While there is great interest in studying the structure of Venus because it is believed to be similar to Earth, there are no direct seismic measurements on Venus. This is because the Venus surface temperature is too hot for electronics, but conditions are milder in the middle of the Venus atmosphere. This has motivated interest in studying seismic activity using low frequency sound measurements on high altitude balloons. Recently, this method was demonstrated on Earth with weak earthquakes being detected from balloons flying at twice the altitude of commercial airplanes. Video 1 shows a balloon launch for these test flights. Due to the denser atmosphere on Venus, the coupling between the Venus-quake and the sound waves should be much greater, which will make the sound louder on Venus. However, the higher density atmosphere combined with vertical changes in wind speed is also likely to increase the amount of wind noise on these sensor. Thus development of a new technology to reduce wind noise on a high altitude balloon is needed.
Video 1. Video of a balloon launch during the summer of 2021. Video courtesy of Jamey Jacob.
Several different designs were proposed and ground tested to identify potential materials for compact windscreens. The testing included a long-term deployment outdoors so that the sensors would be exposed to a wide range of wind speeds and conditions. Separately, the sensors were exposed to controlled low-frequency sounds to test if the windscreens were also reducing the loudness of the signals of interest. All of the designs showed significant reduction in wind noise with minimal reduction in the controlled sounds, but one design in particular outperformed the others. This design uses a canvas fabric on the outside of a box as shown in the Figure 1 combined with a dense foam material on the inside.
Figure 1. Picture of balloon carrying the low frequency sound sensors. Compared an early design to no windscreen with this flight. Image courtesy of Brian Elbing.
The next step is to fly this windscreen on a high altitude balloon, especially on windier days and with a long flight line to increase the amount of wind that the sensors will experience. The wind direction at the float altitude of these balloons will change in May and then rapidly increase, which this will be the target window to test this new design.
Stanford University CCRMA / Music Stanford, CA 94305 United States
Ge Wang Stanford University
Michael Mulshine Stanford University
Jack Atherton Stanford University
Popular version of 1aCA1 – What would a Webchuck Chuck? Presented at the 184 ASA Meeting Read the abstract at https://doi.org/10.1121/10.0018058
Take all of computer music, advances in programming digital sound, the web and web browsers and create an enjoyable playground for sound exploration. That’s Webchuck. Webchuck is a new platform for real-time web-based music synthesis. What would it chuck? Primarily, musical and artistic projects in the form of webapps featuring real-time sound generation. For example, The Metered Tide video below is a composition for electric cellist and the tides of San Francisco Bay. A Webchuck webapp produces a backing track that plays in a mobile phone browser as shown in the second video
Video 1: The Metered Tide
The backing track plays a sonification of a century’s worth of sea level data collected at the location while the musician records the live session. Webchuck has fulfilled a long-sought promise for accessible music making and simplicity of experimentation.
Video 2: The Metered Tide with backing track
Example webapps from this new Webchuck critter are popping up rapidly and a growing body of musicians and students enjoy how they are able to produce music easily and on any system. New projects are fun to program and can be made to appear anywhere. Sharing work and adapting prior examples is a breeze. New webapps are created by programming in the Chuck musical programming language and can be extended with JavaScript for open-ended possibilities.
Webchuck is deeply rooted in the computer music field. Scientists and engineers enjoy the precision that comes with its parent language, Chuck, and the ease with which large-scale audio programs can be designed for real-time computation within the browser. Similar capabilities in the past have relied on special purpose apps requiring installation (often proprietary). Webchuck is open source, runs everywhere a browser does and newly-spawned webapps are available as freely-shared links. Like in any browser application, interactive graphics and interface objects (sliders, buttons, lists of items, etc.) can be included. Live coding is the most common way of using Webchuck, developing a program by hearing changes as they are made. Rapid prototyping in sound has been made possible by the Web Audio API browser standard and Webchuck combines this with Chuck’s ease of abstraction so that programmers can build up from low-level details to higer-level features.
