Two of the US’s most widely-respected ocean bioacousticians have called for a concerted research and public policy initiative to reduce ocean noise.  Christopher Clark, senior scientist and director of Cornell’s Bioacoustics Research Program, and Brandon Southall, former director of NOAA’s Ocean Acoustics Program, recently published an opinion piece on CNN that is well worth reading in full.  They stress the emerging scientific awareness that chronic moderate noise from shipping and oil and gas exploration is a more widespread threat to marine life than the rare injuries caused by loud sound sources like sonar.  Here are a couple of teasers:

Today, in much of the Northern Hemisphere, commercial shipping clouds the marine acoustic environment with fog banks of noise, and the near continuous pounding of seismic airguns in search of fossil fuels beneath the seafloor thunder throughout the waters. In the ocean’s very quietest moments, blue whales singing off the Grand Banks of Canada can sometimes be heard more than 1,500 miles away off the coast of Puerto Rico. But on most days, that distance is a mere 50 to 100 miles.

Whales, dolphins and seals use sounds to communicate, navigate, find food and detect predators. The rising level of cumulative noise from energy exploration, offshore development and commercial shipping is a constant disruption on their social networks. For life in today’s ocean, the basic activities that we depend on for our lives on land are being eroded by the increasing amount of human noise beneath the waves.

These stark realities are worrying. But emerging technologies for quantifying and visualizing the effects of noise pollution can help drive a paradigm shift in how we perceive, monitor, manage and mitigate human sounds in the ocean. Ocean noise is a global problem, but the U.S. should step up and lead the way.

Clark and Southall make three specific recommendations: to establish a more comprehensive network of acoustic monitoring stations in order to better understand our overall acoustic footprint in the seas; to encourage and accelerate development of noise-reduction technologies (especially to make ships quieter, and also to develop new technologies for oil and gas exploration and underwater construction that generate less noise); and a shift in federal regulations from avoiding acute injury, toward protecting ocean acoustic habitats and ecosystems.

AEI lay summary of the following paper:
Risch D, Corkeron PJ, Ellison WT, Van Parijs SM (2012) Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away. PLoS ONE 7(1): e29741. doi:10.1371/journal.pone.0029741
Read or download online (free)

An ongoing research project that monitors whale calls and shipping noise in Stellwagen Bank east of Boston Harbor has reported an unexpected reduction in humpback whale songs during an 11-day period in which their recorders picked up low frequency sounds from a fish-monitoring system 120 miles away.  If this data does indeed represent whales ceasing singing or moving away in response to the distant sonar, this would be the first clear-cut indication that discrete human noise events may affect marine mammal behavior outside the immediate area.  The authors note that these results could suggest that impact assessments need to consider effects at longer ranges, and that effects may occur at received sound levels much lower than those generally considered worthy of concern.  This study simply reports the reduction in singing; any longer-term effect that may have on the animals is unknown (these are not mating calls).

The reduction in songs occurred at a time of year (early fall) when humpback songs are beginning to increase in this area; on years when the fish sonar was not in operation, the numbers of songs steadily increased over the 33-day study period.  But in 2006, when the fish sonar was heard at Stellwagen Bank for 11 days (8 of which included sonar sounds for over 7 hours), the number of minutes per day when humpbacks were singing dropped, some days to zero.  The average (mean) number of hours of whale song dropped from about 75 in the previous 11 days to about 15 minutes during the time the fish sonar was heard, before increasing to close to 3 hours per day once the sonar transmissions ceased.

The figure below shows the data from each of three years.  For each year, there are 33 days of data, with the middle 11 days being the period (Sept. 26-Oct 6) in which the sonar sound occurred in 2006.  The open circles are the mean minutes/day for each 11-day period, with the rectangular boxes representing the upper and lower quartiles of data for each period; black dots represent one or two days in each period in which the calling rates for that day were unusually far outside the range for other days in that period.

Ed. note: Interpreting the results of vocalization studies is complicated by the fact that there is much variability in vocalizing rates, and response/sensitivity to human noise, from one animal to another; and similarly, in numbers of whales in the area from year to year.  (This acoustic data counts singing minutes, but not animal numbers, which must be monitored visually.)

