An article in Renewable Energy World this month provides a great overview of ongoing research funded by the DOE that is assessing environmental impacts of “Marine and Hydrokinetic” energy technologies.  These new “MHK” systems include anything that generates electricity from the movement of water without dams, including systems that tap waves, tides, currents, or ocean thermal gradients.  Much of the research looks at the ways these systems can change the physcial dyanamics of ocean ecosystems (e.g., reducing wave height by drawing energy from the waves, changes in sediment movement and salt/freshwater mixing, etc.).  Of special interest here, of course, are the five studies (out of of 21 currently underway) that are looking at possible noise impacts.

Two are looking at areas where tidal turbine systems are in use or planned (Cook Inlet in Alaska and Admiralty Inlet in Washington); the Alaska study is looking for signs that beluga abundance or behavior is altered near a tidal turbine, while the Washington study is assessing existing background ambient noise and the acoustic footprint of a new tidal turbine.  Other studies are testing an acoustic deterrence system to see if it keeps migrating gray whales out of a proposed wave energy park and developing an acoustic detections system that could spot marine life around MHK installations.

Looking at the bigger picture, several other DOE-funded efforts aim to integrate MHK planning and site choices into larger marine planning and conservation initiatives. Two of these are developing protocols and best practices for siting, taking into account environmental and navigational impacts, and another, being undertaken by the Pacific Northwest National Laboratory, is working to incorporate siting of MHK projects into NOAA’s marine spatial planning efforts (essentially, ocean zoning, designed to minimize conflicts between various uses of the ocean).

Finally, the DOE is leading international efforts at the International Energy Agency to come up with international standards and shared knowledge banks on environmental effects of MHK installations, as well as mitigation practices.

Check out the full article, replete with links and detailed charts of all the ongoing research!

Note: The image above is a rendering of ORPC’s TidGen tidal and current turbine, which is being shown off this week at the EnergyOcean International Conference in Portland, Maine.

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.

A new research program at the University of Adelaide aims to learn more about the complex physical dynamics that create the primary noise in large wind turbines: the air turbulence off the trailing edges of the huge blades, which turn at speeds of up to a hundred miles per hour at their tips.

As explained in an article in AdelaideNow:

“If we can understand this fundamental science, we can then look at ways of controlling the noise, through changing the shape of the rotor blades or using active control devices at the blade edges to disrupt the pattern of turbulence,” said research leader Dr Con Doolan.

“Wind turbine noise is very directional. Someone living at the base might not have a problem but two kilometres away, it might be keeping them awake at night,” Dr Doolan said. “Likewise this broadband `hissing’ noise modulates up and down as the blades rotate and we think that’s what makes it so annoying.

“Wind turbine noise is controversial but there’s no doubt that there is noise and that it seems to be more annoying than other types of noise at the same level. Finding ways of controlling and reducing this noise will help us make the most of this very effective means of generating large amounts of electricity with next to zero carbon emissions.”

Further coverage is available from UPI.

A study just published is a tentative first step toward knowing where beaked whales may be foraging, and so perhaps avoiding exposing them to mid-frequency active sonar without having to see or hear them first.

The study, briefly described in this press release, found that beaked whales were more numerous in an area of their known habitat where salinity and temperature conditions increased the abundance of their prey.  Yup, that’s right:: they found that beaked whales congregate in areas where there are more fish they like to eat!!  Ain’t science great?

Seriously, though, such studies are important to ocean planners, as they provide the necessary causal data that can later (once the results are replicated elsewhere) be used to craft operational measures meant to protect beaked whales from harm.  These whales, which surface for only a few minutes at a time between 90-minute foraging dives, are notoriously hard to see, and not much easier to listen for, making it difficult to be sure whether they are nearby before a Navy ship begins sonar exercises.  The Navy has been reluctant to set aside potential habitat as “no-go” zones for their training, since even in possible habitat, there is no way to really know that animals are present.  Studies such as this one are small steps along the way toward getting solid enough data to know, more specifically, where whales may be more likely to congregate. Previous studies on harbor porpoises and bottlenose dolphins have shown how modeling habitat can be a powerful tool to inform spatially adaptive management of ocean predators.

