The International Quiet Ocean Experiment (IQOE) was an international scientific program to promote research, observations, and modelling to improve understanding of ocean soundscapes and effects of sound on marine organisms.
Project Rationale
The ocean has always been a noisy place. Before humans began intensive use of the ocean, sound in the ocean resulted from physical processes such as the breaking of waves, wind blowing across the surface, lightning strikes, ice cracking, and undersea earthquakes. Adding to this were biological sources of sound, from the sound of snapping shrimp and fish such as croakers, to the high-frequency vocalizations of toothed whales (e.g., dolphins, killer whales, and sperm whales) and low-frequency calls of baleen whales such as blue and humpback whales.
In the past several hundred years, human activities have altered the sound field in the ocean. Large-scale whaling and fishing of noise-producing species reduced sources of biological sound to the ocean. As industrial activities moved into the ocean, such as motorized ships, oil expoloration and extraction, and pile driving, this added new human-generated sound to the ocean. Sonar, developed and perfected in World War II, made it possible to locate submarines in the ocean by reflecting sound off them. Some oceanographers used sound to study various aspects of the ocean.
Sound has increased in the ocean over time, leading to an interest by many scientists in studying how this might be affect organisms in the ocean. Many individual scientists and small research groups have studied ocean sound and its effects on organisms for the past 60 years, but there has never been a large-scale international project of coordinated research. The scientific community believes that it is important to bring together scientists who study sound in the ocean and those who study its effects in the context of such a study. Thus was born the International Quiet Ocean Experiment.
Status
IQOE’s term as a decadal project was completed on 31 December 2025. Since 2015, IQOE implemented its Science Plan (available here) developed from an open science meeting in 2012. IQOE successfully coordinated a variety of activities in ocean acoustics and bioacoustics through IQOE working groups on the use of acoustics to assess biodiversity, the importance of acoustic observations in the Arctic Ocean, standards for reporting ocean acoustic and bioacoustic data for IQOE, software for making acoustic observations comparable worldwide, and recommendations for implementation of an Ocean Sound Essential Ocean Variable for the Global Ocean Observing System. IQOE progress has been documented since June 2018 through IQOE Newsletters and since the beginning of the project through other products. IQOE identified 2020 as the Year of the Quiet Ocean because of evidence that ocean sound decreased because of decreases in human activities in the ocean due to the COVID-19 pandemic.
Next Steps
Although IQOE has completed its term, several activities begun by IQOE will continue to work independently or under a new structure. The IQOE Science Committee set up a committee to convene an open workshop to plan the next steps for continuing IQOE activities and for implementation of the Ocean Sound Essential Ocean Variable (EOV). The workshop will be held on 22-24 September 2026 at the Flanders Marine Institute in Oostende, Belgium. More details about the workshop will be forthcoming in the near future.