Deteriorating screws in bridges, fish that listen in the dark, medical devices that use sound to treat disease, the detected comeback of a long-gone whale, the sound of hyenas, cheese, and bagpipes, and what evolution can teach us about cowardice.
These are just a few of the topics that will be covered at the 157th meeting of the Acoustical Society of America (ASA), which convenes from May 18-22 at the Hilton Portland&Executive Tower in Portland, Oregon. There, acoustical scientists and engineers will present more than 1,000 talks and posters related to acoustics, a cross-section of diverse disciplines devoted to architecture, underwater research, psychology, physics, animal bioacoustics, medicine, music, noise control, and speech.
1) WIMPS HEAR DANGEROUS NOISES DIFFERENTLY
Scrawnier people are more likely to perceive an approaching sound as closer than it actually is. This connection between physical fitness and the brain's auditory system may have evolved to help the weak get out of the way of approaching danger.
That's the latest finding of evolutionary psychologist John Neuhoff and colleagues at The College of Wooster in Ohio, who study "looming" sounds. Participants in their study listened to a tone moving toward them and pressed a button when they thought the sound had arrived directly in front of them. Nearly everyone pushed the button too early, which Neuhoff interprets as an adaptation that helps human beings to anticipate and avoid danger.
The team also tested the fitness levels of the listeners and found that those better equipped to handle danger allowed the sound get closer. Individuals with greater upper body strength and/or stronger cardiovascular systems waited longer to push the button, while subjects in poorer physical shape gave themselves a greater "margin of safety."
The research expands upon previous work showing that women respond to looming sounds sooner than their typically larger, stronger male counterparts -- though both groups perceive receding sounds equally. Rhesus monkeys also spend less time looking at receding sounds than approaching sounds. "These reactions are influenced by evolutionary forces; it's a good thing to respond a little bit early and, evolutionarily, it doesn't cost much," says Neuhoff.
The talk "Strength and cardiovascular fitness predict time-to-arrival perception of looming sounds" (4aPP7) by John Nuehoff is at 11:00 a.m. on Thursday, May 21. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa840.html
2) FISH THAT LIVE IN THE DARK HAVE THE BEST EARS
All fish have ears buried inside their heads. But fish that live in the deepest, darkest waters of the ocean may have particularly sensitive ears says Xiaohong Deng of the University of Maryland. She will be presenting the first anatomical evidence suggesting that some deep-sea fish have specialized structures to heighten their hearing.
The types of fish that Deng studies live in layers of the ocean that no sunlight can reach -- from 400 meters all the way down to depths of 4,000 meters. Biologists are currently unable to keep these mesopelagic and benthopelagic fish alive for very long at the surface, so knowledge about how they function comes from comparing their anatomy to other kinds of fish that live in surface waters.
Some of these deep-sea fish have adaptations similar to those of surface fish with heightened hearing: a connection between the swim bladder and the ears, which may help to amplify sounds to the ears; and elaborately-oriented hair bundles in the inner ear, which suggests better hearing than fish with less complex patterns. Some of the deep-sea fishes also have a variety of unusual structures not found in other types of fish, like exceptionally rigid ears and stalks projecting from stones in the ear. The functions of these newly-discovered parts are unknown.
Deng will present detailed images of these structures and discuss her plans to work out their physiological purpose. "We have already found many specializations and adaptations in the eyes and olfactory systems of deep-sea fishes; it is reasonable to think that their hearing should also be important in the dark," says Deng.
The talk "Comparative studies of the auditory periphery of deep-sea fish" by Xiaohong Deng is at 3:35 p.m. on Monday, May 18.
3) GENE-LADEN BUBBLES GROW NEW BLOOD VESSELS
Progress in human gene therapy -- the insertion of therapeutic DNA into tissues and cells in the human body -- has been slower than expected since the first clinical trials in 1990. One of the biggest challenges for this technology is finding ways to safely and effectively deliver genes only to the specific parts of the body that they are meant to treat. Cardiologist Jonathan Lindner of Oregon Health and Science University will discuss his latest experiments in gene therapy, which use microscopic bubbles chemically modified to stick to the cells that line blood vessels.