The US National Renewable Energy Laboratory is about to begin a new study of the turbulent wakes that appear downwind from wind turbines.  Such turbulence can decrease the efficiency of turbines as well as creating physical stresses on the machinery; many researchers also suspect that inconsistent wind speeds across the rotor diameter contributes to increased noise.  It’s certainly easy to imagine that turbines inside the wakes pictured at the left (from an offshore wind farm in Denmark, where moisture reveals the normally invisible patterns) might be under stresses that would increase noise output.

For more on the NREL study, see this feature in Science Daily.

A new study finds that there is plenty of already disturbed land in the US to meet the 20% by 2030 goal for wind energy production.  Noting that habitat fragmentation is a key issue that can slow wind development, the researchers took a state-by-state approach that looked at both disturbed landscapes and wind resources, to see whether there is enough disturbed land (farmland, oil and gas fields, roads) on which to build out our wind future.

The answer: clearly yes. In fact, there’s enough disturbed land to build more than ten times the number of turbines needed.  While some states, including Maine, California, Pennsylvania, and Michigan, don’t have enough undisturbed land to meet their goals, many others have far more potential capacity than needed (see chart). “A disturbance-focused development strategy would avert the conversion of ~2.3 million hectares of undisturbed lands relative to the unconstrained scenario in which development is based solely on maximizing wind potential….Agriculture and oil and gas make up the vast majority of the disturbed lands identified in our analysis, such that removal of other disturbed lands would not qualitatively change our results. However, we believe that ridges surrounding abandoned surface mines and areas adjacent to existing roads also constitute disturbed areas where wind energy development should be considered.”

The researchers also note that “Placing turbines on disturbed lands may also benefit the expansion of transmission lines and associated infrastructure that will be critical to facilitate wind development. Because disturbed lands are already in areas of high road and transmission line density, they may ease the development of new or expanded transmission capacity. “

While their analysis focused on ground-based conservation needs, and so it is likely that some areas of bird and bat migration would need to be excluded from their disturbed-land analysis, there is enough extra potential capacity to easily move in this direction. What’s needed, they authors suggest, is policies that make it cheaper to build in disturbed land and more expensive to build on pristine land, which “could improve public value for both wind energy and biodiversity conservation.”

Read full paper online here.

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.

Researchers have determined that Americans between 25 and 64 years old hear better than their grandparents did at the same age.  Comparing research done in 1959-1962 with similar studies in 1999-2004, it appears that upper-frequency hearing is notably better than it used to be; middle-frequency hearing is roughly the same.

Researchers suspect that a combination of better treatment of childhood ear infections, fewer smokers and better health care in general, and a reduction in manufacturing jobs (as well as better hearing protection in today’s workplaces) have led to the improvement.

The reduction in upper-frequency hearing loss is especially important in speech recognition.

Women from three generations converse (NIDCD)

For more, see this NIDCD press release and this post on About.com that includes several related links.

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.

Two new studies on seismic survey impacts have been released by the Joint Industry Program (JIP) Sound and Marine Life research program, funded by oil and gas companies.

The first looked at the effectiveness of “soft start” ramp up of seismic survey airguns at night and at times of poor visibility.  This has become standard procedure, but there have been some concerns that if marine mammals were very close to the ship, even the low sound levels at the start of the ramp up could be loud enough to cause hearing damage.  Based on two different modeling approaches, the study found “no instances…in which the threshold levels for hearing injury for cetaceans were reached during the initial stages of the soft-start sequence. This suggests that the animals are not at significantly greater risk of harm when a soft start is initiated in low visibility conditions.”  Link to pdf of report at the website of the International Association of OIl and Gas Producers.

