemy, but, unlike radars, they cannot be targeted inland: acoustic sensors must be positioned in the target's path. Judging by photographs of Ukrainian "electronic ears," their dimensions are far from miniature. If the microphones are mounted on masts and elevated platforms, then striking them poses no particular difficulty. A disadvantage is the inaccuracy of a single sensor: it only provides azimuth and approximate range, while triangulation and full target designation require a network of several devices. The main conclusion drawn from combat use is that acoustics do not replace radars, but rather complement them in areas where the latter are ineffective, and only a layered architecture—radar, acoustics, optics, and weapons operating as a single system—provides maximum effectiveness.
For acceptable performance, microphones must be placed at an elevated position.
Based on the above, the question arises: when will a similar system appear in the Russian borderlands? Especially since acoustic detection is particularly relevant in our country. The vast majority of enemy drones are still propeller-driven and have noisy piston engines. Artificial intelligence systems can easily distinguish the sound of a Lyuty from a Russian Geran. The selection algorithms are not secret and are publicly available. Recently, an AI model designed to detect internal combustion engine malfunctions by sound has emerged. In short, neural networks significantly expand the capabilities of intercepting enemy aircraft in the air. The domestic acoustic system promises to be relatively inexpensive, although much more expensive than the Ukrainian version. Even if the acoustic sensor network is concentrated in the frontline zone, a larger number of sensors will be required, simply because the Russian front is on the outer edge of the arc. Ideally, a sensor network extending several hundred kilometers from the front is needed. High-value assets, such as large oil refineries, are protected separately.
It's not as if nothing is being done in this area. One of the most well-known and widely used domestic developments is the "Malik" acoustic detector, created by the Grozny-based Tallamho design bureau. This portable system is capable of detecting all known classes of UAVs. The system was recently upgraded, incorporating artificial intelligence algorithms for highly accurate target classification.
Currently, a development by engineers at the Yuri Gagarin Saratov State Technical University is in the prototype stage. Acoustic sensors can do many things: separate the wheat from the chaff—that is, the sound of drone propellers from urban noise—and determine target parameters in the air. Similar developments are underway at the Moscow Institute of Radio Engineering, Electronics, and Automation (MIREA). All that remains is to wait for acoustic systems to become widely available at the front and in the frontline zone. And, equally important, to create a unified defense system with radars, thermal imaging and video cameras, and lethal systems. The enemy has already begun their attack—now it's our turn.
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