This technique, ultrasound-mediated gene delivery (UMGD), exploits the properties of contrast agents, microparticles that are normally injected into the body to improve the quality of ultrasound images. In UMGD, the tiny particles are microbubbles composed of pockets of gas encapsulated by thin membranes that are coated with DNA before injection. A targeted pulse of ultrasound energy "rings" the bubbles like a bell, popping them in a specific location and releasing the DNA into the surrounding tissue.
To improve the specificity of this targeting, Lindner grafts long arm-like molecules to the outside of the bubbles. These arms, which do not interfere with the DNA attached to surface, are designed to recognize and bind to molecules on the outside of specific cells in the body, allowing the bubbles to attach to a tissue before being popped. In theory, this should improve both the specificity and efficiency of the gene therapy.
Lindner created an arm designed to attach to endothelial cells lining blood vessels. He will present data evaluating the behavior of these "targeted" bubbles in living tissue. The ability to stick these gene-laden microbubbles to the lining of blood vessels increased the amount of gene transfection. This strategy may be particularly important for delivering therapeutic DNA to the walls of blood vessels. For example, Dr. Lindner and collaborators have successfully stimulated the growth of new blood vessels using UMGD with microbubbles carrying a gene for vascular endothelial growth factor. This therapeutic use could be important for treating ischemia in patients who have had a heart attack, peripheral artery disease, or stroke.
The team is also investigating using the bubbles to transport small doses of drugs. "If you're trying to deliver a nasty drug to part of the body, this may be a way to improve safety," says Lindner.
The talk "Targeted microbubble technology and ultrasound-mediated gene delivery" (4aBB2) by Jonathan Lindner is at 8:20 a.m. on Thursday, May 21, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa791.html
4) SINGING SCREWS REVEAL SICK STRUCTURES
In 2006, a concrete panel weighing several thousand pounds fell onto traffic in Boston's Big Dig tunnel, crushing a car and killing a motorist. The alleged cause -- and subject of a multi-million dollar settlement -- was faulty epoxy that allowed bolts in the ceiling to wiggle loose. Mechanical engineer Joe Guarino of Boise State University in Idaho is developing an early warning system to prevent such catastrophic joint failures in the future. His team listens to the sounds made by vibrating bolts. Their analysis of how these sounds change as the bolts unscrew has revealed certain frequencies in these noises that could be monitored to check the health of bolts in buildings, bridges, and tunnels.
Guarino and his team work on a full-scale structural model made of steel beams and girders connected by bolts. They tap the structure with a hammer, causing it to vibrate. The sounds made by the vibrating bolts are recorded by an electronic stethoscope, similar in design to the stethoscopes used by doctors. Then the engineers unscrew the bolts a bit, tap the structure again, and listen for changes in the sounds. "Any slight relaxation in a joint can change the way it vibrates," says Guarino.
Using a pattern detection technique called the continuous wavelet transform, the team can pick out which ranges of frequencies change the most. Their results suggest that the signatures of unscrewing may be found in certain mid-to-high frequencies. During the talk, Guarino will be explaining and playing these sounds, available for use by the press.
The research is still in the preliminary stages of lab testing. But Guarino hopes to eventually take it into the field to check for bolts that are vibrating loose or degrading through exposure to the elements. "If we're successful, this could lead to implanting permanent, inexpensive accelerometers that could monitor joints continuously," says Guarino.
The talk "Acoustic detection of bolt detorquing in structures" (3a5A8) by Joe Guarino is at 10:30 a.m. on Wednesday, May 20.
5) MUSIC WORDS
In the world of wine tasting, people often use evocative words, such as "fruity" or "chalky," to convert a taste sensation into everyday language. Can one do the same thing for a piece of music? What are the words most used in describing an aural experience? MIT scientist Mihir Sarkar asked more than 800 people to listen to a battery of 64 sounds and then to match them up with a selection of 62 words to describe the quality or timbre of the sounds. Some of the favorite words they chose included "resonant," "metallic," "warm," and "thin." Surprisingly, non-musicians generally chose the same words as musically-trained persons. Sarkar says that one possible application for these studies would be in designing audio post-processing software. For example, a sound engineer could tell the computer, "Make this sound 'brighter'," and that sound track would be made "brighter." (http://web.media.mit.edu/~mihir/projects/sound_design.html).