Combining the expressive music programming power of Chuck with the ubiquity of web browsers is a game changer that researchers have observed in recent teaching experiences. What could a Webchuck chuck? Literally everything that has been done before in computer music and then some.
Naval Undersea Warfare Center Division, Keyport, Test and Evaluation Department., Keyport, Washington, 98345, United States
Popular version of 4aPAa12 – Considerations of undersea exploration of an extraterrestrial ocean
Presented at the 184 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0018848
As we venture out beyond our home planet to explore our neighbors in our solar system, we have encountered the most extreme environments we could have imagined that provide some of greatest engineering challenges. Probes and landers have measured and experienced dangerous temperatures, atmospheres, and surfaces that would be deadly for human exploration. However, no extraterrestrial ocean environments have been studied beyond observation, which are the mostly unexplored portions of our planet. Remarkably, pass-by planetary probes have found the possible existence of oceans on two of Jupiter’s moons Europa and Ganymede and the existence of a potential ocean, as well as lakes and rivers on Titan, a moon of Saturn. Jupiter’s moon Europa could have a saltwater ocean that could be between 60 and 90 miles deep, covered in up to 15 miles of ice. The deepest point in Earth’s Ocean is a maximum of about 7.5 miles for comparison about 10 to 15 times shallower. Those extreme pressures experienced at that depth would be difficult to withstand with current technology and acoustic propagation could potentially behave differently also. At those pressures, water might not freeze above 8°F (~260 K), causing liquid water at temperatures not seen in our oceans. The effects of this would be found in the speed of sound, which are shown in Figure 1 through a creative and imaginative modelling scheme numerically simulated. The methods used were a mixture of using Earth data with predictive speculation, and physical intuition.
Figure 1. Imaginative scientific freedom determining the speed of sound in the deep ocean on Europa beneath a 30 km ice sheet. The water stays liquid down to potentially 260 K (8 degrees F), heated by currently an unknown mechanism probably related to Jupiter’s gravitational pull.
On Titan, a moon of Saturn, there are lakes and rivers of hydrocarbons like Methane and Ethane. For these compounds to be liquid, the temperature would have to be about -297°F. We know how sound interacts with Methane on Earth, because it is a gas for our conditions, but we would have to get it to cryogenic temperatures to study the acoustics as a liquid. We would have to build systems that could swim around in such temperatures to explore what is underneath. At liquid water temperatures, like potentially some of the extraterrestrial oceans predicted to exist, conditions may still be amenable to life. But to discover that life will require independent systems, making measurements and gathering information for humans to see through the eyes of our technology. The drive to explore extreme ocean environments could provide evidence of life beyond Earth, since where there is water, life is possible.
Helping Acoustic Concepts Resonate with Students #ASA183
An experimental music piece can help teach concepts of resonance in a more interesting way.
Media Contact: Ashley Piccone AIP Media 301-209-3090 media@aip.org
NASHVILLE, Tenn., Dec. 7, 2022 – “I am sitting in a room, different from the one you are in now.” With these words, Alvin Lucier begins a fascinating recording where his voice warps and becomes indistinguishable over time — solely because of how sound reflects in the room. For physics students, this audio can be used to reveal details of the surrounding room and teach important lessons about acoustic resonance.
When a sound is made and recorded in a room, then replayed and rerecorded repeatedly, it becomes distorted. Frequencies that correspond to the room itself are emphasized. Credit: Andy Piacsek
Andy Piacsek, of Central Washington University, will discuss how he employs Lucier’s project in the classroom during his talk, “Students are sitting in a room.” The presentation will take place on Dec. 7 at 12:10 p.m. Eastern U.S. in the Lionel room, as part of the 183rd Meeting of the Acoustical Society of America running Dec. 5-9 at the Grand Hyatt Nashville Hotel.
To create this interesting audio, Lucier recorded seventy seconds of speech in a room, played it back over a speaker, and repeatedly rerecorded the result. Eventually, the feedback overwhelms the original recording, and the words are replaced by a collection of distorted frequencies.
