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This page includes archived research summaries of studies released in 2004.

For current research summaries: [GO THERE]

For archives of research studies released in 2005: [GO THERE]
For archives of research studies released in 2006: [GO THERE]
See also archives of our News Digest coverage of science results: [GO THERE]

Also, check the AEI Special Reports on the annual International Whaling Commission Scientific Committee meetings, which always include important new science results related to noise
[2004: GO THERE] [2005: GO THERE] [2006: GO THERE]

Sperm Whales Show Signs of Bends
Woods Hole Oceonographic Institute press release, 12/23/04 [READ PRESS RELEASE]
A team from Woods Hole has found evidence that sperm whales may suffer from decompression sickness, or "the bends." They suspect that sperm whales normally manage their surfacing behavior to minimize problems with such bubbles. They conclude that if such normal behaviors are interrupted by, for instance, noxious acoustic stimuli (such as sonar or seismic survey guns), there is the risk of acute problems from nitrogen emboli, as has been reported in beaked whales exposed to mid-frequency sonar.

The WHOI biologists found that bone lesions grow in severity with age, and are found in animals from the Pacific and the Atlantic Oceans. The lesions were found in animals that died up to 111 years ago, and there appears to be no increase in the lesion prevalence since the oceans were industrialized.

Moore and Early studied sixteen partial or complete sperm whale skeletons from the Pacific and Atlantic Oceans that had been archived in museums. They found a series of changes in bones attached to the backbone, namely rib bones, and other small bones in the sperm whale's tail region. The changes are patches of bone death as a result of obstructed blood supply to the joint surfaces of the bone.

The team found evidence of comparable bone damage to be present with increasing severity as the size of the individual whale increased. Only the calves appeared normal. In looking at the potential causes of the lesions observed, the biologists concluded that such a wide distribution in time and space made nitrogen gas bubbles from a decompression sickness-like syndrome the most likely explanation.

Speed Boats and Jetskis Spook Dolphins, though Presence of Boats Does not Decrease Numbers of Dolphins
Goodwin, L., and P.A. Cotton. 2004. Effects of boat traffic on the behaviour of bottlenose dolphins (Tursiops truncatus). Aquatic Mammals 30(2):279-283.
A study in Teignmouth Bay, UK shows that the presence of dolphins in the study area was unrelated to the number of boats present. When boats were stationary, the behaviour of dolphins did not differ significantly between boat classes; however, there was a highly significant difference in the response of dolphins to different classes of boats in motion. Speedboats and jet skis were associated with aversive behaviours, even when boats were not directly approaching the dolphins.

Dolphins Show Avoidance of 12kHz Acoustic Communication System
R.A. Kastelein, W.C. Verboom, M. Muijsers, N.V. Jennings, S. van der Heul. The influence of acoustic emissions for underwater data transmission on the behaviour of harbour porpoises (Phocoena phocoena) in a floating pen. Marine Environmental Research 59 (2005) 287–307.
To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network is currently under development: Acoustic Communication network for Monitoring of underwater Environment in coastal areas (ACME). Marine mammals might be affected by ACME sounds since they use sounds of similar frequencies (around 12 kHz) for communication, orientation, and prey location. If marine mammals tend to avoid the vicinity of the transmitters, they may be kept away from ecologically important areas by ACME sounds. One marine mammal species that may be affected in the North Sea is the harbour porpoise. Therefore, as part of an environmental impact assessment program, two captive harbour porpoises were subjected to four sounds, three of which may be used in the underwater acoustic data communication network. The effect of each sound was judged by comparing the animals’ positions and respiration rates during a test period with those during a baseline period. Each of the four sounds could be made a deterrent by increasing the amplitude of the sound. The porpoises reacted by swimming away from the sounds and by slightly, but significantly, increasing their respiration rate.

