December 30, 2004 — Over the past decade, increasing scrutiny has been directed toward "anthropogenic" (or human-induced) sound in the oceans because it may interfere with the ability of marine mammals to hear important natural signals (which they rely on to communicate with one another, navigate, find food, and avoid predators).

Marine mammal strandings in close proximity to loud human sound sources, new generations of sub-finding sonar, the use of acoustic signals (i.e., seismic airguns) to explore oil and gas reserves, and increasing vessel traffic in some ocean areas have led many to question the effects of human sound on the marine environment. Surprisingly, however, very little is known about the prevalence and significance of possible effects, which range from no effect at all to temporary disruption and/or severe disorientation.

The complexity of how sound travels (or propagates) under water has proven challenging to scientists attempting to determine causal relationships between sound exposure and related consequences. While sound typically propagates farther in water than in air — variations in temperature, sea floor geography, ocean depth and sound frequency can dramatically affect how far sounds travel and their characteristics when received. The fact that many marine animals are highly mobile adds another layer of complexity. (Click on NOAA image to the right for a larger view of the basic components of a sound wave. Please credit “NOAA.”)

Moreover, natural underwater sounds (especially storm-tossed waves and many marine species' vocalizations) can also be quite loud and pervasive at times, raising questions about possible anthropogenic acoustic impacts given that some ocean creatures may be well-adapted to deal with loud sounds. Scientists have made some strides in measuring sound from both natural and artificial sources. However, how anthropogenic sound sources add to the overall background din (i.e., ambient noise) in various ocean areas is almost completely unknown.

Fortunately, NOAA (in cooperation with other government agencies, conservationists, researchers and industry) is striving to understand underwater anthropogenic sound and its possible effects. Experts in this field are also working to develop acoustic technologies to mitigate potential impacts on marine mammals and other ocean life.

NOAA’s Ocean Acoustics Program
NOAA is investigating many potential impacts of human sound on marine environments and working to improve ocean acoustic knowledge and management through a variety of activities. Specifically, the NOAA Fisheries Acoustics Program provides technical advice to support management decisions, is supporting research on the effects of both natural and anthropogenic sound sources on marine mammals, and is planning a global passive acoustic monitoring network in collaboration with various NOAA and academic partners.

• Consultations and Mitigation: NOAA’s Acoustic Program provides interpretation and advice to NOAA personnel working on technical matters related to acoustic impacts on marine animals in the context of permit authorizations and consultation. A key component of this includes identifying alternatives that permit important human activities in the ocean with the greatest possible reduction of impact on protected species. For example, NOAA Fisheries has played a central role in NOAA decisions on military sonar systems and seismic airguns used by the oil and gas industry and academic researchers.
• Acoustic Criteria and Related Research: NOAA Fisheries is currently involved in the development of science-based noise exposure criteria for determining the impacts of human noise on different marine mammal species. Unfortunately, hearing has only been studied in about 15 percent of marine mammal species and one species of marine turtle. Even less is known about potentially harmful effects of intense noise on marine mammal hearing and behavior. In collaboration with acoustic experts from the academic community, NOAA Fisheries is developing acoustic criteria using current knowledge and has developed a full research program to provide the information needed to improve them. Specific research questions NOAA Fisheries is addressing include developing novel techniques to rapidly measure hearing in marine mammals, measuring effects of discrete and repeated acoustic exposure on individual marine mammals, evaluating potential impacts on entire marine mammal populations, and considering the possible effects of acoustic exposure on fish and turtles. (Click on NOAA image above right for a larger view of the spectrogram depicting a blue whale call, this spectrogram (upper image) plots time (horizontal axis) versus frequency (vertical axis), with warm colors representing high acoustic intensity. Spectrograms are a means of visualizing the energy and pitch of a particular sound. Please credit “NOAA.”)
• Workshops, Symposiums and Outreach: The NOAA Fisheries Acoustics Program has hosted a number of technical workshops, international symposia and public outreach efforts on specific aspects of the marine noise issue (including passive acoustic monitoring, non-auditory effects of sound exposure, stranding events coincident with acoustic exercises, and the emerging issue of vessel sounds and marine mammals).

Recent events hosted by NOAA Fisheries include:

• Educational Lecture Series: Along with the Marine Mammal Commission and a number of partners from the scientific research and aquaria communities, NOAA recently completed a series of 14 public lectures to increase the nation’s knowledge about human noise and marine animals. This educational lecture series, entitled "Marine Animals and Human Noise," presented current scientific information about human sources and uses of sound in marine environments, the physics of sound and hearing, and relevant biological and behavioral factors. The lectures drew approximately 1,000 people and facilitated constructive dialogue and many new partnerships between NOAA, researchers, aquaria, marine labs and the concerned public. (Click on NOAA image above right for a larger view of NOAA 's Brandon Southall presenting at one of the Marine Animals and Human Noise educational lecture series events. Please credit “NOAA.”)
• International Symposium on Shipping Noise and Marine Mammals: In cooperation with other government and industry partners, NOAA hosted the 1st International Symposium on “Shipping Noise and Marine Mammals” in May 2004. Sounds from large vessels are one of the most prevalent and widespread contributors to ambient noise in some ocean areas. Unfortunately, however there has been no formal effort to assess its impacts and to engage the various industries in possible mitigation. The purpose of this symposium was to better understand this emerging issue and form new partnerships to help address this issue in the future. The meeting was attended by leading biologists, acousticians, maritime engineers, vessel owners and operators and various government agencies, who participated in panel discussions and provided different perspectives on large vessel sounds, as well as the current need, costs and benefits of reducing it.

While NOAA Fisheries continues to work toward understanding these often complex issues, much progress has been made in learning about the impact of noise on marine life,” said Bill Hogarth, the assistant administrator for NOAA Fisheries. “It is very important to both share this information with relevant public and private sector organizations and continue to educate and inform the general public.”


NOAA Research Activities

Presently, researchers know even less about overall ambient noise from both natural and human sound sources than they do about their possible effects on marine mammals. NOAA scientists are working to design and deploy a global network of passive acoustic monitoring stations to collect acoustic measurements and identify trends in various ocean areas. The deployment of sampling platforms and data analysis is expected to involve several NOAA offices (e.g., NOAA Ocean and Atmospheric Research and NOAA Environmental Satellites, Data and Information Service) and other partners involved in ocean-observing systems. This acoustic monitoring effort will be coordinated with other existing acoustic sampling activities and contribute to the development of a NOAA Global Observing System. (Click on NOAA image above right for a larger view of NOAA's potential/existing hydrophone sites. Please credit “NOAA.”)

The Acoustic Monitoring Project of the NOAA VENTS Program has already been performing continuous acoustic monitoring and recording since August 1991 using both the U.S. Navy’s Sound Surveillance System network and later autonomous hydrophones (underwater microphones). At first, researchers at the NOAA Pacific Marine Environmental Laboratory (Newport, Ore.) used the U.S. Navy's Sound Surveillance System to monitor sound in the north Pacific. In May 1996, monitoring was expanded to the eastern equatorial Pacific using moored hydrophones developed by PMEL to focus on underwater seismic activity. Subsequent deployments have included the Eastern Tropical Pacific, the Gulf of Alaska and the mid-Atlantic Ocean. The NOAA Office of Ocean Exploration has also explored ocean acoustic issues. (Click on NOAA image above right for a larger view of NOAA's potential/existing hydrophone sites. Please credit “NOAA.”)

Although many acoustic monitoring efforts were originally designed to study underwater earthquakes and volcanic activity, initial examination of the data indicated numerous marine mammal calls. The powerful combination of the Navy’s Sound Surveillance System network and the autonomous moored hydrophone data has enabled PMEL researchers to record distinctive low-frequency calls from baleen whales (i.e., mainly blue and fin whales) throughout the Pacific Ocean, and even identify regional differences in blue and fin whale vocalizations. The data also allowed NOAA researchers to locate vocal whales, information that PMEL then used to identify apparent seasonal shifts in whale distributions. Correlating these data with National Marine Mammal Laboratory’s (Seattle, Wash.) current field observations and their extensive historical database of species distributions may help answer critical population and stock management questions.

NOAA’s ocean acoustic programs have and will continue to be actively involved in resolving uncertainties surrounding the impacts of anthropogenic noise on the ocean environment and the marine species that dwell within it. In doing so, NOAA will be better able to manage protected marine mammal (and other ocean) species. NOAA’s ultimate goal is to identify and use a balanced approach to share the ocean with marine life, and to conserve and protect marine creatures for many years to come.

Relevant Web Sites
NOAA Research

NOAA Fisheries

NOAA Fisheries Office of Protected Resources

Overview of the NMFS Acoustics Program

NOAA Ocean Explorer: A Collection of Sounds from the Sea

PMEL Marine Mammal Sounds

Acoustic Monitoring Program: Sounds (examples)

Acoustic Monitoring Program: Underwater Acoustics Tutorial

Saturday Academy – "Sound in the Sea" is a hands-on experience with NOAA/OSU scientists

NOAA Office of Protected Resources: Sounds in the Ocean

NOAA Ocean Explorer: Gallery on Sounds in the Sea

NOAA SCIENTISTS TO KICK OFF NATIONWIDE LECTURE SERIES ON HUMAN NOISE IMPACT TO MARINE MAMMALS

NOAA SCIENTISTS CONTINUE NATIONWIDE LECTURE SERIES ON HUMAN NOISE IMPACT TO MARINE MAMMALS

Media Contact:
Jana Goldman, NOAA Research, (301) 713-2483 x 181 or Connie Barclay, NOAA Fisheries, (301) 713-2370 x 144