Kongsberg’s Listen is a passive electromagnetic sensor system designed for measuring electric and magnetic fields in seawater and optimized for integration on HUGIN AUVs. When installed on HUGIN, Listen uses hull‑flush‑mounted electrodes arranged into eight electrode pairs to reconstruct the full three‑dimensional electric field, combined with magnetometers that provide complementary magnetic measurements. This configuration enables low‑noise, repeatable data acquisition well suited to long‑range AUV missions.

Listen supports contactless cathodic protection (CP) inspection by exploiting the electric fields generated by active CP systems. A HUGIN AUV equipped with Listen can survey pipelines at typical altitudes of 5–10 m and speeds of 3–4 knots, continuously measuring the 3D electric field without physical contact. From these measurements, anode output currents, return currents into the structure, and anode material consumption rates can be estimated, enabling assessment of CP performance, coating condition, and remaining lifetime. The electromagnetic data can be integrated with navigation, camera, and multibeam echosounder data to deliver decision‑ready integrity information with high productivity and reduced operational risk.

Beyond CP inspection, Listen enables buried power cable detection, positioning, and burial‑depth estimation. Sea trials with the Listen receiver system deployed on a Hugin Superior AUV demonstrated high signal‑to‑noise electric and magnetic field measurements at the 50 Hz powerline frequency across multiple passes and altitudes. The results showed reliable cable detection at altitudes up to 20 m and burial‑depth estimation using combined electric‑ and magnetic‑field analysis, highlighting the value of multi‑field sensing compared to magnetic‑only approaches.