Catch and Release Can Give Sea Turtles the Bends #ASA186

Veterinarians team up with fishers to evaluate the health of accidentally caught sea turtles.

Media Contact:
AIP Media
301-209-3090
media@aip.org

OTTAWA, Ontario, May 13, 2024 – Six out of seven sea turtle species are endangered, and humans are primarily responsible. Commercial fishing activities are the largest human-caused disturbance to sea turtles due to accidental capture.

Fishers are typically unaware if a sea turtle is caught in their net until its completely pulled out of the water. However, releasing sea turtles without veterinary evaluations can be harmful. When accidentally caught, the turtles’ normal diving processes are interrupted, which can cause abnormal gas in their organs, gas emboli, to form. Veterinarians around the globe are working to understand the possible consequences of this pathology and determine the best treatment for turtles depending on when they surface. Here, they used ultrasound imaging to get a closer look at sea turtles’ bodies in realtime, focusing on the heart, liver, and kidney.

A sea turtle getting an ultrasound at Oceanogràfic as part of a veterinary procedure. (Photo taken by Katherine Eltz during her visit there to learn more about how this type of data is acquired for veterinary purposes)

Katherine Eltz, a first-year doctoral student at the University of North Carolina at Chapel Hill, determined that there are ways to differentiate gas levels over time in sea turtles. Eltz, whose home laboratory focuses on ultrasound imaging for decompression sickness mitigation in humans, collaborated with veterinarians who measured gas emboli in turtles in real time on fishing boats. She will present her work Monday, May 13, at 4:00 p.m. EDT as part of a joint meeting of the Acoustical Society of America and the Canadian Acoustical Association, running May 13-17 at the Shaw Centre located in downtown Ottawa, Ontario, Canada.

“Veterinarians can examine whole-body MRI or X-ray scans and find specific bubbles in a variety of different organs,” said Eltz. “The benefit of ultrasound is that we can see bubbles flowing through vessels or stationary in tissues. The portability of ultrasound means that it can be brought onto fishing boats, which we took advantage of to collect half of the data used in this project.”

Her collaborators from the Oceanogràfic Foundation were the first to report decompression sickness in turtles. Eltz examined ultrasound data collected from sea turtles found off the coast of Brazil, Italy, and Spain, though this issue is found in sea turtles worldwide. The data collection from Eltz’s collaborators at Oceanogràfic comes from veterinarians who joined fishers off the coasts of these countries and imaged the turtles immediately to monitor their bubbles after surfacing.

Eltz’s results come from two experimental groups with different circumstances regarding time and gas severity. The brightness from the ultrasounds taken from the groups is a valuable quantitative metric to separate each ultrasound by grade. These findings can help veterinarians better treat sea turtles presenting with gas embolism. Ultrasound brightness could become a quantitative metric for veterinarians to determine which turtles need hyperbaric oxygen treatment and which can be released.

“The largest task still at hand is to work towards standardizing the acquisition of the ultrasound data collected for this project,” said Eltz. “Now, I can work with veterinarians to help adjust their methods, including improved image processing to standardize the data in post-processing.”

With a rich dataset from Oceanogràfic at her disposal, Eltz hopes to examine other possible factors that may be related to gas severity. These insights all help lead to better prediction of the outcomes for bycaught sea turtles.

———————– MORE MEETING INFORMATION ———————–
Main Meeting Website: https://acousticalsociety.org/ottawa/
Technical Program: https://eppro02.ativ.me/src/EventPilot/php/express/web/planner.php?id=ASASPRING24

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 summaries (300-500 words) 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 in-person 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 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/.

ABOUT THE CANADIAN ACOUSTICAL ASSOCIATION/ASSOCIATION CANADIENNE D’ACOUSTIQUE

fosters communication among people working in all areas of acoustics in Canada
promotes the growth and practical application of knowledge in acoustics
encourages education, research, protection of the environment, and employment in acoustics
is an umbrella organization through which general issues in education, employment and research can be addressed at a national and multidisciplinary level

The CAA is a member society of the International Institute of Noise Control Engineering (I-INCE) and the International Commission for Acoustics (ICA), and is an affiliate society of the International Institute of Acoustics and Vibration (IIAV). Visit https://caa-aca.ca/.

Intense Ultrasound Extracts Genetic Info for Less Invasive Cancer Biopsies #ASA186

Upcoming technology can extract cancer biomarkers from cells to enable affordable, noninvasive, and regular cancer screening.

Media Contact:
AIP Media
301-209-3090
media@aip.org

OTTAWA, Ontario, May 13, 2024 – Ultrasound imaging offers a valuable and noninvasive way to find and monitor cancerous tumors. However, much of the most crucial information about a cancer, such as specific cell types and mutations, cannot be learned from imaging and requires invasive and damaging biopsies. One research group developed a way to employ ultrasound to extract this genetic information in a gentler way.