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Over the past few years, new and relatively inexpensive new hydrophone systems have allowed biologists to place autonomous recorders in far more locations, collecting vast amounts of acoustic data that can help them to understand the population dynamics of marine mammals, as well as to monitor interactions and effects of human noise on marine mammal communication.  They’re also looking forward to learning more about individual and pod communication patterns.

But this flood of new data hits a bottleneck when it needs to be assessed by human listeners.  There are several robust automated call detection programs available, but even these must be checked by humans, who can hear similarities in calls or see patterns in the sonograms that present the complex calls as pictures of the frequency patterns.

To the rescue comes a new crowdsourcing project from Scientific American and Zooniverse, WhaleFM.  Individuals from around the world are invited to join the research teams from Woods Hole and the University of St. Andrews by matching new recordings of orcas and pilot whales with  known calls or call types (often associated with particular behaviors). While orca society is moderately well-understood, with many call types already identified, this aspect of pilot whale research is at an earlier stage, and users will help to decide which Pilot Whale calls match, and help in discovering whether the same call is make by one individual, one group, or across broad areas. For more on the project, check the link above, or this blog post from Scientific American.

Research summary of Francis, C.D., Ortega, C.P., Cruz, A. 2011. Noise pollution filters bird communities based on vocal frequency. PLoS ONE 6(11):e27052.

An ongoing research project in New Mexico continues to shed more detailed light on the question of how moderate human noise affects nearby wildlife.  In a study design that effectively separates out the impact of the noise from other habitat disruption effects, Clint Francis and his colleagues are finding that some species are displaced, while others seem to thrive in areas with coalbed methane compressor stations creating noise around the clock.  The most recent paper to be published by Francis et al finds that species that sing at lower frequencies are most likely to avoid the noisy areas, while those who vocalize at higher frequencies are more apt to be unaffected or even thrive.

While this research studies an area with oil and gas development noise, it’s likely that similar effects would occur in and near wind farms, which also produce predominantly low-frequency noise. And, as the authors note to conclude their paper: “At the community-level, we must still determine whether noise is an agent of ecological filtering for other taxa that rely on acoustic communication.”

Rather than doing the full AEI lay-summary of the most recent paper, I want to point you to the great summary already written by Caitlin Knight, biologist who studies the ways in which anthropogenic disturbance impacts animals, on her Anthrophysis blog.

David Dunn is a longtime friend and colleague to AEI here in Santa Fe, and in fact his underwater insect recordings were my first taste of the sounds of the natural world having the potential to be deeply strange and amazing, rather than “just” beautiful. So when he discovered that the bark beetles chewing their way through the piñon pines in the hills of New Mexico were making all sorts of bizarre sounds, and suggested publishing a CD to benefit AEI, I was all for it.

Since then, the bark beetle inquiry has taken on a life of its own, becoming a perfect expression of David’s longtime conviction that artists can contribute in significant ways to science.  The acoustic behavior and communication of bark beetles was previously unstudied by entomologists, and now he’s being called to consult with scientists studying not only the piñon pine beetle, but also the mountain pine beetles ravaging larger higher-elevation and higher-latitude pines, as well as insect pests of the non-beetle persuasion.

This past week, a long article appeared in several Canadian newspapers, providing the most detailed look yet at David’s beetle odyssey.  It’s an excerpt from a new book by Andrew Nikiforuk, Empire of the Beetle: How Human Folly and a Tiny Bug Are Killing North America’s Great Forests.  The article dubs David “the tree whisperer,” though so far he hasn’t quite figured out how to calm the outbreaks; in fact, the research so far seems to be leading more toward driving beetles crazy than calming them.  But after forgiving the headline writer, we can sink into he article itself, which is the most detailed, entertaining version yet of David’s beetle adventures.

The NY Times is hosting a field journal by Kate Stafford of the University of Washington, as she recounts her work as part of a team surveying for bowhead whales along Alaska’s north slope.  This recent post is a marvelous evocation of the soundscape of spring in those northern seas.  You should definitely go read the whole thing (there is an absolutely beautiful extended audio clip of a chorus of bearded seals, bowheads, and belugas, as well as shorter clips of each individually), but here are some teasers:

You can look across a vast expanse of ice, all white and blue and cold, and see nothing. The lead is choked with pack ice or sealed over with newly formed ice, and there is no movement or sound. With few birds, no whales and no bears, one might mistake the Arctic for a desert. But if you go down to the ice edge, pick a hole in the new ice deep enough to reach water and drop in a hydrophone (an underwater microphone), the cacophony is astonishing.

