Swedish Defence Research Agency


Underwater Technology

In the field of underwater research, FOI is working on the development of marine reconnaissance and surveillance systems that, among other things, can be used both for countering threats and the prevention of criminal activity.

Experiment in tanklaboratory in Kista

The scope of the research has now been widened from strictly military applications such as submarine hunting, port surveillance and protection against mines, to include a whole range of civil applications, for example oil prospecting, pipeline inspection or the investigation of the effects of noise in the underwater environment. By combining different research methods in the form of simulation and modelling, signal processing and analysis with experimental research, FOI has created a unique body of competence in such areas as the underwater environment, acoustics and electro­magnetics. Because of Sweden’s position in the Baltic we have long experience of working in shallow water and the special conditions that exist there.

The research is funded largely through assignments received from the Swedish Armed Forces, the Swedish Defence Materiel Administration, govern­ment ministries and Swedish industry, but work is also carried out for civil research bodies and a variety of overseas customers. A certain amount of the research work is conducted in the form of collabo­ration with universities, colleges and other research institutions both nationally and internationally.

Competence Areas

Acustic experiment

The purpose of the research in this area is to understand and to be able to describe the propagation of sound waves in air, water and in solids. The centre of gravity of the research lies in the area of hydro acoustics and includes, for example, work for the Swedish Armed Forces on the develop­ment of reconnaissance systems and methods for submarine hunting, port protection, mine clearance and under­water communi­cation. The advanced models developed in the course of this underwater research can also be applied to sound propagation in air from various types of noise sources, for example explosions and wind generators. The understanding of sound propagation in solid materials can be applied to the reduction of submarine acoustic signatures, seismic prospect­ing technology and the classification of buried objects.

electromagnetic experiment

Research in this area is directed towards understanding and being able to describe the propagation of electric and magnetic fields in the sea and on the sea bed. One important activity is to measure and model the electro­magnetic environment in the water column to enable, for example, the Swedish Armed Forces to calculate ranges for sensors and ship signatures. Other applications include determining, when charting the sea bed, the electrical properties of the sea bed and the underlying bedrock, e.g. in support of prospecting.

Underwater enviremental experiment

The purpose of FOI’s research in this area is to investigate how sound affects marine life. One primary line of research involves the measure­ment and modulation of sound pressure and particle motion in the water and then studying the effects. FOI carries out assignments for both civil and military customers. The research is conducted in close collaboration with a number of universities and FOI is a participant in numerous international cooperation arrange­ments. These include the Helsinki Commission (HELCOM) and the OSPAR Convention.

Research Methods

Collage of research pictures


In order to protect Swedish waters and coasts, new experimental methods and systems are being developed for the recording of acoustic and electro­magnetic signals. These signals may originate from either surface shipping or underwater vessels, as well as from divers or marine life. The systems may be stationary, for example when taking measurements over prolonged periods, or they may be mobile and therefore capable of covering large areas, for example systems designed for auto­nomous craft. Results of the experi­mental research are also applicable to areas such as prospecting and oceanography. 

Signal processing / Analysis 

In order to extract information from signals recorded by the experimental systems, the signals must be represented, manipulated and transformed by means of various signal processing algorithms. Developments in the field of computer technology mean that ever more advanced signal processing algorithms can be used, which in turn means that existing systems can be improved and given new capabilities. Signal processing is also employed to make reconnaissance systems more robust by making them more resistant to various naturally occurring or deliberate forms of interference.

Simulation / Modelling

The development of new sensor systems continues and it is possible to simulate and model signal propagation in the environment where the sensors are designed to operate. Typical Baltic Sea environments are often compli­cated due to the shallow depth and the many skerries, islands and islets in the coastal waters. The research covers the development of software for acoustic, elastic, and electro­magnetic wave propagation. An important component of this work is to understand the source and this involves advanced signature calculations which in many cases may have to take specific account of the environment concerned. The propa­gation of these waves towards various targets, for example submarines, divers and buried mines, is also modelled using the tools we are developing. Simulation and modelling is also a cost-effective way of assessing the performance and effectiveness of the design of new underwater systems, which is very useful, for example for the Swedish Armed Forces in equipment modernisation and the procurement of new materiel.


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Last updated: 2020-12-21