The talk "The effect of musical experience on describing sounds with everyday words" (4aMU2) is at 9:15 a.m. on Thursday, May 21.
6) THE PECULIAR HYENA'S LAUGH
To human ears, the laughs of individual hyenas in a pack all sound the same: high-pitched and staccato, eerie and maniacal. But every hyena makes a different call that encodes information about its age and status in the pack, according to behavioral neurologists from the University of California, Berkeley and the Université de Saint-Etienne, France. They have developed a way to identify a hyena by picking out specific features of its giggle.
The hyena does not laugh when it is having a good time. Rather, field biologists have noticed that hyenas make the sound when competing for food. The giggle is a sign of frustration, a call made by a subordinate animal when dominated by one of its peers.
To find meaning in the giggle, Nicolas Mathevon and his colleagues analyzed sounds made by 17 spotted hyenas kept in captivity. They developed an algorithm that can successfully identity an individual in the pack about half the time, by looking at the timbre and quality of a single note in its giggle. "It's like telling singers apart by having them sing one note and listening to the quality of that note," says Mathevon. Their analysis also shows that the pitch of the giggle drops for older animals, and the giggles of animals that tend to be dominant are less variable. The next step will be to play different kinds of giggles to hyenas and test how the animals respond.
The talk "The hyena's laugh as a multi-informative signal" (4pAB3) by Nicolas Mathevon is at 3:30 p.m. on Thursday, May 21.
7) SUPPLE WAVES IN CHEESE AND SKIN
When acoustic waves propagate through a given material, the ocean for instance, the sound waves respond to the properties of the fluid. Scientists can use these responses to probe the characteristics of the medium -- the ocean or the atmosphere, for instance -- and one particularly powerful way of doing this employs a technique called "time reversal." In time reversal, signals are played backwards to cancel out interfering noise. The technique is used in astronomy to remove atmospheric blurring and in medical imaging to focus ultrasonic beams. It is also being developed for underwater communication in the ocean.
Now a group of scientists in Grenoble, France and Montevideo, Uruguay have developed a method based on time reversal that can reveal the characteristics of soft solids. In a pair of presentations, the team will report how they measure the elastic properties of soft solids by using surface or bulk acoustic waves. This allows them to characterize the tenderness of beef and monitor the ripening process of soft cheese.
Their approach is a promising low cost technique for future applications in food production and other industries. In medicine, for instance, measuring shear elasticity is a hot topic in neuromusclular disease, and it may be relevant to diseases in the brain or for monitoring changes in moving organs, such as the heart. Their method can also allow determination of the human skin elasticity.
The talk "Tissue shear elasticity assessment using time reversal" (1pBB9) by Thomas Gallot et al is at 3:35 p.m. on Monday, May 18 in room Pavilion East. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa134.html
The talk "Time-reversal Rayleigh wave for soft solid characterization" (1pBB10) by Javier Brum et al is at 3:50 p.m. on Monday, May 18 in room Pavilion East. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa135.html
8) HOW THE BAGPIPE GOT ITS VOICES
Few instruments produce as distinct a sound as the bagpipe. Played for centuries in Scotland, the Middle East, and across Europe, the piped windbag combines a moving melody with one more constant drones. Three talks on Wednesday, May 20 will feature experts on the instrument, who will discuss both the evolution and unusual acoustics of its sound. Paul Wheeler of Utah State University will provide an introduction to and taxonomy of bagpipes from the around the world. R. Dean Ayers of Southern Oregon University will consider the acoustics of the bagpipe's "drone," the simple monotone pitch produced by a cylindrical pipe. And Stanley Cheyne of Hampden-Sydney College will analyze how the Great Highland Bagpipe's drone meshes with the sound waves of the "chanter," the pipes on which the melody is played.
