November 3, 2010 -- The latest discoveries and innovations in the field of acoustics (the "science of sound") will be presented this month at a major scientific conference in Cancun -- including better ways to power hearing aids, new technologies for monitoring fetal heartbeats, intriguing explorations of the origins of laughter and new insights into the social lives of dolphins.
The 2nd Pan-American/Iberian Meeting on Acoustics, sponsored by the Acoustical Society of America (ASA), the Mexican Institute of Acoustics (IMA), and the Iberoamerican Federation of Acoustics (FIA), takes place November 15-19. Research topics to be covered include architecture, animal communications, engineering, oceanography, medicine, music and psychology.
This press release is the second of a series highlighting newsworthy talks and presentations. Journalists may receive complimentary registration to this meeting using the information found at the end of this release. Reporters who cannot attend in person may cover the meeting remotely using ASA's World Wide Press Room, which will go live one week before the conference begins.
1) The Origins of Laughter and Sighs
Few things can stir up our emotions like the human voice -- from the joy that a peal of laughter brings to the terror of a scream.
But why we make certain sounds to express certain emotions is a puzzle that scientists are still working to solve. At the Max Planck Institute for Psycholinguistics in the Netherlands, Disa Sauter is finding clues by listening to deaf people laugh, sigh and shout. Her latest experiments suggest that some of the ways we express emotions are built-in, while others are learned through experience.
Sauter asked deaf participants to produce nine different types of emotional vocalizations. Listeners tried to determine which emotion each sound communicated, and the acoustic characteristics of each sound were compared to noises made by people with normal hearing. Because the deaf have never had the chance to hear other people making these sounds, they offer researchers a way to figure out whether these expression of emotion are innate in the brain or learned through experience.
Her data suggests that some sounds -- like laughter -- are fairly innate to the human brain: the laugh of a deaf person sounds much like the laugh of a person who can hear. But other expressions of emotions by people who cannot hear -- such as a cheer of triumph -- are virtually unidentifiable to people who can hear, suggesting that they are shaped by our experiences.
"There isn't one solution for all kinds of vocalization," says Sauter. "But for some vocalizations you need to have heard the sounds of other people."
Sauter is also comparing these results with a previous study -- which compared how people in different cultures express emotion -- to get a fuller picture of why we produce the sounds we do.
The poster "The role of perceptual learning in emotional vocalizations (5aSC12)" by Disa Sauter will be on Friday morning, November 19.
Dr. Sauter has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
2) Checking Fetal Health in the Womb
At Franois Rabelais University in Tours, France, Jean-Marc Girault is developing a system that would automatically assess the health of an unborn fetus by measuring key physiological characteristics.
"In utero, monitoring of fetal well-being or suffering is today an open challenge, due to the high number of clinical parameters to be considered," says Girault.
As a first step, he has developed a better way to count fetal heartbeats with ultrasound. Fetal hearts start beating at around 22 days of development. Current techniques for detecting this tiny pulse use a complex envelope Doppler signal -- which detects how the movement of a heart wall changes a beam of ultrasound energy. Unlike electrocardiography (EKG) measurements, ultrasound measurements are not impacted by the mother's heart rate. But price to pay is that other movements and information can bias fetal heart rate estimation.
Girault and his colleagues propose using directional Doppler, instead. This technique is less affected by the movements or pseudo-breathing of the fetus. His new technique can successfully measure and distinguish the fetus' heart rate from other movements and information 95 percent of the time. This improves the accuracy compared to current techniques by 75 percent.
"The good performance of our new detector is very encouraging and allows us to propose a 'fetal well-being electronic score' based on a reliable fetal heart rate estimation," says Girault.
The talk "Estimating fetal heart rate from multiple Doppler ultrasound signals (2aBB12)" by Jean-Marc Girault will be at 11:30 a.m. on Tuesday, November 16.
Dr. Girault has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
3) Coastal Dolphins Quieter than Thought
Dolphins are thought to be able to communicate with each other over vast expanses of ocean, between distances as far as 15 miles apart. Studies of dolphin whistles have suggested that they should carry that far in water, which transmits sound much better than air does.
