As Denmark considers deploying thousands of drone detection sensors across privately owned properties, passive acoustic technology could play a central role in protecting critical infrastructure without requiring large or intrusive installations.

Ukraine has demonstrated how thousands of relatively simple acoustic sensors can form an extensive early-warning network against drones. Its Sky Fortress system shows that effective aerial surveillance does not necessarily depend on large radar installations or expensive individual systems. Instead, a distributed network of smaller sensors can provide valuable detection and tracking information across vast geographical areas.

Now, Denmark is considering how a similar principle of distributed detection could strengthen national security. Rather than relying exclusively on individual radar installations and isolated surveillance systems, the country is exploring the framework for a connected network of sensors across a much wider geographical area.

A distributed solution

Airports, energy facilities, ports, telecommunications infrastructure and water utilities all face growing challenges from unauthorised drone activity. Detecting potential threats early is essential to maintaining operational security and enabling an appropriate response. Traditional surveillance technologies, including radar and optical cameras, remain important components of modern counter-drone systems. However, no single technology can provide perfect capabilities under every operational and environmental condition.

Radar performance may be challenged by terrain and surrounding structures, while cameras depend on visibility, lighting and an unobstructed view of the target. Passive acoustic sensors provide a complementary layer of detection by listening for the characteristic sounds generated by drone motors and propellers.

Unlike active radar systems, acoustic sensors do not need to transmit signals to detect an object. Instead, they abosrb and analyse sound present in the environment, identifying acoustic signatures that can indicate the presence, type and direction of a drone. This makes acoustic detection particularly relevant as part of a wider, multi-layered surveillance architecture.

Denmark prepares for a nationwide drone detection network

On 10 November 2026, Danish technology publication ResilienceTech, part of the Ingeniøren media group, reported on proposed legislation that would allow the Danish Defence to install drone detection systems on privately owned properties.

According to the article, “Forsvaret vil installere sensorer på privat grund: Virksomheder frygter ekstraregning” (The Danish Defence Wants to Install Sensors on Private Property: Businesses Fear Additional Costs), the ambition is to create a nationwide network capable of detecting, identifying, and tracking drones. The Danish Ministry of Defence has indicated that the installations would typically consist of small, passive sensors distributed throughout the country.

The proposal raises important questions concerning rights, compensation, responsibility, and the potential security implications of installing military equipment on civilian infrastructure.

Industry organisations representing energy, water and wastewater utilities have raised concerns about the potential costs of additional security measures, particularly where installations could increase the risk of sabotage or affect the operation of critical facilities. However, the debate also highlights an important technical question: How can Denmark establish a comprehensive drone detection network while keeping the impact of individual sensor installations as limited as possible? Passive acoustic technology offers one part of the answer.

Demonstrated during NATO SET-348

The importance of integrating different detection technologies was also highlighted by the Danish Ministry of Defence Acquisition and Logistics Organisation (FMI) in its article “Når dronerne nærmer sig, skal teknologien kunne svare igen” (When Drones Approach, Technology Must Be Able to Respond), published on 10 November 2026. The article describes NATO SET-348, a research activity under NATO's Science and Technology Organisation, focused on improving the detection of small drones in complex environments.

Hosted in Jægerspris, Denmark, the activity brought together companies, researchers, and defence stakeholders to explore how different technologies could contribute to effective counter-drone capabilities.

One of the central highlight from FMI is that individual sensor technologies are rarely sufficient on their own. Acoustic sensors, radar, cameras, and command systems (C2) must be able to exchange information and contribute to a shared operational picture. This principle was demonstrated by BSS during the week-long NATO SET-348 demonstration mentioned in FMI's article.

BSS deployed its Komodo passive acoustic counter-UAS system alongside solutions provided by Circle Scope and the Danish Defence. The demonstration combined Komodo's acoustic detection capabilities with Circle Scope's electro-optical and infrared (EO/IR) cameras and command-and-control platform, while the Danish Defence contributed radar surveillance.

When Komodo detected, classified and localised a drone, its position data was transferred to the integrated system, enabling Circle Scope's cameras to automatically acquire and track the designated target for visual or thermal verification. This integration showed how acoustic detection can support the transition from an initial warning to a more informed assessment of an airborne object.

The demonstration did not establish a nationwide surveillance capability. It did, however, provide a concrete example of how acoustic sensors can contribute to a multi-layered counter-drone architecture. And for Denmark, this is a relevant technological building block.

Read more about the NATO SET-348 demonstration in BSS' article The Sensor Consensus from June 26, 2026.