What I have come to enjoy just as much as listening is passing the headphones to someone who has never heard springtime in the Arctic. It is a rite of spring that would stun even Stravinsky.

Here in the Chukchi Sea the springtime soundscape is dominated, always, by the long trills of male bearded seals….Though we have seen only one or two bearded seals off Barrow, it is clear from the acoustic data that there are many of them trilling all at once and within only a few kilometers of the perch. (the photo, by Kate Stafford, is of one of the bearded seals that showed itself)

The low frequencies used by bowhead whales overlap the acoustic bandwidth in which large ships and oil and gas exploration produce sound. These manmade sources of noise are likely to increase background noise levels as summer sea ice continues to decline and shipping routes cross the Arctic during ice-free summers. It is possible that this increase in noise will affect bowhead whales in particular by causing them to change the frequencies they use to communicate or the duration of the calls they produce, or by restricting the ranges over which they communicate.

Conservation Magazine’s Journal Watch has a nice summary of an important new overview of acoustic monitoring (more at the link):

Computer and electronics revolutions have produced sound-recording gear that is “transforming the way we study individuals and populations of animals, and are leading to significant advances in our understandings of the complex interactions between animals and their habitats,” a multinational team of researchers writes in the Journal of Applied Ecology.

Using arrays that can include dozens of microphones, for instance, researchers have been able to closely track tiny birds through nearly impenetrable tropical undergrowth and map out their territories. And specialized sound-analysis software can even help researchers figure out the species, age, and sex of noisy animals. Acoustic arrays have also enabled scientists to figure out when birds, such as sage grouse and blackbirds, are calling in a particular direction, or when they are sending broader signals.

“The wide-scale application of acoustic recording and processing technology has the potential to transform the fields of ecology, behaviour and conservation biology,” the team writes. But it will take a little innovation – and some sharing — to make the most of the new tools, they add. One “pressing challenge” is developing better signal-processing algorithms; another is developing common technologies that researchers can share – as opposed to the “customized” systems now in use.

To hurdle these obstacles, the authors suggest scientists “set up a website or wiki to serve as a repository for collective experiences and knowledge” – or expand an existing resource, such as the Bioacoustics listserv. Overall, however, they believe “the future for bioacoustic monitoring in the terrestrial environment is bright.”

Blumstein, D., Mennill, D., Clemins, P., Girod, L., Yao, K., Patricelli, G., Deppe, J., Krakauer, A., Clark, C., Cortopassi, K., Hanser, S., McCowan, B., Ali, A., & Kirschel, A. (2011). Acoustic monitoring in terrestrial environments using microphone arrays: applications, technological considerations and prospectus. Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2011.01993.x

Related: See these two recent posts about related work being done by a team of researchers touting a new subdiscipline, soundscape ecology.

Two recent features on NPR looked at (and listened to) new academic research that is being framed as “soundscape ecology.”  Very similar to our work with acoustic ecology, the new discipline aims to be seen as a subset of the established field of landscape ecology, with a focus (naturally!) on the ways soundscapes can inform us about the health of habitats.

The first piece, from last month, was a 5 minute segment on Weekend Edition, with Bryan Pijanowski of Purdue and Jesse Barber of Boise State (who has also worked extensively with National Park Service researchers).  It can be heard (and read) here.

The second piece is close to a half-hour long, and is a conversation with Pijanowski and Bernie Krause of Wild Sanctuary.  It can be seen and heard here.

A ten-year study in the western Pacific has documented the ways that new humpback whale songs move through several distinct populations over the course of a breeding season. ”Our findings reveal cultural change on a vast scale,” said Ellen Garland, a graduate student at The University of Queensland. Multiple songs moved like “cultural ripples from one population to another, causing all males to change their song to a new version.” This is the first time that such broad-scale and population-wide cultural exchange has been documented in any species other than humans, she added. (Ed. note: researchers have also suggested that cultural patterns are passed among sperm whale populations)

Once a new song emerges, all the males seem to rapidly change their tune. Those songs generally rise to the “top of the chart” in the course of one breeding season and typically take over by the end of it. ”We think this male quest for song novelty is in the hope of being that little bit different and perhaps more attractive to the opposite sex,” she said. “This is then countered by the urge to sing the same tune, by the need to conform.”