To put this idea to the test, Frants Jensen of Aarhus University in Denmark dropped underwater microphones (hydrophones) into coastal waters near Bunbury, Australia and recorded the loudness of bottlenose dolphins. By combining this data with measurements of the background noise and how sound travels through water, he estimated that these dolphins would only be able to hear each other from a few hundreds of meters apart.
"It's the first time we've measured the source levels -- the loudness of the whistles -- in these tropical areas," says Jensen.
Compared to the open ocean, the coastal waters of Australia are fairly loud, with snapping shrimp and vessel noise crowded into the same frequencies that the dolphins use to communicate.
The range at which an animal can communicate is likely to have an effect on its social structure, says Jensen. Baleen whales and elephants, for instance, can talk to each other over vast distances, which is thought to allow them to stay in constant contact and easily find each other.
These dolphins' limited range of communication may be one reason they live fairly solitary lives in more fluid societies.
"Dolphins move a lot around in this area but don't associate closely with many other individuals," says Jensen. "Some males have alliances and swim together consistently for their lifetime, while females are a lot more individual and associate mostly with their own calves over time."
The talk "Bottlenose dolphin shortrange communication in a shallow, noisy environment (5aAB7)" by Frants Jensen will be at 10:15 a.m. on Friday, November 19.
Dr. Jensen has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
4) Sounding Out Ruptured Livers
The human liver, a highly vascularized vital organ, is the largest visceral organ and as such is vulnerable to traumatic injury. Blunt force can easy rupture the liver's capsule (the parenchyma) resulting in bleeding fractures.
Imaging these fractures non-invasively is difficult. Unlike tumors, which contain tissues of varying density that provide good contrast, the homogenous soft tissue of liver lacks contrast.
Traditional ultrasound imaging doesn't do that well with livers. That's because sound waves are pressure waves; they pulsate in the direction as the motion of the wave. Such sound waves probe the bulk modulus of the material -- its elasticity in the forward-backward direction.
By contrast, a shear wave moving through a medium imposes a pulsation of the atoms transverse to the movement of the wave. Shear waves probe the shear modulus, the stiffness, of the medium and can provide a much sharper image of the kinds of fractures that occur in livers.
Jiao Yu of the University of Washington in Seattle and her colleagues produced such shear waves by aiming a series of ultrasound pulses with successively deeper focal points in the material to be imaged. This, in effect, creates the desired shear waves. Their new studies look at liver tissue outside the body; the method is therefore at an early stage and not yet in clinical trials.
"We are investigating this method for imaging damaged livers," says Jiao Yu. "There is no non-invasive, robust, fast means for doing this currently."
She says she is not aware of any other lab investigating this imaging technique to detect liver trauma.
The talk "Detection of blunt force trauma liver injuries using shear wave elastography (3aBB1)" by Jiao Yu will be at 8 a.m. on Wednesday, November 17.
Dr. Yu has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
5) Mayan Pyramid Chirps like a Bird
Standing 79 feet tall, Chichen Itza's temple of Kukulkan is an impressive sight that has revealed much about the ancient Mayans to the keen eyes of archaeologists.
For acoustic scientists who study this temple and others like it, though, its looks are only half of the story. The sounds of the site, they believe, can enrich our understanding of the politics and culture of the people who once lived in this region.
"Once the Earth was a quieter place, and the ancients paid much more attention to what they heard in their environment," says David Lubman of DL Acoustics.
Lubman has studied the peculiar echoes that the temple at Chichen Itza produces. Visitors who clap hear the sound of their hands reflected back as an unrecognizable, high-pitched chirp -- a sound that some believe resembles the call of a bird.
To test this idea, Lubman recorded echoes from the temple and compared them to the noises made by the Quetzal, a bird native to this region that was an important part of Mayan culture. The temple was thought to be devoted to the god Quetzalcoatl, the "plumed serpent."
Sure enough, the spectrograms of both sounds bore a striking resemblance.
Dr. Lubman's presentation is part of a session devoted to the acoustics of prehistoric civilizations.
The talk "Acoustical solutions to archaeological mysteries at Chichen Itza's temple of Kukulkan (2pAA3)" by David Lubman will be at 2:15 p.m. on Tuesday, November 16.
6) Making Energy from Vibrations
When one thinks of cleanly soaking up energy from the surrounding environment, solar and wind energy come quickly to mind. Geothermal and ocean-wave energy are also being studied for use in making electricity. But what about the vibrations common to many heavy machines?