The second study aimed to address “the rarely-charted relationship between oil Exploration and Production (E&P) activities and trends in cetacean stocks.”  The study cites case studies involving populations of sperm whales in the Gulf of Mexico, humpback whales, blue whales and fin whales off the coast of California, northern bottlenose whales off Nova Scotia and harbour porpoises and minke whales off the east coast of the UK. The study, published in Aquatic Mammals,  provided new insights into the worldwide distribution of E&P activity in relation to marine mammal populations and has also revealed striking data gaps in our understanding of cetacean population numbers and trends. While the report’s review of seven stocks “found signs of an increase in numbers in one population (Californian humpback whales),” for the remaining six, “population trends could not be assessed due to the high variability in the abundance estimates.”  Link to pdf of this report.

In essence, there is not enough data to really tell us whether ongoing oil and gas activity has reduced stocks over the long term.  As usual in the many cases where ocean noise and population studies come up against this paucity of solid data, the researchers recommend that someone should fund of future studies ‘that provide more comprehensive data on cetacean stocks.”

JIP research page
Main JIP website

OGP publications page
OGP main page

In what must be one of the slowest EIS processes on record, the National Park Service and the Federal Aviation Administration is moving…methodically…to develop a new air tour management plan (ATMP) for Hawaii Volcanoes National Park.  After being upgraded from an EA to an EIS in 2005, the joint planning process began work on the EIS in 2007.  Four years later, rather than releasing a Draft EIS, the project planners have released a first draft of the proposed alternatives, and are asking for comment on these.  After incorporating comments, the DEIS will follow.  Sometime.

All ribbing aside, the fact is that this is actually one of the faster moving ATMP’s coming out of the seemingly uncomfortable partnership between the FAA and the NPS, which were  jointly charged in 2000 with developing ATMPs for all parks with existing or proposed flight tours.  The Park Service has taken a lead among federal agencies in addressing impacts on natural soundscapes of parks, while the FAA’s focus is more on air safety than resource protection.

“Hawai‘i Volcanoes is known for spectacular volcanic landscapes, significance of Native Hawaiian culture, Hawaiian species found nowhere else in the world, and for vast expanses of designated wilderness that stretch from summit to sea,” stated Cindy Orlando, Park Superintendent. “Whether it’s the crackling of new lava, song of a honeycreeper, or a magical Hawaiian chant floating across Halemaumau Crater or just silence—the soundscapes of Hawaii Volcanoes are unusual and valued as part of the park experience. We also protect some of the quietest places in the park service —secluded locations that are quieter than even humans can hear. Natural quiet is becoming an increasingly important attribute of the national parks.”

You can download a newsletter that shares the draft alternatives, and submit comments, from this page; see the full project planning website here; and check out a short video and news report on the process here.

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.

The latest in a series of studies looking at responses of beaked whales to Naval mid-frequency active sonar has provided some new details that reinforce our understanding that this family of deep-diving whales is extremely sensitive to noise intrusions.  The study, which took place on a US Navy training range in the Bahamas which is outfitted with seafloor recorders, found that beaked whales react to sonar signals below 142dB, and that they move an average of 16km away as soon as sonar operations begin, not returning until 2 to 3 days later.

It’s long been known that beaked whales tend to leave the range when exercises are taking place, but this study was the first time that some whales were tagged, to track exactly how far they went and how long they stayed away.

“Results… indicate that the animals prematurely stop vocalisations during a deep foraging dive when exposed to sonar. They then ascend slowly and move away from the source, but they do resume foraging dives once they are farther away,” said David Moretti, Principal Investigator for the US Navy.

“It was clear that these whales moved quickly out of the way of the [navy] sonars. We now think that, in some unusual circumstances, they are just unable to get out of the way and this ends up with the animals stranding and dying,” said Professor Ian Boyd, chief scientist on the research project. However, Boyd added “There is a tendency to blame the Navy for every stranding event and that is ridiculous.”

“Perhaps the most significant result from our experiments is the extreme sensitivity of these animals to disturbance,” said Boyd. “I am also worried that the general levels of sound that humans make in the ocean from all sorts of sources like ships, oil and gas exploration and renewable energy may be a much more serious problem for beaked whales and some other sensitive species.”

See good coverage from BBC and the Daily Mail, and read or download the research paper at PloS ONE.

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.

Great article in the New York Times on the strides made at Muir Woods, just north of San Francisco, in restoring natural quiet.