More, including whale song audio, here.

Related story: Acoustic recorders reveal new humpback breeding areas in central Pacific.

Conservation Magazine highlights a fascinating new study:

A loud motor boat can be annoying. If you are a hermit crab, however, the sound could be deadly. Last year, researchers discovered that playing boat noise distracted the crabs, preventing them from paying attention to potential predators. It’s just one example of how human-created sounds can interfere with “biologically important decisions about food selection, mate selection, and predator detection,” a new review of animal “attention” finds.

The paper reviewed a wide range of research studying attention in many animals, and found that human noise can have either pros or cons for conservation; in some instances, we could use noise to disrupt animals causing habitat disruptions.  Overall, “we need studies that aim to better understand the population consequences of distraction on wildlife populations,” the authors conclude.

Franciso Lopez’s annual 2-week workshop in the Amazon offers field recordists an amazing opportunity to both explore the rainforest, and collaborate, learn, and create with a community of peers.  In recent years, the economic stresses we all feel have made it more difficult for sound artists to raise the funds for this unique experience.

This year, there’s a Kickstarter project going, which if successful will fund 6 artists for the trip, and assure that the program continues.  If you’re not familiar with Kickstarter, it’s an online platform where entrepreneurs, artists, and others raise funds for worthy projects and product development; in return for your donation, you receive some of the fruits of the enterprise.  In this case, recordings!  Pledges are made now, and the project only proceeds if they meet their funding goal, at which point your pledge is paid out.

Let’s make it happen!

US News has a good piece today on Bryan Pijanowski’s research team at Purdue, about how the new field of soundscape ecology may help us to understand ecosystem dynamics and changes.

This April, when you step outside and hear the first sounds of spring, you won’t be hearing just songbirds and buzzing insects, but aural evidence of an awakening ecosystem. The emerging science of soundscape ecology is building on the established field of bioacoustics to create a new way of gauging ecosystem health and diversity—by listening.

“Natural sounds can be used like a canary in a coal mine, as a critical first indicator of environmental changes,” said Bryan Pijanowski, an ecologist at Purdue University in West Lafayette, Ind.

Pijanowski and his colleagues outlined their vision of soundscape ecology in the March issue of BioScience. The new field will take a much broader approach to collecting and evaluating sound than ever before, although the authors caution that no coherent theory yet exists to categorize the ecological significance of all the sounds emanating from a landscape.

Scientists have been using sound as a tool for studying the natural world for some time, mainly through bioacoustics, the study of sounds made by animals. But most of these studies tend to focus on one or two individuals at a time, said Jesse Barber, a sensory ecologist at Boise State University in Idaho, who was not part of Pijanowski’s team.

“Using sound to try to discern something about the ecosystem as a whole is what is novel about soundscape ecology,” Barber said.

Follow the link at the top of this post to read the whole article.

This story has been floating around for nearly ten years now, but I hadn’t come across it until Treehugger posted on it this week.  Click on over there for their normal rich set of links out to related themes and other sources on this one.

The short version of the story is that there’s a whale, first heard in 1989 and tracked since 1992, that sings at 52Hz, significantly higher than other large baleen whales.  No one else sings at this frequency, and he or she also travels an annual migratory path that misses contact with concentrations of other whales.  Scientists speculate that this animal is either a hybrid of two species, or a remnant of an unknown species.  Either way, it’s a lonely life, calling at a frequency other whales don’t respond to, and may not even hear. The Good website has a link to the sound itself, as well as a podcast that tells more of the story.

A new study reveals yet another family of ocean life previously thought to be deaf actually use sound to avoid potentially dangerous areas.  It’s the latest fascinating study from a collaboration between British and Australian scientists that has been revolutionizing our understanding of the role of acoustic ecology in reef habitats. In this study, crustaceans that feed on plankton avoided reef sounds; such reefs are home to fish that would enjoy a crustacean lunch.

Many such small crustaceans are foundations of vast ocean food webs. Co-author Dr Andy Radford, who is leading a major project in Bristol to investigate the impact of anthropogenic noise on marine animals, said: “This highlights just how damaging the impacts of human noise pollution may be for so many different creatures.  Chronic noise from shipping, drilling and mining may mask crucial natural sounds, causing animals to make poor or even fatal decisions, which in turn will threaten vital fisheries and tourism resources.”