Blast Fishing: Measurement of Sound Intensity, Suggestions for Enforcing Regulations
Woodman, George H., Simon C. Wilson, Vincent Y.F. Li and Reinhard Renneberg 2004. A direction-sensitive underwater blast detector and its application for managing blast fishing. Marine Pollution Bulletin 49: 964-973
A good field study of a proposed hydrophone system that could be used to localize the source of dynamite blasting used illegally by fishermen. The study took place in a bay in Malaysia, and was able to determine the direction of blasts with high accuracy (.2 degrees), though the range (distance) was less precisely determined. Received levels were generally in the range of 180-195dB peak pressure (145-160dB equivalent energy) for blasts estimated to be 2-10km away, and in the mid 170s db peak (high 130s equivalent) for blasts estimated to be 10-20km away.

Sperm Whale Seismic Study in the Gulf of Mexico
Annual Report, Year 2
Jochens, A.E. and D.C. Biggs, editors. 2004. Sperm whale seismic study in the Gulf of Mexico; Annual Report: Year 2. U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2004-067. 167 pp.
[WEBSITE] (scroll down to MMS-2004-067)
This is a multi-year MMS study that is using passive acoustic monitoring and acoustic tags to learn more about sperm whale responses to human sound, specifically seismic survey airguns. This report covers field work done during the summer of 2003. A total of 11 D-tags were deployed for 80.5 hours of on-animal data collection. Preliminary estimates of received levels during the CEEs ranged from 145-155 dB. Additionally, 376 hours of high quality sperm whale recordings were collected by the acoustic monitoring system.

One finding of interest was that the R/V Kondor, an seismic vessel donated to the project by an industry consortium, had engine noise (propellor cavitation) that was much louder than the R/V Ewing. and which limited passive acoustic detection to ranges of under 1km; passive acoustic monitoring had to be transfered from the Kondor to the Ewing due to this problem. This raises the question of whether PAM is a widely applicable method of providing reliable monitoring on ships that have not been designed or tested for moderate sound levels. (note: the excessive noise was in mid frequency ranges, higher than would interfere with airgun data, but within the range of whale calls).

A second surprising finding was that the airgun sounds contained significant mid to high-frequency content, including some up to 12kHz, coinciding with the likely peak of sperm whale hearing sensitivity. Generally, airgun sounds are assumed to be primarily low-frequency (under 500Hz).

Excerpts from the Report:
A new tag design, called the DTAG-2, was deployed in 2003. This tag has an extended dynamic range as compared to DTAG-1, overcoming a clipping limitation with the latter that reduces the accuracy of received level estimates for loud sounds. The physical size and mounting arrangement of DTAG-2 are also enhanced to achieve longer attachment times. In practice, both D-tag designs were used in SWSS 2003. Three DTAG-1 tags were deployed with an average attachment duration of 3.8 hours, comparable to the average of 4 hours in 2002. In contrast, the 8 DTAG-2 deployments had an average attachment duration of 8.7 hours, a dramatic improvement. The 3-phase controlled exposure experiment (CEE) design we have developed requires at least 4 hours with 6 hours being preferred.

Beaked whales were sighted on two occasions during seismic operations and the mitigation procedure was invoked. Although this interrupted a calibration experiment, it did not curtail any CEEs: on the one occasion in which a CEE was abandoned following the mitigation procedure, the tag also released from the whale prematurely and would not have collected data through a full CEE. A key practical consequence of the 180dB mitigation radius was that the desired high level (160+dB) CEEs were not possible when the tagged whale was within a widespread group as was often the case in 2003. As no whale in the group could be exposed beyond 180dB and the available propagation models for the air-gun array were conservative, relatively low level CEEs resulted.sea turtles be exposed to sound levels above 180 dB re 1mPa RMS. A key limiting factor in 2003 was the formation of a large wide-spread group of sperm whales in the northern gulf perhaps in response to a pronounced eddy. This area coincided with an on-going seismic survey from vessel Neptune. Based upon our experimental design, to obtain independent samples of CEE response, we need to move at least 10 miles after each CEE. However, animals were scarce outside of the main accumulation and considerable time was spent trying to find whales distant from the Neptune.

