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.
Multimedia Systems, The Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Pomorskie, 80-233, Poland
Jozef Kotus – Multimedia Systems, The Faculty of Electronics, Telecommunications and Informatics,
Grzegorz Szwoch – Multimedia Systems, The Faculty of Electronics, Telecommunications and Informatics],
Bozena Kostek – Audio Acoustics Lab., Gdansk Univ. of Technology, Gdansk, Poland
Popular version of 3pPAb1-Assessment of road surface state with acoustic vector sensor, presented at the 183rd ASA Meeting.
Have you ever listened to the sound of road vehicles passing by? Perhaps you’ve noticed that the sound differs depending on whether the road surface is dry or wet (for example, after the rain). This observation is the basis of the presented algorithm that assesses the road surface state using sound analysis.
Listen to the sound of a car moving on a dry road.
And this is the sound of a car on a wet road.
A wet road surface not only sounds different, but it also affects road safety for drivers and pedestrians. Knowing the state of the road (dry/wet), it is possible to notify the drivers about dangerous road conditions, for example, using signs displayed on the road.
There are various methods of assessing the road surface. For example, there are optical (laser) sensors, but they are expensive. Therefore, we have decided to develop an acoustic sensor that ‘listens” to the sound of vehicles moving along the road and determines whether the surface is dry or wet.
The task may seem simple, but we must remember that the sensor records the sound of road vehicles and other environmental sounds (people speaking, aircraft, animals, etc.). Therefore, instead of a single microphone, we use a special acoustic sensor built from six miniature digital microphones mounted on a small cube (10 mm side length). With this sensor, we can select sounds incoming from the road, ignoring sounds from other directions, and also detect the direction in which a vehicle moves.
Since the sound of road vehicles moving on a dry and wet surface differ, performing frequency analysis of the vehicle sounds is recommended.
The figures below present how the sound spectrum changes in time when a vehicle moves on a dry surface (left figure) and a wet surface (right figure). It is evident that in the case of a damp surface, the spectrum is expanded towards higher frequencies (the upper part of the plot) compared with the dry surface plot. Colors on the plot represent the direction of arrival of sound generated by vehicle passing by (the angle in degrees). You can observe how the vehicles moved in relation to the sensor.
Plots of the sound spectrum for cars moving on a dry road (left) and a wet road (right). Color denotes the sound source azimuth. In both cases, two vehicles moving in opposite directions were observed.
In our algorithm, we have developed a parameter that describes the amount of water on the road. The parameter value is low for a dry surface. However, as the road surface becomes increasingly wet during rainfall, the parameter value becomes more extensive.
The results obtained from our algorithm were verified by comparing them with data from a professional road surface sensor that measures the thickness of a water layer on the road using a laser beam (VAISALA Remote Road Surface State Sensor DSC111). The plot below shows the results from analyzing sounds recorded from 1200 road vehicles passing by the sensor, compared with data obtained from the reference sensor. The data were obtained from a continuous 6-hour observation period, starting from a dry surface, then observing rainfall until the road surface had dried.
A surface state measure calculated with the proposed algorithm and obtained from the reference device
As one can see, the results obtained from our algorithm are consistent with data from the professional device. Therefore, the results are promising, and the cheap sensor is easy to install at multiple points within a road network. Hence, it makes the proposed solution an attractive method of road condition assessment for intelligent road management systems.
Infrasound pulses from munitions plant explosions used to study gravity waves, atmospheric events
Media Contact: Larry Frum AIP Media 301-209-3090 media@aip.org
DENVER, May 25, 2022 – Infrasound waves can probe some of the most complex weather patterns hidden to normal observations, but finding a powerful enough source of infrasound waves can be a challenge unless there is a munitions factory nearby.
During the 182nd Meeting of the Acoustical Society of America, Stephen Arrowsmith, from Southern Methodist University, will discuss a method for using infrasound pulses from detonated munitions to probe atmospheric phenomena. His presentation, “The use of infrasound from repeating explosion sequences in Oklahoma to probe the atmosphere,” will take place May 25 at 10:55 a.m. Eastern U.S. at the Sheraton Denver Downtown Hotel.
Infrasound waves are acoustic waves at frequencies too low for humans to hear, but they can be invaluable for studying atmospheric phenomena. One example is gravity waves, which are small-scale waves in the atmosphere driven by buoyancy. These waves are small and transient, making them challenging to study with traditional methods. Infrasound waves have the speed and resolution to track those gravity waves.
“The sound that we record propagates upward into the atmosphere and is refracted back down to the ground,” said Arrowsmith. “The information they provide on the upper atmosphere can tell us about the winds aloft, and these can affect the weather at the ground.”
These infrasound waves need to be strong enough to reach the atmosphere and bounce back, which requires a sizeable source. Fortunately for Arrowsmith, an Oklahoma munitions factory routinely sets off large explosions multiple times per day. He and his team set up detectors in the area around the factory to measure infrasound reflections from the troposphere and stratosphere.
They were able to use the data to study short-term atmospheric fluctuations and tie those fluctuations to gravity waves and other events. They then compared their data across multiple days to study longer-term trends and compare those to meteorological models.
Arrowsmith intends this result to serve as a demonstration of the power of infrasound to probe the atmosphere and study some of its more elusive elements. He hopes infrasound could one day be used as a tool to better understand and predict weather patterns.
WORLDWIDE PRESS ROOM In the coming weeks, ASA’s Worldwide Press Room will be updated with additional tips on dozens of newsworthy stories and with lay language papers, which are 300 to 500 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio and video. You can visit the site during the meeting at https://acoustics.org/world-wide-press-room/.
PRESS REGISTRATION We will grant free registration to credentialed journalists and professional freelance journalists. If you are a reporter and would like to attend, contact AIP Media Services at media@aip.org. For urgent requests, staff at media@aip.org 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/.
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.
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.
Plots of the sound spectrum for cars moving on a dry road (left) and a wet road (right). Color denotes the sound source azimuth. In both cases, two vehicles moving in opposite directions were observed.
A surface state measure calculated with the proposed algorithm and obtained from the reference device