Coral reefs are noisy places, and this noise can be an important cue for animal orientation. Dr. Steve Simpson is quoted in a University of Bristol press release: “The combination of clicks, pops, chirps and scrapes produced by resident fish, snapping shrimp, lobsters and urchins can be detected with our hydrophones from many kilometres away.  Our research has already found that reef noise is used by the larvae of fish and even corals to locate and select habitat after their early development in the open ocean, but using noise to avoid reefs, that is a first.”

The mechanism of hearing in these tiny creatures is poorly understood, although co-author Dr Andrew Jeffs and his group from the University of Auckland have found that both tropical and temperate water crabs and lobsters are attracted by the noise of their adult habitat.  Dr Jeffs said: “It is clear that some crustaceans use sounds for orientation, and that noise can induce a downward-swimming response. But this study throws wide open our understanding of crustacean hearing, and much more research is now needed to understand how and what these little critters can hear.”

Jump on over to Scientific American to read this great overview of the many different ways that animals are using to adapt to increasing human noise in their habitats. The author is an NYU science reporting student, and she promises a new sound blog soon on Scienceline….

Can you hear me now? Animals all over the world are finding interesting ways to get around the human din

Paul Spong and Helena Symonds are legends in the field of whale research; since the early 1970’s they’ve dedicated themselves to studying orcas from their independent lab on an island between Vancouver Island and the mainland.  Over those many years, they’ve accumulated 20,000 hours of tapes, which are now being digitized and cleaned up (to remove hiss and other noise and make the orca calls more prominent) by George Tzanetakis of the University of Victoria.  A recent article in the Toronto Globe and Mail focuses on Tzanetakis’ work, which is being posted online for researchers and curious listeners as the Orchive.  The entire collection isn’t online yet, but there’s plenty!

Those of us  who know the pleasures of cueing up Newport Jazz or good ol’ Grateful Dead shows from online taper archives like Archive.org and Bill Graham’s Wolfgang’s Vault will be familiar with the scope of this project: right now I’m nearly half-way through a 45-minute “set” from 9/1/05 known on the Orchive as Tape 449A.  As with jam band and jazz taper archives, the quality is decent though not crystal clear, creating a great background stream of pleasurable audio, ebbing and flowing from quiet and calm to more active, interspersed with moments of truly exciting interplay and melodic joy.  The audio is presented with a basic spectrogram, and even field notes (the scientific version of Dick Latvala’s show notes):

A sweet set from 9/1/05

Visit the Orchive!

A key research paper from National Park Service and Colorado State scientists has been published in Trends in Ecology and Evolution.  The paper, which got a lot of press when it was first made available online in the fall, introduces two key new metrics for measuring the effects of noise on animals.  The first, “alerting distance,” is the distance at which sounds can be heard: these may be sounds made by a species to alert others to danger, or sounds made by predators (which prey animals want to hear, so as to take cover).  The second, is “listening area,” the full area around an animal in which it can hear other animals’ calls, footsteps, and wingbeats.  A key insight offered by this approach is that even moderate increases in background noise (from nearby roads, airplanes, or wind farms) can drastically reduce an animal’s listening area.  The paper, which was free while in pre-press, is now available only to subscribers to the journal or other academic journal services; an article published in Park Science magazine and free to view online introduces much of the same material (be sure to click on the links to the figures, as they illustrate the concepts very well): see the article here, and check out the entire special soundscapes issue of Park Science here.

A very good article in the Aspen Times introduces the research, and includes many extremely insightful quotes from the researchers.  Go read the whole article! Three bits that are especially worth keeping mind are:

• “The male sage grouse, in its mating displays, produces high-frequency popping sounds and swishing sounds,” Fristrup said. “It also uses a low-pitch hooting sound, which carries the farthest from the display area as a long-distance advertisement. The danger is, it doesn’t take a lot of noise to substantially reduce the range at which females or other males could hear that low-frequency hoot. So the attraction radius of the display ground could contract substantially with the inability to hear a hoot.” The authors note that some species can reduce the effects of masking by shifting their vocalizations. This is especially true when members of a species are communicating with each other. However, when the sounds a species depends on emanate from another species (such as a mouse burrowing under the snow, which an owl needs to hear as it hunts), there is less room for compensation.
• Carnivores like lynx, who sit at the top of the food chain, can be particularly sensitive to habitat degradation of any type — including auditory — since each individual requires a huge hunting territory. “If one part of the range of a top-level predator is compromised, it may not take much to squeeze it out,” Fristrup said.
• Contrary to what one might expect, noise is not always more disruptive when it’s louder. Snowmobiles or cars, for example, might be less disruptive to elk or deer than a hiker or cross county skier would be. “There’s pretty good evidence that so-called quiet use can disturb wildlife. If it’s a noisy source, the animal perceives it a long way off and can track its progress. There are no surprises, and it can go on feeding or doing whatever else. A quiet sound, like a snowshoer’s footstep, is only perceptible when it is very close, potentially startling the animal,” Fristrup said.

To read AEI’s detailed lay summary of the research paper, published here in December, see this link.

This one slipped past me when it happened last June, but it’s well worth noting now.  Complicating assessments of the risks of bird deaths at wind farms is the fact that two-thirds of migrating bird species migrate mainly at night; Cornell’s Bioacoustics Research Program, which has already done groundbreaking work in elephant communication and underwater listening systems, has proposed that combining their autonomous recording devices with radar data could provide the missing information on exactly when and where concentrations of migrating birds may exist near proposed wind farms.

A compelling animation highlights the large-scale patterns: The color-coded radar map illustrates areas of precipitation over the coasts as well as vast movements of tens of millions of birds, bats and insects across the entire country. In the densest areas, the color-scales indicate movement of 2,000 birds per cubic kilometer. ”You’re talking about a massive movement of birds overnight,” said post-doctoral fellow Andrew Farnsworth.

Radar imagery of night-migrating birds, bats, and insects

Although radar data can show the magnitude, location, timing, speed and direction of migration patterns and provide information on key stopover sites, they do not identify types of birds or accurate flight altitudes, Farnsworth said. But combining radar data with data from flight call recordings and tracking tags on birds could allow researchers to identify many species in key areas. Bioacoustics program director Chris Clark added that recorders are cost effective, can be automated for many months at remote sites, provide data on many species simultaneously, increase the probability of tracking secretive and endangered species, and could allow regulatory agencies to develop computer models to assess risks to birds from wind turbines. He acknowledged, however, that using such acoustic technology could produce a massive “data crunch”; a single microphone over a three-to-four-month period can record 120 to 140 gigabytes of data, so data from several hundred microphones would be too much to process without advanced software. Also, researchers would need to better recognize the wide variety of flight calls and learn to integrate data from radar with those from acoustics and tracking tags, he added. More research is needed, Clark stressed, to determine at what altitudes species tend to fly and whether birds sense turbine blades and avoid them.  Read full account of the presentation in the Cornell Chronicle, with link to the radar map animation.

In the most promising development yet in using acoustics to deal with the spread of bark beetles in the American and Canadian west, researchers at Northern Arizona University have found that some beetles can be disrupted by playback of other beetle sounds. The tiny insects make squeaking noises as they tunnel through trees; the researchers have been manipulating the beetle sounds, which are above human hearing, and playing them back to the insects. The results drive them buggy: They attack each other, scamper in circles rather than straight lines and have tried to gnaw their way through Plexiglas covering a cross section of a tree in a lab in Flagstaff, Ariz.

A great article in The Missoulan included these tidbits from NAU researchers Richard Hofstetter and Reagan McGuire, Skye Stephens, an entomologist with the Colorado State Forest Service, and David Dunn, a sound artist who discovered and first recorded the beetle sounds:

“One of the questions is if we could effectively remove them from a particular tree or set of trees, where do they go, what happens to them?” Stephens said. “I’m very excited to see what happens next” with the research. Hofstetter and McGuire are eager to run tests on the ground to answer questions like that. Working with Dunn, they have applied for a patent on a device that pumps in noise to throw off the beetles’ destructive course. Hofstetter said the sounds are at a frequency that shouldn’t bother other species. The work has been a side project for the professor, who has struggled to scrape together funding for the research. McGuire is volunteering his time. ”We’re hoping it’s going to lead to a whole new field,” Hofstetter said.