At the University of Alberta, a team led by Roger Zemp explored how intense ultrasound can release biological indicators of disease, or biomarkers, from cells. These biomarkers, like miRNA, mRNA, DNA, or other genetic mutations, can help identify different types of cancer and inform the subsequent therapy. Zemp will present this work Monday, May 13, at 8:30 a.m. EDT as part of a joint meeting of the Acoustical Society of America and the Canadian Acoustical Association, running May 13-17 at the Shaw Centre located in downtown Ottawa, Ontario, Canada.

Ultrasound image of micro-histotripsy liberation of biomarkers in a tumor. Image Credit: Joy Wang and Pradyumna Kedarisetti.

“Ultrasound, at exposure levels higher than is used for imaging, can create tiny pores in cell membranes, which safely reseal,” Zemp said. “This process is known as sonoporation. The pores formed due to sonoporation were previously used to get drugs into cells and tissues. In our case, we care about releasing the contents of cells for diagnostics.”

The ultrasound releases biomarkers from the cells into the bloodstream, increasing their concentration to a level high enough for detection. Using this method, oncologists can detect cancer and monitor its progression or treatment without the need for painful biopsies. Instead, they can use blood samples, which are easier to procure and less expensive.

“Ultrasound can enhance the levels of these genetic and vesicle biomarkers in blood samples by over 100 times,” said Zemp. “We were able to detect panels of tumor-specific mutations, and now epigenetic mutations that were not otherwise detectable in blood samples.”

Not only was this approach successful at detecting biomarkers, but it also boasts a lower price compared to conventional testing.

“We’ve also found that we can conduct ultrasound-aided blood testing to look for circulating tumor cells in blood samples with single-cell sensitivity for the price of a COVID test,” said Zemp. “This is significantly cheaper than the current methods, which cost about $10,000 per test.”

The team also demonstrated the potential for applying intense ultrasound to liquefy small volumes of tissue for biomarker detection. The liquified tissue can be retrieved from blood samples or through fine-needle syringes, a much more comfortable option compared to the damaging core-needle alternative.

More accessible techniques to identify cancer will not only allow for earlier detection and treatment but will also allow medical practitioners to be nimble in their approach. They can establish if certain therapies are working without the risks and expenses often associated with repeated biopsies.

“We hope that our ultrasound technologies will benefit patients by providing clinicians a new kind of molecular readout of cells and tissues with minimal discomfort,” said Zemp.

———————– MORE MEETING INFORMATION ———————–
Main Meeting Website: https://acousticalsociety.org/ottawa/
Technical Program: https://eppro02.ativ.me/src/EventPilot/php/express/web/planner.php?id=ASASPRING24

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 summaries (300-500 words) 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 in-person 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 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/.

ABOUT THE CANADIAN ACOUSTICAL ASSOCIATION/ASSOCIATION CANADIENNE D’ACOUSTIQUE

fosters communication among people working in all areas of acoustics in Canada
promotes the growth and practical application of knowledge in acoustics
encourages education, research, protection of the environment, and employment in acoustics
is an umbrella organization through which general issues in education, employment and research can be addressed at a national and multidisciplinary level

The CAA is a member society of the International Institute of Noise Control Engineering (I-INCE) and the International Commission for Acoustics (ICA), and is an affiliate society of the International Institute of Acoustics and Vibration (IIAV). Visit https://caa-aca.ca/.

What could happen to Earth if we blew up an incoming asteroid?

Brin Bailey – brittanybailey@ucsb.edu

University of California, Santa Barbara, Physics Department, Santa Barbara, CA, 93106, United States

Popular version of 4aPA12 – Acoustic ground effects simulations from asteroid disruption via the ‘Pulverize It’ method
Presented at the 186 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0027433

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Let’s imagine a hypothetical scenario: a new asteroid has just been discovered, on a path straight towards Earth, threatening to hit us in just a few days. What can we do about it?

A new study funded by NASA is trying to answer that question. Pulverize It, or PI for short, is a proposed method for planetary defense–the effort of monitoring and protecting Earth from incoming asteroids. In essence, PI’s plan of attack is to penetrate an incoming asteroid with high-speed, bullet-like projectiles, which would split the asteroid into many smaller fragments (pieces) (Figure 1). PI’s key difference from other planetary defense methods is its versatility. It is designed to work for a wide variety of scenarios, meaning that PI could be used whether an asteroid impact is one year away or one week away (depending on the asteroid’s size and speed).

Figure 1. PI works by penetrating an asteroid with a high-speed, high-density projectile, which rapidly converts a portion of the asteroid’s kinetic energy into heat and shock waves within the rocky material. The heat energy of the impact locally vaporizes and ionizes material near the impact site(s), and the subsequent shock waves damage and fracture the asteroid material as they move and pass (refract) through it.

How is this possible, and how could the asteroid fragments affect us here on Earth? Rather than using momentum transfer–like in methods such as asteroid deflection, as demonstrated by NASA’s recent Double Asteroid Redirection Test (DART) mission–PI utilizes energy transfer to mitigate a threat by disassembling (or breaking apart) an asteroid.