To date, we have carried out 10 cruises focused on sperm whales in three different sites: the Gulf of Mexico, Mediterranean, and the north-western Atlantic. The combined database of 275 hours of tag recordings spanning 230 deep dives is a formidable resource for predicting the natural behavior of sperm whales. A team of scientists, post-doctoral investigators and engineers at WHOI will be working with this data in 2004. The analysis process is time-consuming on account of the density of data collected.

Examination of the data is in a very preliminary stage. However, we offer some early results here to exemplify how the above metrics can be used to assess response. A key finding has been that the spectrum of air-gun sounds heard by tagged whales varies enormously and can include significant high frequency energy (well above 1 kHz) coinciding with the likely range of maximum hearing sensitivity of sperm whales. Such high-frequency sounds had not previously been considered likely from air-guns and a production model for these is still lacking. One of our CEE trials (sw03_173b) has energy from the direct arriving air-gun sound at frequencies up to 12 kHz. This whale remained close to the surface in a resting mode throughout the CEE and began deep diving 10 minutes after the end of the CEE (though some social behavior at the surface complicates a conclusion of avoidance).

The work in 2002 and 2003 has shown that a passive acoustic method that uses two or three hydrophones deployed as either a vertical or large-aperture towed array can be used for tracking sperm whale dive profiles. The relative arrival times between the direct and surface-reflected acoustic paths are used to obtain the ranges and depths of animals with respect to the array, provided that the hydrophone depths are independently measured. Besides reducing the number of hydrophones required, exploiting the surface reflections simplifies automation of the data processing. In the long term, the ability to extract sperm whale range and depth information from towed arrays would be of great use in mitigation efforts by MMS and the oil industry in the Gulf of Mexico, because the sound field from an airgun array is highly directional, and knowledge of range and depth of a sperm whale is needed to accurately determine what sound levels foraging animals are receiving in the vicinity of an airgun array. Figure 4.5.4 presents one result from 2003 that shows how the ship inadvertently passed almost directly over a whale foraging at 500 m depth. Standard tracking methods would have placed this animal 500 m to the side of the tracking vessel. This result thus demonstrates how a real-time range-depth tracking system might aid mitigation efforts during seismic surveys. A peer-reviewed publication on these methods has been submitted, and a more robust array deployment for 3-D tracking during 2004 is being planned.

IWC Scientific Committee, 2004 Reports
Among the highlights of this year's International Whaling Commission meeting in Italy was a series of reports dealing with ocean noise issues. The Standing Working Group on Environmental Concerns hosted a mini-symposium on ocean noise, which generated a fascinating overview of recent research as related to noise and marine mammals. It is included as part of "Annex K" of the Science Committee Report, several sections are available for download below. Of special note is a presentation by Roger Payne that introduces some new research that suggests that the detrimental effects of an otherwise modestly damaging toxin can be dramatically increased with the addition of non-physical stress (in the early research, the addition of the smell of a predator caused a known toxin that otherwise led to very small mortality rates to suddenly skyrocket to 80% mortality); the implication is that stress caused by noise may increase the detrimental impacts of other known pollutant or food stresses on whales.

The full Science Committee Report contains detailed recommendations regarding ocean noise, including plans for a workshop on seismic surveys at the 2006 meeting and a section concerning the threatened western pacific gray whales and planned oil and gas operations in and around their feeding grounds.


Sperm Whale Seismic Study in the Gulf of Mexico
Annual Report, Year 1
Jochens, A.E. and D.C. Biggs, editors. 2003. Sperm whale seismic study in the Gulf of Mexico; Annual Report: Year 1. U.S. Dept. of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA. OCS Study MMS 2003-069. 139 pp. [DOWNLOAD REPORT(13MB pdf)]
This is a multi-year MMS study that is using passive acoustic monitoring and acoustic tags to learn more about sperm whale vocalizing and dive patterns, both "natural" and during controlled exposure to seismic survey airguns. This report covers the 2002 field studies, and was released in early 2004.