David Dunn, who has traveled the world collecting sounds of nature for his compositions, first started recording the inner life of trees in 2004. He took the kind of small microphone used in greeting cards to record and play, fastened it to a recycled meat thermometer and inserted it into the tree. While concerned about the dying trees and what they signal about climate change, Dunn has become intrigued by the beetles, “an absolutely fascinating form of life. I fell in love with them,” Dunn said. “But then we’re watching them cannibalize each other. I always think, ‘How bad is this karma?’

“But if something really positive about forest health comes of it, perhaps it’s worth the price.”

Dunn’s CD, The Sound of Light in Trees, was released by EarthEar; 100% of all sales revenues are donated by Dunn and EarthEar to support the Acoustic Ecology Institute.  See more on the CD and beetle project on AEI’s website.

This came out in December, but I forgot to post about it then.  The National Park Service’s science magazine has published an entire issue devoted to the NPS’s soundscape studies and programs.

A couple strolls through Cathedral Grove on a quiet morning in winter when visitation is typically low. Signage at the entrance to this area reminds visitors that they are in a quiet zone. (NPS Photo/Lou Sian)

Articles include:

• Measuring and monitoring soundscapes in the national parks
• Integrating soundscapes into NPS planning
• Conserving the wild life therein–Protecting park fauna from anthropogenic noise
• Soundscapes monitoring and an overflight advisory group: Informing real-time management decisions at Denali
• Soundscape management at Grand Canyon National Park
• Generator noise along the US-Mexico border
• A program of research to support management of visitor-caused noise at Muir Woods National Monument

And, as they say, much, much more!  See the issue online here; from there, you can read every article in full. Note that the html views break each article into several separate pages, but you can also view in a “printer-ready” format that loads the entire article into a FlashPaper format, or you can view or download the full articles as pdfs.

Gordon Hempton, aka The Soundtracker, is featured on the Newsweek website this week.  Gordon shares his well-crafted gospel of quiet in both an interview and a very nice little video produced by Newsweek (there will be a pause after you click the play button, during which you will see a blank screen, rather than the commercial viewed at the Newsweek site):

I’ve just finished reading what must be the most exciting research paper I’ve seen this year, barely nudging out a similar paper addressing terrestrial noise impacts. A small group of researchers, with Chris Clark of Cornell as the lead author, took a giant step forward in addressing the impacts of ocean noise on the communication ranges of whales.  They came up with a clear and strikingly rigorous set of new metrics that will allow researchers and ocean planners to have a much more practical picture of how numerous noise sources combine to create cumulative impacts on acoustic habitat.  The new approach centers on the “Communication Space” of individual animals, as well as groups, and provides an intuitively obvious way to both imagine and assess the effects of ocean noise – measuring the area in which an animal can hear or be heard by others of its species.

My formal “lay summary” of this paper is reprinted in full below the fold, and I encourage anyone with a deep interest in ocean noise to read through that five-paragraph overview, or to download the paper yourself.  The key takeaway for those of you with a more casual interest in these issues is that in the test case that they used to illustrate their new approach, the researchers found that shipping noise has dramatically different impacts on different species, even though all three species they studied are low-frequency communicators.  In the area off Boston Harbor that they investigated, the critically endangered right whale is by far the most affected by shipping noise: on a day when two ships passed through the area (the average is often six), right whale Communication Space was reduced by an average of 84% over the course of the day, with several hours in which they could hear and be heard in an area less then 10% of that which would be expected without shipping nearby. Since right whales call back and forth to find each other as they form groups for feeding, this is truly worrying (though the key question of how a reduced communication range actually affects animals remains unanswered).  Fin whales and humpbacks were far less dramatically affected, with their Communication Spaces reduced by just 33% and 11% respectively.