In the first iteration of Lucier’s recording, his speech contains the typical range of sound frequencies that make up a human voice. When sounds at most frequencies bounce off the walls in the room, they get jumbled together and eventually fade out. But some frequencies ‘fit’ perfectly in the distances between opposite walls, and these frequencies resonate and grow louder with each recorded iteration.
“Each pair of walls has a set of natural frequencies,” said Piacsek. “By analyzing the frequencies that make up the recording, especially in the later stages, students can determine which frequencies are resonances of the room. The tricky part is figuring out which frequencies go with which pair of walls. This is a bit of a puzzle… and puzzles are fun!”
After identifying the resonant frequencies, students can apply their knowledge of physics to calculate the distance between pairs of walls, and therefore the size of the room Lucier used for his recording. More advanced students can try to make a version of the recording in their own rooms and see if their calculations match their measured room dimensions.
“At the introductory level, especially, many students come to a science class with the notion that science is dry and abstract, not something they identify with,” said Piacsek. “When they see how their classroom learning applies to scenarios they can relate to, it becomes less abstract and they remember it better.”
ASA PRESS ROOM In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.
LAY LANGUAGE PAPERS ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are 300 to 500 word summaries of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at https://acoustics.org/lay-language-papers/.
PRESS REGISTRATION ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the meeting or virtual press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
Martian Dust Devil Analogues in the Mojave Desert #ASA183
Identifying and characterizing dust devils on Earth can inform their formation and lifecycles on Mars, where dust storms can make or break missions.
Media Contact: Ashley Piccone AIP Media 301-209-3090 media@aip.org
NASHVILLE, Tenn., Dec. 7, 2022 – In the Mojave Desert, the sun beats down on the ground and makes pockets of low pressure. Cool air rushes into these areas, where it warms and rises, creating vortices that pick up dust. These types of dust devils aren’t limited to Earth: they are found on Mars at sizes reaching 1,600 meters in diameter.
A dust devil in the Arizona desert (left) and on Mars (right). Credit: NASA/U. of Michigan
Dust devils could play a large role in the Martian climate, and they are crucial to understand during missions to the red planet. Louis Urtecho of NASA JPL and the California Institute of Technology will describe efforts to identify the vortices using data from the Mojave Desert in his presentation, “Automated detection of dust-devil-induced pressure signatures.” The talk will take place on Dec. 7 at 10:40 a.m. Eastern U.S. in the Golden Pass room, as part of the 183rd Meeting of the Acoustical Society of America running Dec. 5- 9 at the Grand Hyatt Nashville Hotel.
“The abundance of dust devils on Mars could have implications for the lifetimes of many missions. In fact, dust devils have already played a role in past missions,” said Urtecho. “Opportunity and Spirit rovers’ lives were extended because friendly dust devils blew dust off their solar panels. But Opportunity eventually succumbed to a global dust storm on Mars, showing the importance of dust loading in the atmosphere.”
It is difficult to find and study dust devils on Mars, so Urtecho and his team hope to study them on Earth, then extend the analysis to scale for the different atmosphere. Based on microbarometer data from the Mojave Desert, they built an algorithm to look for the pressure activity indicative of a dust devil. The vortices have a distinct drop in pressure near their centers, and their pressure fluctuates to look like an electrocardiogram (EKG) signal over time.
“The hope is that with our dust devil detector we will be able to learn more about the formation characteristics of convective vortices and how they move across various landscapes,” said Urtecho. “This will improve the accuracy of Martian weather models, which has a direct impact not only in understanding dust cycles on Mars and the role they have played in its evolution, but also the operation of future robotic and possibly crewed missions.”
ASA PRESS ROOM In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.
LAY LANGUAGE PAPERS ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are 300 to 500 word summaries of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at https://acoustics.org/lay-language-papers/.