John McCoy, an engineer at the Catholic University of America in Washington, D.C., believes a lot of energy can be tapped in vibrations which otherwise go to waste in the form of heat, noise and wear.
"There is no law of physics that precludes harvesting a significant percentage of all the energy contained in vibrating structures," he says.
McCoy will discuss some of the studies that show how vibration energy can be turned to good account, especially in the built environment, such as subways, bridges and buildings. Current vibration-harvesting devices generally rescue energy at the milliwatt level, but McCoy believes that recovery rates can be much higher than that.
The talk "Vibration energy harvest: A basis for novel technologies" by John McCoy will be at 2:15 p.m. on Tuesday, November 16.
Dr. McCoy has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
7) New Power Source for Hearing Aids
Many implanted medical devices get energy from batteries, which eventually run down. Beaming energy through the skin is a useful alternative, especially for supplying cochlear implants, which require about 70 mW of power. Here the issue is whether to go with energy in the form of radio waves (RF) or ultrasound. For both methods about 10-12 percent of the beamed energy gets lost on the way as it moves through several millimeters of tissue, usually by being scattered rather than being absorbed. In both systems the overall energy efficiency is about 40-50 percent.
Rob Adamson, a researcher at Dalhousie University in Halifax, Canada, prefers the ultrasound approach, since the power source is much smaller: the RF coils are typically 5 cm in diameter, compared to 5 mm for the ultrasound source. Furthermore, the RF setup often requires an extra magnet (to keep the coils aligned), and this precludes the patient having an MRI scan performed without having the implant removed.
Adamson's ultrasound beaming device is not yet in clinical trials, but his lab is affiliated with an ear surgeon.
"We are reporting successful experiments in delivering power across a water bath using ultrasound with 38 percent efficiency," says Adamson.
The ultrasound approach might be useful for supplying energy to other such as artificial hearts.
The talk "A miniature, ultrasonic transcutaneous energy transmission system for powering implantable medical devices (1pBB9)" by Rob Adamson is at 3:50 p.m. on Monday, November 15.
8) Repelling Divers with the Sound of Their Breath
At the Stevens Institute of Technology in Hoboken, New Jersey, Alexander Sutin is developing a non-lethal weapon for protecting ports from underwater divers with malicious intentions -- an acoustic device that overwhelms them with the amplified sound of their own breath.
The technique may offer Homeland Security and the Navy a kinder, gentler method of non-lethal diver deterrent, an alternative to deadly underwater explosive charges or loud underwater sirens, which may impact marine life.
The idea is to detect the diver's breathing passively instead of using an active acoustic technology like a sonar ping. Sutin has recently returned from Holland, where he and a team of Stevens and Dutch scientists investigated passive acoustic methods of diver detection.
"Many fishes can produce similar signals to divers on active sonar, but fishes do not breath like humans" says Sutin. "Passive methods based on the breathing of a diver are such simpler and offer a much better detection rate."
The next step will be to develop a method to isolate a narrow band of the breathing sound and radiate it back to the diver. Using a technique called Time Reversal Acoustics, the scientists hope to produce an amplified beam of sound loud enough to overwhelm an intruder but focused enough to spare the surrounding wildlife.
Time Reversal acoustics has been successfully used to amplify acoustic signals to the level enough to destroy kidney stones.
The talk "Time reversal acoustic approach for nonlethal swimmer deterrent (2pBBa6)" by co-author Yegor Sinelnikov will be at 2:35 p.m. on Tuesday, November 16.
Dr. Sutin and Dr. Sinelnikov have written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
9) Why Some Voices Sound More Attractive
Some people's voices seem to have been made for the radio. Others grate on our nerves.
At the University of California, Santa Cruz, Grant McGuire is figuring out why. He's studying what acoustical features tend to make a human voice sound more attractive.
In data presented at an upcoming meeting of the Acoustical Society of America in Cancun, Mexico, he asked volunteer to listen to recordings of 60 people talking and rate how attractive they sounded. He then analyzed the acoustic characteristics of these voices.
"Males and females for the most part agreed on what an attractive male or female voice sounds like," says McGuire.
His study, which included only Californians, didn't set out an exact definition for "attractive" -- it left that up to the listeners. But it did find three features that tend to make a voice sound attractive.