The talk "An Introduction to Bagpipes of the World" (3Pmua1) by Paul Wheeler is at 1:05 p.m. on Wednesday, May 20.
The talk "A brief history and acoustical analysis of the Great Highland Bagpipe" (3Pmua2) by Stanley Cheyne is at 1:30 p.m. on Wednesday, May 20. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa730.html
The talk "Tuning and tone quality of bagpipe drones" (3Pmua3) by R. Dean Ayers et al is at 2:00 p.m. on Wednesday, May 20.
9) EXPLODING BUBBLES TRIM THE PROSTATE
In the traditional treatment for prostate growths, a rigid instrument is inserted through the penis and used to scrape away cells lining the walnut-sized gland. Urologist William Roberts and a team at the University of Michigan, Ann Arbor, are developing a less invasive way to remove tissue using focused pulses of ultrasound. Their technique, histotripsy, has now been used to safely trim the interiors of aging prostates in the body.
Unlike other therapeutic ultrasound technologies in development, which create heat to boil pathogenic tissue, histotripsy mechanically breaks apart tissue with shorter, strong pulses of ultrasound. These pulses create tiny bubbles out of dissolved gas in prostate tissue. As the bubbles violently collapse, they release tiny shock waves, a phenomena called acoustic cavitation. Over tens of thousands of pulses, the combined force of these cavitations liquefies nearby tissue into slurry that is eliminated through the urine. This tissue excavation can be monitored and targeted in real time with acoustic imaging.
"Historically, no one believed that cavitation could be controlled like this. We're the only group doing this kind of work," says Roberts. His team used the technique to dissolve marble-sized chunks of cells in the walls of prostates. Side effects common in traditional prostrate treatments -- bleeding and inflammation -- were minimal after histotripsy treatment, as were signs of discomfort. Roberts hopes to develop histotripsy into a clinical treatment for early-stage cancer and enlarged prostate (BPH).
The talk "Histotripsy: Urologic applications" (3pBB3) by William Roberts is at 1:15 p.m. on Wednesday, May 20, 2009.
10) REVERSING TIME TO SPOT CRACKS IN GAS PIPES
Checking natural gas pipelines for wear and tear costs big bucks. Sections of pipe must be manually exhumed to be tested for cracks or corrosion with acoustic or magnetic scanners. Nicholas O'Donoughue of Carnegie Mellon University and colleagues are developing a way to monitor pipes continuously and remotely using embedded, low-power ultrasonic detectors. His team will present the latest simulations and experimental evidence showing the detectors are feasible.
Detecting problems in buried pipes using ultrasound is tricky because they tend to disperse broadcast waves of sound. But this scattering is an ideal property for a technique called time reversal, where rich patterns created by dispersion can be analyzed to spot changes in a material. O'Donoughue's idea is send a wideband ultrasonic signal from one detector to another, through the walls of the pipe. When the signal bounces back and retraces its steps to the first detector, any structural imperfections show up as a disturbance in the combination of forwards and backwards waves. "If there is a crack or corrosion, the waves will not retrace their steps," says O'Donoughue.
The team is designing rings of these sensors to attach to the outside of pipes. The idea is to space out the rings, each which will eventually contain between four and eight sensors, 200 meters apart from each other. Simulations suggest a single sensor in each ring doubles the power output, that multiple sensors should further improve the performance, and that this configuration can detect a change in mass. The data from preliminary experiments show that time reversal should work in buried pipes.
The talk "Detection of structural faults in pipelines with time reversal" (3aSA7) by Nicholas O'Donoughue et al is at 10:15 a.m. on Wednesday, May 20, 2009. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa664.html
11) LASER MAKES BIG BANGS UNDERWATER
Technologies that use underwater acoustics -- for sonar, communications, or navigation -- often require a piece of hardware in the water to create sound remotely. Physicist Ted Jones and his team at the U.S. Naval Research Laboratory in Washington, DC, are working on ways to use flashes of laser light instead. These lasers travel through air and water to generate an underwater explosion of sound at a remote location without the need for extra hardware. They will present their latest experimental data testing laser acoustics in a bubbly salt water tank and comparing two types of lasers.