At times, deep within this vaulted chamber of redwoods, it is almost quiet enough to hear a banana slug slither by. For the National Park Service, that stillness is as vital a component of the site as the trees’ green needles, or the sudden darting rays of sunlight.

A decade after the agency resolved to restore natural sounds to this park in a metropolitan area of seven million people, managers at Muir Woods, in Marin Country just north of San Francisco, have made big strides in vanquishing intrusive noise. Now the background sounds are dominated by the burbling rush of Redwood Creek, the soft sibilant breeze that stirs the redwood branches, the croak of a crow.

Much more in the full article, including summary of National Park Service research on the effects of moderate noise on animals, and the recent Grand Canyon noise management plan.

Renewable Energy World has just published a commentary I wrote, urging wind industry professionals to reassess their current one-size-fits-all approach to community noise standards.  You can read it in full, with links to sources and comments from others, on their site.  They’ll be seeding it into their email newsletters during the week, likely triggering a few waves of readership and comments.

Here’s a pdf if you want to download it to read it offline. I’m reproducing it here as well:

Looking for Wind Industry Leadership in Reducing Noise Impacts

By Jim Cummings, Acoustic Ecology Institute

The wind industry is at an important fork in the road regarding community noise standards. After years of successfully using relatively small setbacks in farm and ranch country, recent years have seen a surge of noise complaints, troubling annoyance-level surveys, and widespread fear of new wind development.  Though sound levels of 45-50dB have been taken in stride by many, even most, places where early industrial wind development took place, it’s becoming apparent that for some types of communities, sound levels of even 40dB are triggering high levels of community push-back.  The industry’s first responses to this emerging problem have been counterproductive: discounting the prevalence of complaints, vilifying acousticians seeking to understand the shift, and most fundamentally, insisting to county commissions nationwide that “widely accepted” community noise standards that have worked elsewhere are applicable everywhere.  It’s high time that forward-looking industry insiders take the lead in forging a more flexible, collaborative relationship with communities, acknowledging that the noise tolerance we are used to is not universal: some rural regions are far less amenable to moderate, yet easily audible, turbine noise.  Companies that accept this fact — rather than ignoring or fighting it — will build corporate reputations that could make them the go-to developers across much of rural America.

A few tidbits highlight just how counterproductive the current entrenched “everything is fine” stance has become:

Read the rest of this entry »

The biannual Wind Turbine Noise conference, sponsored by the Institute for Noise Control Engineering Europe, is being held from April 11-14 in Rome.   This week, conference organizers announced the line up of papers that will be presented, and as always, it looks to be a greatly informative few days.  I can hardly wait until the proceedings CD is prepared, ordered, and arrives on my doorstep!

See Wind Turbine Noise 2011 website

See list of papers to be presented

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.”

A few days ago, Brandon Southall did a presentation on research that took place last year off the southern California coast, in which scientists successfully placed D-Tags on more animals than any previous study, then played sounds into the water, in order to watch for responses, and determine what sound levels trigger behavioral changes.  The Smithsonian talk was streamed live online, and is now posted for viewing at our leisure.

It can be viewed at:
http://www.ustream.tv/recorded/11956611

(Via Brandon’s SEA-INC blog):
SOCAL-10 presentation at Smithsonian available online – SEA Blog: “”

This is pretty amazing: researchers at CalTech working in biomimicry have completed the first field trials of an array of small vertical axis wind turbines, in which they pack the arrays tightly together, aiming to take advantage of possible boosts in output created by capturing the vortex flow patterns from each other.  The concept is modeled on studies of fish schools, and the realization that the move far more efficiently through the water than do individual fish.  Air pattern modeling and initial field tests suggest that these tightly packed arrays may generate 100watts per square meter, ten times the energy density of today’s industrial wind farms.  This could mean more energy in the same area, or, more likely, the same or somewhat more energy using far less land than today’s wind farms use.  With machines that are quieter and only 30 feet tall!