First, we seem to like voices that use the same dialect that we do. The Californians preferred voices that pronounced the word "dude" with the fronted "oo" vowel that the West Coast is known for.
"The more Californian you sound, the more attractive you are going to be to other Californians," says McGuire.
Secondly, we don't like voices that sound creaky -- that slight rasp or rattle that some voices have. Instead, we prefer breathier-sounding voices.
"If you want to avoid having a creaky voice, don't drink a lot or smoke a lot," says McGuire.
Finally, the scientists found a connection between the size of man's vocal tract -- the distance between the vocal folds and the mouth -- and the attractiveness of his voice. Longer vocal tracts tend to cause different resonances in the voice that tend to be considered more attractive.
It's a connection that evolutionary psychologists, who seek to explain psychological traits as adaptations, find puzzling -- why, they wonder, would we prefer a longer vocal tract?
The poster "Phonetic correlates of vocal attractive in American English (5aSC9)" by Grant McGuire is on Friday morning, November 19.
10) Acoustic Archaeology Reveals Mayan Political Grandstanding
The temples of the Ancient Mayans played an important role in politics that can't be seen, but must be heard instead, according to Sergio Beristain, a researcher at ESIME in Mexico City -- they allowed leaders to effectively speak to throngs of people in an age before the megaphone.
"Many of these pyramids that were built for cultural and religious purposes were also used a lot for giving messages to the people," says Beristain.
Given the number of people who gathered at these sites -- crowds of as many as 10,000 people -- it would have been impossible for priests and political figures to address the masses from ground level.
Using microphones and recording devices, Beristain has measured the way that sound attenuates and disperses from the top of these structures, and found that a human voice could carry remarkably well and maintain its intelligibility.
Architectural features and walls may have helped to carry the sound farther.
"Because they are in a high position, everyone receives the sound from a good angle," says Beristain "From some of these pyramids, you could talk to someone a little over a hundred meters away without having to shout."
Dr. Beristain's presentation is part of session devoted to the acoustics of ancient civilizations.
The talk "Pyramids and basements (2pAA6)" by Sergio Beristain will be at 3:30 p.m. on Tuesday, November 16.
Dr. Beristain has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
11) Reevaluating Oil Rig Noise
In the wake of Deepwater Horizon spill, the federal government has implemented new drilling regulations and the oil industry has developed new safety standards to prevent another disaster. But for Michael Stocker, director of the non-profit Ocean Conservation Research, one area of petroleum safety remains woefully unfunded.
He says that it's time to take a hard look not only at the mechanisms for preventing spills, but also at the sound and vibrations that deepwater oil operations produce.
"These things can be real screamers," says Stocker. "When you have gas oil water and sand all moving at high pressures, it's just going to roar."
The BP oil spill was difficult to plug both because of the depth and enormous well-head pressures in excess of 13,000 lbs per square inch. When mixtures of oil, gas, brine and sand emerge from a reservoir at such pressures into a wellstem they can create loud broad-band noise. But these sounds have never been measured before using underwater microphones (hydrophones).
"Aside from anecdotal comments from people who work in the industry, we haven't had the opportunity to go out and measure this," says Stocker.
Deepwater oil production is one of many sources of noise in the ocean that have scientists worried. The world's ocean is steadily growing noisier with human activity many areas are 10 times louder than they were just 50 years ago from shipping traffic alone. Global expansion of deepwater oil exploration and production is exacerbating this problem. Some studies have shown that rising noise levels are disrupting marine animal communication.
For instance, seismic air guns -- which shoot loud pulses of air into the ocean to probe the seafloor for petroleum -- have been shown to disrupt whale migration and feeding behavior, as well as compromise fisheries catch rates.
"I'm not convinced that all of our new noise in the ocean is bad," says Stocker. "But there is ample evidence that some of our noises are harming whales and other wildlife."
The talk "New and developing seafloor petroleum extraction technologies: The noise of processing equipment operating in extreme environments (2pAB5)" by Michael Stocker will be at 2:25 p.m. on Tuesday, November 16.
Dr. Stocker has written a lay-language paper that describes this research in greater detail. It is available upon request and will be posted to ASA's virtual press room shortly before the meeting.
|Contact: Jason S. Bardi|
American Institute of Physics