Passive Acoustic Monitoring: Listening for marine life

Passive Acoustic Monitoring (PAM) in this context basically means making audio recordings underwater, preferably:

  • year-round if not for several years

  • 24/7, night and day

  • covering the highest frequencies possible  

  • and the full dynamic range from silence to the loudest signals

As one can imagine, running a tape recorder continuously for years in a row is energetically quite demanding, even more so, when you would like to do so in a remote ocean during long periods of darkness during wintertime.  Fortunately, starting with the invention of the CD technology, progress in digital recording and storage now allow to acquire battery powered autonomous passive acoustic recorders that can continuously collect high-end underwater recordings.

We have been and continue such recorders in two different ways:

  • buried, since 2006,  in the floating shelf ice with a hydrophone dangling from the bottom of the ice shelf, baptized PALAOA (Perennial Acoustic Observatory in the Antarctic Ocean, or “whale” in Hawaiian.

  • attached, since 2008, to deep-sea mooring of the oceanographic Hybrid Antarctic Float Observatory (HAFOS), which are distributed across the Weddell Sea.

See the figure for a map of the recording sites covered so far.  Please note that not all sites are equipped with recorders all the time.

Map of sites of underwater acoustic recordings collected by AWI Ocean Acoustics group since 2006.

The old PALAOA station (foto)


Since December 2014 PALAOA consists of a simple box contained the very same acoustic recording unit as the recorders used by HAFOS and 2 simple car batteries for power.  This takes advantage of the recorder sitting just under the icy surface of the ice shelf and being regularly accessed by the Neumayer overwintering team every few months for battery replacement and data retrieval.  PALAOA now records year-round, 24/7 at a 98000 Hz sampling rate with 24-bit depth, saving wav files of 10-min lengths

Before (2006 –2014) PALAOA actually featured an entire alternative energy solution (batteries, solar, wind and fuel cell) to power real-time data transmission from PALAOA to Neumayer station, collecting data from two hydrophones using lab-type digitizing equipment.  Data was recorded year-round, 24/7 at a ….Hz sampling rate with …bit depth, saving 1-minute long compresses mp3 files which were broadcasted to the internet.


The current PALAOA Box at.... during maintenence by Neumayer and OZA teams. 


A HAFOS deep-sea mooring consist of a several thousand meters long rope extending from the sea floor, where it is attached to an anchor weight, to some 200m below the sea surface, where it is attached to floatation elements that keep it upright throughout the water column.  Distributed along this rope, one or more acoustic recorders, along with other oceanographic instrumentation are attached.  Moorings are deployed by ship – primarily our beloved RV Polarstern – and recovered 2-3 years later.  Only then we are able to download the data and learn what surprised might be buried therein.  Early recorders covered up to 11 months at 5553 Hz, 24-bit depth, while latest versions cover up to 24 months at 48000 Hz, the improvement mostly being due to increases in SD card memory sizes.

Sketch or image of HAFOS mooring


The AWIs FRAM (Frontiers in Arctic Marine Science) moorings also hosts a set of underwater recorders   northern Greenland Sea. Together with so called AZFPs ( Acoustic Zooplankton and Fish Profiler) the monitor for whales, seals, fish and invertebrates between Spitsbergen and Greenland. 

MAP of FRAM moorings

OPUS: The Open Portal to Underwater Soundscapes

To share these underwater soundscapes with you, we are in the process of creating OPUS, the Open Portal to Underwater Soundscapes.  The portal will give access to HAFOS, FRAM and PALAOA recordings by audio and synchronized spectral visualizations at staggered temporal resolution.  Just klick this link, select an recorder and enjoy underwater (night-)life. 

Picture shows a SonoVault in one of our moorings

Dedicated field studies

Over the years we also conducted some dedicated field studies, limited in scope and duration, to address specific questions like ....

2019  eDNA-PAM pilot Port Elizabeth, SA

Pilot study by HIFMB-AWI off Port Elizabeth (South Africa) during which passive acoustic records and water samples for eDNA were simultaneously collected, this approach will allow direct comparison of species detections between both methods.

2014/15 Acoustic mensuration of RV Polarstern during expedition PS89   (

To capture the sound field of RV Polarstern as experienced by a marine mammal close to the sea surface we recorded the ship's passage on two occastions with hydrophones dipped to 10m depth from a free drifting zodiac while RV Polarstern passed by at 10kns  (Closest Point of Approach, CPA ca. 180m)

2013 Acoustic mensuration of cargo ship Nadezhda

To capture the sound emission of a fully powered POD drive, we conducted an acoustic mensuration of cargo ship Nadezhda while steaming.  Recordings were taken using a bottom mounted icListen hydrophone and Reson TC4032 lowered from pilot vessle Döse.

2010/11 Polarstern expedition ANT-XXVII/2   (

Field Recordings at Rothera

2009 Polarstern expedition ANT-XXV/2   (

Deployment of 6 GPS tracked PALAOA-S recorders near Maud Rise.  RESON TC4032 hydrophone connected to an M-Audio recorder. with solar panel.

2008 Polarstern expedition ANT-XXIV/3   (doi:10.2312/BzPM_0606_2010)

Deployment of 2 PALAOA-S recorders in Atka Bay.  RESON TC4032 hydrophone connected to an M-Audio recorder in Zarges box.

2005 Polarstern expedition ANT-XXII/3   (doi: 10.2312/BzPM_0533_2006)

Test of an passive acoustic streamer towed behind Polarstern, deployment of 10 sonobuoys, deployment of 3 PODs in Weddell Sea.

2003 Polarstern expedition ARK XIX/4  (

Stationary acoustic mensuration of RV Polarstern and its hydroacoustic equippment at the Heggerness acoustic range in the Herdle Fjord, Norway.  Acoustic measurements were counducted by the Wehrtechnische Dienststelle WTD71, who operated the range together with its European partners.

2002/3 Polarstern expedition ANT-XX/2

First trials of underwater recordings in Atka Bay.

Additional:  - PASATA  -  PALAOA Satellite Recorders  -  Doggerbank Recordings

PASATA foto?