The conversion of light into sound is possible because certain kinds of light pulses will self-compress, superheating a small volume of water. This optical compression happens because the intense laser light changes the properties of water so that it acts like a focusing lens and because slightly different colors of the laser travel at different speeds in water. The resulting explosion of steam it creates can generate a 210 decibel pulse of sound.
Currently, Jones is tailoring two different kinds of visible and infrared lasers to produce these pulses, which could eventually be used to encode information. The NRL group has created broadband laser pulses that can travel up to 20 meters through water to create acoustic pulses at precise distances. The laser light can also travel hundreds of meters through clear air, so one potential application is airplane-to-submarine communication. Acoustic reflections from the pings they produce could also be monitored to gather information about underwater environments, from detecting mines to mapping the bottom of the ocean floor.
The talk "Intense underwater laser acoustic source for Navy applications" (2aEA-7) by Ted Jones is at 10:30 a.m. on Tuesday, May 19.
12) ICELANDIC SAGA: RETURN OF THE RIGHT WHALE
The North Atlantic right whale, with only about 300-350 animals known to exist, used to inhabit the Cape Farewell Ground, which lies between southwest Iceland and Greenland. In the 1800s they were heavily hunted in this area and haven't been seen much there since. Recently acoustic sensors stationed in this channel have discovered a return of right whales to their old territory. According to David Mellinger at the Oregon State University, the right whales were located and identified by their distinctive "up calls," which are part of the animals' extensive vocalization repertory. Owing to the low number of right whales, the return of the animals to a former whaling ground is an exciting discovery, says Mellinger.
The talk "Acoustical rediscovery of right whales in a former whaling area, the Cape Farewell Ground, between Greenland and Iceland" (3aAB9) is at 10:45 a.m. on Wednesday, May 20. Abstract: http://asa.aip.org/web2/asa/abstracts/search.may09/asa583.html
13) CLOGGED PIPES MAKE A SPECIAL SOUND
One way to find a clog under a sink is to take on the dirty job of dismantling the pipes. Now mathematician Alex Tolstoy, of ATolstoy Sciences in the United States, and colleagues at the University of Bradford in the United Kingdom have developed a cleaner way that hears where a blockage is located, using a technique pioneered in underwater acoustics. With further development, the method could be used to remotely track down problems in unpleasant areas like sewer lines.
The group built a device that -- like the echolocation used by bats and dolphins -- sends out high-pitched frequencies and listens to the sounds that bounce back. The listening device first records the profile of reflected sound coming back from an empty pipe. When the pipe is blocked, this sound profile changes. Using a signal-processing technique called matched-field processing, Tolstoy picks out the more important changes and calculates how long these frequencies took to bounce back to the two microphones on the device. This time indicates how far along in the pipe the clog is located.
The team has tested the device on a variety of different kinds of pipes -- concrete, PVC, clay -- blocked up with a different sizes and amounts of sandbags and bricks. The technique is not affected by twists and turns in the pipes. For the moment, only empty, air-filled pipes have been tested. In theory, the technique should work just as well with fluid-filled pipes, though further work would be needed to compensate for the dynamics of the fluid.
The talk "Detecting and localizing pipe changes via matched field processing" (4aSP7) by Alex Tolstoy et al is at 10:45 on Thursday, May 21.
14) LISTENING TO LEVEES
Many dams are made of earthen substances such as soil, a granular material with tiny constituent particles that interact amongst themselves. When water is also present in soil, capillary (suction) forces are at work too. Sound waves can be sent into soil to measure properties such as porosity, temperature, and water content. This kind of testing is particularly important when an upper layer of soil is dry and an underlying layer wet. Then the upper layer becomes unstable and landslides can occur.
Zhiqu Lu of the University of Mississippi will report on a newer, higher-precision device, one employing laser sensing of ground vibrations, for the monitoring of levees and dams using sound waves in a non-invasive way down to depths of several meters. (Paper 1pPA2)
The talk "Effects of soil water potential and moisture content on sound speed" (1pPA1) by Zhiqu Lu et al is at 1:30 p.m. on Monday, May 18.