Acoustic tags, held on by suction cups, were attached to 19 sperm whales, and returned 76 hours of recordings (an average of about 3.5 hours each; the longest time a tag remained intact was 15 hours). Tagging of more than one whale simultaneously allows researchers to listen in on social exchanges underwater; this could be an important window into observing subtle reactions to airgun noise. A key goal of the study is to learn more about sperm whale behaviors in order to infer the biological significance of behavioral disruptions such as avoidance, social disruption (eg masking of vocalizations). Researchers also hope to gain a better sense of whether exposure to sound may increase the costs of foraging (eg disrupt dive patterns so that more energy is expended) or decrease foraging success. Twice during the cruise, tags remained on long enough to conduct controlled exposure passes of the seismic airguns. The ship remained about 4 miles away, resulting in a received level as measured by the acoustic tags of about 145dB. Dive rates and click rates (used to zero in on prey) showed no marked change during exposure to the airguns; however, the researchers add the caveat that this represents a very small sample at relatively low exposure levels. During the 2003 season, they hope to continue to develop their simultaneous tagging technique in order to increase the sample size, and to increase the exposure levels into the 150-170dB range.

Another notable result came from the passive acoustic monitoring. The sperm whale vocalizations were audible above the background noise only within about 4km; a standard model of propagation patterns gave similar results, and suggest that in deep water the vocalizations may be audible to 10km.

Procedings of the Workshop on Active Sonar and Cetaceans
Held at the European Cetacean Society's 17th Annual Conference, March 8, 2003. ECS Newsletter Number 42-Special Issue, February 2004. Order form: [DOWNLOAD ORDER FORM(pdf)]

Includes overviews with some detail of strandings of beaked whales in conjunction with mid-frequency active sonar exercises in Greece (1996), Madeira (2000), the Bahamas (2000), and Canary Islands (2002). Among the notable topics covered:

  • CIBRA research highlights the effectiveness of passive acoustic monitoring for identifying dolphin populations in an area. However, it is crucial to do 24-hour monitoring in order to identify sporadically vocalizing animals; vocal activity is significantly higher at night, so monitoring only during daytime operation of (for example) a sonar or seismic airgun operation would not be effective.
  • Roger Gentry (NMFS) suggests that navies should survey canyon areas (which they like to use for sonar exercises, since subs may hide in such places) for beaked whales before any exercises; he also suggests that navies avoid using multiple active sonars in areas containing canyons and surface ducts until the mechanism of injury that has been observed is understood.
  • Twenty-two areas were identified as beaked whale "hot spots" (ie areas with concentrations of beaked whale populations) in a first step toward the development of a comprehensive global database.
Elevated Noise Levels Cause Prolonged Loss of Fish Hearing
Amoser and Ladich. Diversity in noise-induced temporary hearing loss in otophysine fishes. J. Acoust. Soc. Am. 113 (4), Pt. 1, April 2003.
This study exposed two species of fish to high-intensity white noise (158dB). The non-vocal goldfish showed reduced sensitivity of up to 26dB immediately after exposure, and the vocalizing catfish had even more extreme initial hearing loss of 32dB. Hearing returned to normal levels after 3 days for the goldfish, but took 14 days for the catfish. Researches conclude that "acoustic communication is severely impaired when fish live in noisy environments....high noise levels such as those applied here would reduce the effective communication distance to a few centimeters at most..." Note: these sound levels ARE quite high, and exposure times were relatively long, 12-24 hours; these results suggest the need for followup research simulating typical exposures. It appears that TTS is not triggered by broadband noise levels less than 148dB SPL (personal communication, Ladich, 2005). Smith, Kane and Popper (Acoustical stress and hearing sensitivity in fishes: does the linear threshold shift hypothesis hold water?Journal of Experimental Biology 207, 3591-3602 (2004)) showed that exposure to noise at 160-170 dB caused TTS even after 10 minutes and that exposure for several days resulted in much longer recovery time than found in this study.

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