Energy per unit area of proposed tightly packed small turbines vs. several existing utility-scale windfarms

Each 30-foot turbine generates only around a kilowatt of output, as compared to today’s massive 1500-2500kw industrial turbines; this is the reason that all the many vertical axis designs have been considered only useful for home use, rather than utility-scale generation.  But the fish-inspired layout produced far more power per square meter of land used than today’s wind farms.  The first field test Read the rest of this entry »

Alec Salt, a Washington University scientist who studies the inner ear, has discovered that outer ear cells may respond to very low frequency infrasound, well below the frequencies that are audible or otherwise consciously perceptible.  Salt suggests that his discovery may help explain why some individuals seem to be more dramatically affected by low frequency wind turbine noise than would be expected.

The study, funded by the National Institutes of Health’s National Institute on Deafness and other Communicative Disorders, is a literature survey that looks especially at the physiological responses of guinea pigs exposed to infrasound down to 5Hz.  Humans can generally hear sounds as low as 20Hz; sounds below this frequency are called infrasound.  Guinea pigs are often used in lab studies, since their hearing mechanisms are similar to those in humans; in fact, human ears are more sensitive to low frequencies than are guinea pigs.  The crux of his findings center on the ways that hair-like cells in our ears, the Outer Hair Cells (OHCs) and Inner Hair Cells (IHCs), work together to translate sound pressure at various frequencies into the perception of sound in our brain.  For audible frequencies, the OHCs amplify the vibrations they receive from sound waves, triggering hair-like structures on the IECs to ripple and bend; it is this movement of IHCs that create the electrical (neural) impulses that our brain perceives as sound.

The surprise in Salt’s study was that OHCs also react to infrasound.  Rather than, as might be expected, simply not being affected by infrasound, OHCs are “highly sensitive” to it, Read the rest of this entry »

AEI lay summary of this recently published scientific paper (download paper):
Mann D, Hill-Cook M, Manire C, Greenhow D, Montie E, et al. (2010) Hearing Loss in Stranded Odontocete Dolphins and Whales. PLoS ONE 5(11): e13824. doi:10.1371/journal.pone.0013824

This paper generated a wave of press coverage upon release, most of it suggesting that the research found that stranded dolphins are predominantly deaf, and often focusing on the idea that exposure to shipping and other ocean noise is the likely culprit.  I must admit that when I first saw the headlines, I too thought this might be the smoking gun implicating chronic ocean noise in population-scale impacts, but as usual, the popular press had vastly oversimplified and distorted the actual findings.

Baby dolphin found stranded in Uruguay, November 2010

Deafness found in a less than a quarter of stranded animals

While, as noted in some press coverage, 1200 0r more dolphins strand each year in the US, this study looked at just 35 stranded cetaceans of 8 species that stranded between 2004 and 2009.  The big headlines focused on the fact that 57% of bottlenose dolphins had profound hearing loss.  This represents 4 of 7 individuals, who were deaf or close to deaf; one was clearly very aged (it had no teeth left), so the authors suggest this individual was clearly experiencing age-related hearing loss. One other species showed hearing loss in a significant proportion of individuals studied: 5 of 14 Rough-toothed dolphins had profound hearing loss (36%); two of these are considered likely to have been born with hearing loss (see below).

By contrast, none of the 7 Risso’s dolphins studied had hearing loss, Read the rest of this entry »

A month or so ago, new research by Aran Moody at Woods Hole was published and garnered a bit of press attention — perhaps largely because it involved squid, whose public fan base rivals that of their more “charismatic” brethren, the whales and dolphins.  I’ve been meaning to post about it, but didn’t get to it.

Just as well, because today, Canada’s MacLean’s magazine blogs the story just right, offering the best mix of science and why it matters that I’ve seen.  The key points are that squid appear more sensitive to low-frequency sounds or pressure waves (such as that perhaps preceding the approach of a whale, rather than the echolocation clicks of dolphins), and this could mean that shipping or seismic surveys may displace squid.  There’s also a chance that invasive squid species, such as the Humboldt squid decimating fisheries along the northeast Pacific coast, could be chased away with noise (oh, joy!).  Check out the full post at MacLeans here.