As drones become a daily threat, Ukraine has been laying down “very cheap acoustic sensors” that listen for low-flying aircraft. NATO, the EU and Baltic countries are now looking to replicate parts of the model—because traditional air defense networks were bui
In Ukraine’s air defense network, the microphone matters.
Defense officials in the West are being told to stop treating sensors as a luxury for high-tech militaries and start treating them as a scale problem—especially at low altitude, where drones slip in differently than jets and missiles.
Sir John Stringer. NATO’s Deputy Supreme Allied Commander Europe. said the West needs to “get back to investing in the range of sensors that we need.” For defensive air defense purposes. he said. that includes “very cheap acoustic sensors”—microphone-based systems that listen for drones. He also described seeing that approach implemented in Ukraine alongside more advanced sensors.
The Russian full-scale invasion has turned drones into a daily battlefield threat, and that has exposed capability gaps. Drones fly low and behave unlike crewed aircraft and missiles, which means older detection assumptions don’t always hold.
Maj. Modris Kairišs. the head of Latvia’s Autonomous Systems Competence Center. a drone-warfare testing and training hub. told Business Insider that the West needs “to rebuild our system. put a lot of additional sensors for detecting things at low altitude because these drones are flying very low.” He said traditional air defense systems were primarily built around aircraft and missiles that fly higher and faster. creating “issues with detection.”.
Kairišs stressed that variety matters as much as quantity because “every sensor has strong and weak points.” The practical lesson is that cheap sensors don’t replace high-end systems; they fill in where those systems struggle.
He also argued that Western militaries may not need to start from scratch. The bigger issue, he said, is buying and fielding equipment faster.
That speed question sits inside a wider argument from air defense experts: effective coverage is not a single invention—it is a network.
Justin Bronk. a top airpower expert at the UK-based Royal United Services Institute think tank. previously told Business Insider that air defense is “hugely complicated and requires linking together lots and lots of different types of sensors” to cover different areas. altitudes. and threat speeds. He said an effective air defense network “requires you to layer multiple types of air and missile defense systems around an object or area that you want to protect. ” ranging from expensive. high-end interceptors to cheaper systems designed with drones in mind.
Ukraine’s approach centers on cheap detection to buy time for response. The country is using cheap sensor networks. including acoustic sensors that listen for incoming drones and cost far less than military radars. Those sensors form part of a wider air defense system that includes expensive. high-end equipment. helping Ukraine spot low-cost drones early enough to respond.
Western officials are trying to copy that logic.
Lt. Gen. Sean Gainey, then the commander of US Army Space and Missile Defense Command, said in 2024 that the US ought to integrate the kind of low-cost acoustic sensors that Ukraine has into its network.
And Tom Goffus, then NATO’s assistant secretary general for operations, said last year that “essentially, Ukraine is covering its entire nation, 1,000 meters and below,” with acoustic sensors for less than $54 million.
The attraction is not just technical—it is financial.
Andrius Kubilius. the European Union’s defense commissioner. warned last year that the West does not have “the capability” to detect drones. or only has a limited one. “Our radars see aircraft. they see missiles. but they do not see very precisely drones that fly very. very low.” He said plans for a European drone wall—a proposed network of sensors and defenses against drones—should emulate Ukraine’s capabilities. including thousands of sensors.
Baltic countries, NATO members that border Russia, have announced or moved toward buying acoustic sensor systems, explicitly citing lessons from Ukraine.
But the push for new sensors is running alongside a harder realization: the kinds of air dominance Western militaries achieved in some recent conflicts may be harder to secure in future wars. Stringer said it remains necessary to keep aiming for that foundation. “You still need to secure air superiority. The ways of doing it may change, but it fundamentally provides a foundation on which the entire joint force operates. So if you’re not able to secure the access and then the maneuver that you force needs. then you’re failing.”.
What changes is how you fight for it.
Stringer said the West’s air defense response needs to be “on the right part of what we call the cost curve”—using defenses that are not wildly more expensive than the threats they are meant to stop. He cited a clear example of doing it wrong: using multimillion-dollar interceptors against far cheaper drone threats.
He pointed to Iranian-designed Shahed one-way attack drones, versions of which Russia also makes, with estimated costs of $20,000 to $50,000 each. In contrast, US-made Patriot Advanced Capability-3 (PAC-3) interceptors are estimated to cost roughly $3.7 million each. Stringer said that math is “unsustainable” in a long air war.
A network built for drones isn’t just about what it can detect. It is about how long it can afford to keep doing it.
As aerial threats have multiplied, cost matters because cheaper sensors let militaries cover more airspace. Ukraine’s experience also reinforces a practical lesson that modern war can burn through equipment quickly—meaning Western countries may need larger stocks of cheaper systems alongside advanced gear.
In the end. the Western shift toward acoustic sensing is less about chasing novelty than about resisting the economic trap of mismatched costs. If drones keep arriving low and in numbers. air defense will have to look less like a high-end showroom and more like a distributed system—layered. faster to field. and designed to keep operating when the threat is cheap enough to overwhelm expensive responses.
Ukraine air defense acoustic sensors drones NATO Latvia Autonomous Systems Competence Center European drone wall Shahed drones PAC-3 interceptors cost curve low altitude detection Sean Gainey Tom Goffus Andrius Kubilius Sir John Stringer