Archival Marine Acoustic Recording Units (ARUs)

Image of a archival marine acoustic recording unit.

A “pop-up” listening device (archival marine acoustic recording unit) being deployed off the coast of Massachusetts. This autonomous recording unit continuously listens for and records ocean sounds. Image Credit: Denise Risch, NEFSC/NOAA.

The use of passive acoustic monitoring (PAM) has increased with the availability of relatively inexpensive devices to record large amounts of acoustic data on marine animals. One type of passive acoustic sensor is the archival marine acoustic recording unit (ARU). Archival refers to data that are collected and stored by the unit for analysis after the instrument is recovered.

Many different ARU systems have been developed to detect and record the sounds of vocalizing marine animals, providing information on the distribution of these animals, including those that are otherwise difficult to study. The recording packages vary widely in their size, configuration, and length of deployment. Several can be deployed together, as an array, to make it possible to detect, localize, and track vocalizing marine mammals or fishes. ARUs can be deployed in remote and/or extreme locations, such as ice-covered polar regions, and can be incorporated into ocean gliders.

An understanding of the acoustics and behavioral ecology of each species in question is needed to effectively interpret and apply ARU data.  Without an understanding of a species’ acoustic repertoire, calling behavior, and/or seasonal and geographical variations in call usage, no clear scientific or management question can be resolved.

Scientific and management questions are being addressed by integrating passive acoustic data from multiple instruments.  These networks include the U.S. NorthEast Passive Acoustic sensing Network (NEPAN; and the NOAA/NPS Ocean Noise Reference Station Network (

Additional Links on DOSITS

Additional Resources


  • Fox, C. G., Matsumoto, H., & Lau, T.-K. A. (2001). Monitoring Pacific Ocean seismicity from an autonomous hydrophone array. Journal of Geophysical Research: Solid Earth, 106(B3), 4183–4206.
  • Hanson, M. B., Emmons, C. K., Ward, E. J., Nystuen, J. A., & Lammers, M. O. (2013). Assessing the coastal occurrence of endangered killer whales using autonomous passive acoustic recorders. The Journal of the Acoustical Society of America, 134(5), 3486–3495.
  • Koschinski, S., Diederichs, A., & Amundin, M. (2008). Click train patterns of free-ranging harbour porpoises acquired using T-PODS may be useful as indicators of their behavior. Journal of Cetacean Research Management, 10, 147–155.
  • Mann, D. A. (2012). Remote sensing of fish using passive acoustic monitoring. Acoustics Today, 8(3), 8.
  • McDonald, M. A., Hildebrand, J. A., Wiggins, S. M., Johnston, D. W., & Polovina, J. J. (2009). An acoustic survey of beaked whales at Cross Seamount near Hawaii. The Journal of the Acoustical Society of America, 125(2), 624–627.
  • Mellinger, D., Stafford, K., Moore, S., Dziak, R., & Matsumoto, H. (2007). An overview of fixed passive acoustic observation methods for cetaceans. Oceanography, 20(4), 36–45.
  • Moore, S. E., Stafford, K. M., Mellinger, D. K., & Hildebrand, J. A. (2006). Listening for large whales in the offshore waters of Alaska. BioScience, 56(1), 49.[0049:LFLWIT]2.0.CO;2
  • Munger, L. M., Wiggins, S. M., Moore, S. E., & Hildebrand, J. A. (2008). North Pacific right whale ( Eubalaena japonica ) seasonal and diel calling patterns from long-term acoustic recordings in the southeastern Bering Sea, 2000-2006. Marine Mammal Science.
  • Sousa-Lima, R. (2009). A review of fixed passive acoustic monitoring systems. Presented at the Workshop on the Status and Applications of Acoustic Mitigation and Monitoring Systems for Marine Mammals, Boston, MA.
  • Sousa-Lima, R. S., Fernandes, D. P., Norris, T. F., & Oswald, J. N. (2013). A review and inventory of fixed autonomous recorders for passive acoustic monitoring of marine mammals: 2013 state-of-the-industry (pp. 1–9). IEEE.
  • Thomas, L., & Marques, T. A. (2012). Passive acoustic monitoring for estimating animal density. Acoustics Today, 8(3), 35.
  • Van Parijs, S., Clark, C., Sousa-Lima, R., Parks, S., Rankin, S., Risch, D., & Van Opzeeland, I. (2009). Management and research applications of real-time and archival passive acoustic sensors over varying temporal and spatial scales. Marine Ecology Progress Series, 395, 21–36.
  • Wiggins, S. (2003). Autonomous acoustic recording packages (ARPs) for long-term monitoring of whale sounds. Marine Technology Society Journal, 37(2), 13–22.
  • Wiggins, S. M., & Hildebrand, J. A. (2007). High-frequency Acoustic Recording Package (HARP) for broad-band, long-term marine mammal monitoring. In 2007 Symposium on Underwater Technology and Workshop on Scientific Use of Submarine Cables and Related Technologies (pp. 551–557). IEEE.