These first examples focus on the effects of low-frequency shipping noise on low-frequency communication by large whales, but this approach can easily be used to address mid- or high-frequency noise sources (sonars, airguns) and higher frequency animal sounds such as those used for echolocation, opening a vast and exceedingly useful new doorway for biologists and ocean managers, as well as the general public, to appreciate the impacts of human sounds in the sea.   (click through for complete lay summary)

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An ongoing research project from the National Park Service Natural Sounds Program is about to publish a groundbreaking paper that outlines the many ways that even moderate increases in human background noise can create major impacts on animals.  The study proposes a new metric for use in bioacoustics research, the “effective listening area.”  This is the area over which animals can communicate with each other, or hear other animals’ calls or movements; as might be expected, animals focus especially on listening for sounds at the very edges of audibility, so that even a small increase in background noise (from a road, wind farm, or regular passing of airplanes) can drown out sounds that need to be heard.  The authors note analyses of transportation noise impacts often assert that a 3dB increase in noise – a barely perceptual change – has “negligible” effects, whereas in fact this increased noise reduces the listening area of animals by 30%. A 10dB increase in background noise (likely within a few hundred meters of a road or wind farm, or as a private plane passes nearby) reduces listening area by 90%.

In addition to introducing this important new metric, the paper provides a good overview of previous research that has addressed the impacts of moderate noise on various animals, including bats, antelope, squirrels, and birds.  The paper will be published next year, though an “in press” version is available for download.  A recent BBC article also covered this important new work.  A full detailed lay summary of this paper, as previously published on AEI’s science research page, appears below the fold: Read the rest of this entry »

A test run of one of the most promising new acoustic monitoring technologies is underway in Hawaiian waters: a six-foot long autonomous glider has been outfitted with a hydrophone, and has likely picked up foraging clicks of beaked whales.  University of Washington scientists did the glider’s engineering, while Oregon State researchers developed software to identify what is being heard.  ”We believe we have identified beaked whales,” says OSU’s David Mellinger. “It was pretty exciting. You work a couple of years on a project, hope it will succeed, but you don’t know until the equipment is wet.”  The current glider deployment, which began on October 27, is scheduled to end on November 17.  Here at AEI, we take special pride in this research, since Mellinger is one of our founding board members!

APL-UW's Jason Gobat and Jim Mercer and a ship crew member retrieve a Seaglider that had traveled a quarter of the way across the Pacific Ocean gathering oceanographic data

Read more about this study at Nature News, and see real-time records from the glider itself at the bottom of this page at UW (check this map to see all currently deployed gliders, though the others are not doing acoustics research).  You can also read more about UW’s glider research at their Applied Physics Lab website, and see this presentation on acoustic glider research from a different research team.

A five-week beaked whale Behavioral Response Study in the Mediterranean concluded in early September with a mixed bag of results: while researchers were unable to affix D-tags to any beaked or pilot whales, they were quite successful in using a new mobile Passive Acoustic Monitoring system which could be very useful in years to come. The study was largely aiming to track whales’ responses to various (low to moderate) levels of mid-frequency active sonar sounds using D-tags on the animals; previous Behavioral Response Studies using such “controlled exposures” have taken place on Navy instrumented ranges where the local populations are presumably familiar with sonar sounds, so they may respond differently than whales who have not heard these sounds before.  However, due to many periods of rough seas, as well as the inherent difficulties of finding, getting close to, and attaching tags to beaked whales (who dive for over an hour and come to the surface only briefly), no D-tags were deployed on whales, and no controlled exposures took place. However, a document prepared before the cruise, summarizing previous BRS results, is well worth reading: see especially page 8, which includes a detailed analysis of beaked whale responses to sonar and orca sounds: in both cases, the whales cut short foraging dives, but returned to the surface more slowly than normal, not more steeply as is sometimes assumed, and they clearly moved directly away from the sounds.

Beaked Whale (click for cruise blog home page)

However, researchers made the most of two other purposes of the cruise, both of which made use of a new passive acoustic monitoring technique.  The research took place on an extremely quiet research vessel, from which two hydrophone streamers were deployed, each of which had two hydrophones on it.  This gave listeners on the ship four separated sources from which to record and analyze sounds, so that most sounds could be quite well localized (direction and distance).  In addition, researchers deployed floating “sonobuoys” that provided more listening stations during times when groups of beaked whales were nearby.  This network of hydrophones provides much of the information that is provided by permanent bottom-mounted hydrophones on Navy ranges, and offers the potential to both find and monitor beaked whales in any location.  The hydrophone arrays were also collecting basic sound budget data, which will provide a better sense of the noises (both natural and man-made) that ocean creatures hear on a routine basis.  Click through for links to specific blog posts of interest, and a description of one day’s close encounter. Read the rest of this entry »