PRESS REGISTRATION ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the meeting or virtual press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
Christopher Kube – kube@psu.edu
Twitter: @_chriskube
Penn State University, 212 Earth and Engineering Sciences Bldg, University Park, PA, 16802, United States
Tao Sun, University of Virginia
Samuel Clark, Advanced Photon Source, Twitter: @advancedphoton
Find the authors on LinkedIn:
www.linkedin.com/in/chriskube
www.linkedin.com/in/suntao
Popular version of 3pID2-Acoustics for in-process melt pool monitoring during metal additive manufacturing, presented at the 183rd ASA Meeting.
3D printed or additively manufactured (AM) metal parts are disrupting the status quo in a variety of industries including defense, transportation, energy, and space exploration. Engineers now design and produce customizable parts unimaginable only a decade ago. New geometrical or part shape freedom inherent to AM has already led to part performance often beyond traditionally manufactured counterparts. In the years to come, another revolutionary performance jump is expected by enabling the AM process to control the grain layout and structural features on the microscopic scale. Grains are the building blocks of metal parts that dictate many of the performance metrics associated with the descriptors of bigger, faster, and stronger.
The second performance revolution of AM metal parts requires uncovering new knowledge in the complicated physics present during the AM process. 3D printed metals are born from an energy source such as a laser or electron beam to selectively melt feedstock material at microscopic locations dictated by the computerized part drawing. Melted locations temporarily form liquid metal melt pools that solidify after the energy source moves to another location. Resulting grain structure and pore/defect formation strongly depends on how the melt pool cools and solidifies.
Over the past five years, high-energy X-rays only available at particle accelerators are used for direct real-time visualization of AM melt pool dynamics and solidification. Figure 1 shows an example X-ray frame, which captured a laser-generated melt pool moving in a single direction with a speed of 800 mm/ms.
This situation mimics the laser and melt pool movement found during 3D printing metal parts. Being able to directly observe melt pool behavior has led to new and improved understanding of the underlying physics. Unfortunately, experiments at such X-ray sources is difficult to ascertain because of extremely high demand across the sciences. Additionally, the measurement technique relegated to high-energy X-ray sources is not transferrable to metal 3D printers that exist in normal industrial settings. For these reasons, ultrasonics are being explored as a melt pool monitoring technology that can be deployed within real 3D printers.
Ultrasound is commonly used for imaging and detecting features inside of solid materials. For example, ultrasound is applied in medical settings during pregnancy or for diagnostics. Application of ultrasound for melt pool monitoring is made possible because of the tendency of ultrasound to scatter from the melt pool’s solid/liquid boundary. The development of the technique is being supported alongside X-ray imaging at the Advanced Photon Source at Argonne National Laboratory. X-ray imaging is providing the extremely important ground truth melt pool behavior allowing for easy interpretation of the ultrasonic response. In Figure 1, the ultrasonic response from the exact same melt pool given in the X-ray video is being shown for two different sensors. As the melt pool enters the field of view of the ultrasonic sensors (see online video), features in the ultrasound response confirms their sensitivity to the melt pool.
In this research, high-energy X-rays are being used to develop the ultrasonic technique and technology. In the coming year, the knowledge developed will be leveraged such that ultrasound can be applied on its own for melt pool monitoring in real metal 3D printers. Currently, no existing technology can capture the highly dynamic melt pool behavior through the depth of the part or substrate.
Practical benefits and value of melt pool monitoring within 3D printers are significant. Ultrasound can provide a quick check to determine the optimal laser power and speed combinations toward accelerated determination of process parameters. Currently, determination of the optimal process parameters requires destructive postmortem microscopy techniques that are extremely costly, time-consuming (sometimes more than a year), and wasteful. Ultrasound has the potential to reduce these factors by an order of magnitude. Furthermore, metal 3D printing processes are highly variable over many months, across different machines, and even when using feedstock powder from different suppliers. Ultrasonic melt pool monitoring can provide period checks to assure variability is minimized.
Figure 1. Imaginative scientific freedom determining the speed of sound in the deep ocean on Europa beneath a 30 km ice sheet. The water stays liquid down to potentially 260 K (8 degrees F), heated by currently an unknown mechanism probably related to Jupiter’s gravitational pull.