If the asteroid is blown apart while far away from Earth (generally, at least several months before impact), these fragments would miss the planet entirely. This is PI’s preferred mode of operation,as it is always more favorable to keep the action away from us when possible. In a scenario where we have little warning time (a “terminal” scenario), the small asteroid fragments may enter Earth’s atmosphere–but this is part of the plan (Figure 2).

Figure 2. In a short-warning scenario where the asteroid is intercepted and broken up close to Earth (“terminal” scenario), the fragment cloud enters Earth’s atmosphere. Each fragment will burst at high altitude, dispersing the energy of the original asteroid into optical and acoustical ground effects. As the fragments in the cloud spread out, they will enter the atmosphere at different times and in different places, creating spatially and temporally de-correlated shock waves. The spread of the fragment cloud depends on a variety of factors, mainly intercept time (the amount of time between asteroid breakup and ground impact) and fragment disruption velocity (the speed and direction at which fragments move away from the fragment cloud’s center of mass).

Earth’s atmosphere acts as a bulletproof vest, shielding us from harmful ultraviolet radiation, typical space debris, and, in this case, asteroid fragments. As these small rocky pieces enter the atmosphere at very high speeds, air molecules exert large amounts of pressure on them. This puts stress on the rock and causes it to break up. As the fragment’s altitude decreases, the atmosphere’s density increases. This adds heat and increases pressure until the fragment can’t remain intact anymore, causing the fragment to detonate, or “burst.”

When taken together, these bursts can be thought of as a cosmic fireworks show. As each fragment travels through the atmosphere and bursts, it produces a small amount of light (like a shooting star) and pressure (as a shock wave, like a sonic boom). The collection of these optical and acoustical effects, referred to as “ground effects,” work to disperse the energy of the original asteroid over a wide area and over time. In reasonable mitigation scenarios that are appropriate for the incoming asteroid (for example, based on asteroid size or by breaking the asteroid into a very large number of very small pieces), these ground effects result in little to no damage.

In this study, we investigate the acoustical ground effects that PI may produce when blowing apart an incoming asteroid in a “terminal” scenario with little warning. As each fragment enters Earth’s atmosphere and bursts, the pressure released creates a shock wave, carrying energy and creating an audible “boom” for each fragment (a sonic boom). Using custom codes, we simulate the acoustical ground effects for a variety of scenarios that are designed to keep the total pressure output below 3 kPa–the pressure at which residential windows may begin to break–in order to minimize potential damage (Figure 3).

Figure 3. Simulation of the acoustical ground effects from a 50 m diameter asteroid which is broken into 1000 fragments one day before impact. The asteroid is modeled as a spherical rocky body (average density of 2.6 g/cm3) traveling through space at 20 km/s and entering Earth’s atmosphere at an angle of 45°. The fragments move away from each other at an average speed of 1 m/s. The sonic “booms” produced by the fragment bursts are simulated here based upon the arrival of each shock wave at an observer on the ground (indicated by the green dot in the left plot). Note that both plots take into account the constructive interference between shock waves. Left: real-time pressure. Right: maximum pressure, where each pixel displays the highest pressure it has experienced. The dark orange lines, which display higher pressure values, signify areas where two shock waves have overlapped.

Figure 4. Simulation of the acoustical ground effects from an unfragmented (as in, not broken up) 50 m diameter asteroid. The asteroid is modeled as a spherical rocky body (average density of 2.6 g/cm3) traveling through space at 20 km/s and entering Earth’s atmosphere at an angle of 45°. Upon entering and descending through Earth’s atmosphere, the asteroid undergoes a great amount of pressure from air molecules, eventually causing the asteroid to airburst. This burst releases a large amount of pressure, creating a powerful shock wave. Left: real-time pressure. Right: maximum pressure, where each pixel displays the highest pressure it has experienced.

Our simulations support that the ground effects from an asteroid blown apart by PI are vastly less damaging than if the asteroid hit Earth intact. For example, we find that a 50-meter-diameter asteroid that is broken into 1000 fragments only one day before Earth impact is vastly less damaging than if it was left intact (Figure 3 versus Figure 4). In the mitigated scenario, we estimate that the observation area (±150 km from the fragment cloud’s center) would experience an average pressure of ~0.4 kPa and a maximum pressure of ~2 kPa (Figure 3). In the unfragmented asteroid case (as in, not broken up), we estimate an average pressure of ~3 kPa and a maximum pressure of ~20 kPa (Figure 4). The asteroid mitigated by PI keeps all areas below the 3 kPa damage threshold, while the maximum pressure in the unmitigated case is almost seven times higher than the threshold.

The key is that the shock waves from the many fragments are “de-correlated” at any given observer, and hence vastly less threatening. Our findings suggest that PI is an effective approach for planetary defense that can be used in both short-warning (“terminal” scenarios) and extended warning scenarios, to result in little to no ground damage.

While we would rather not use this terminal defense mode–as it is preferable to intercept asteroids far ahead of time–PI’s short-warning mode could be used to mitigate threats that we fail to see coming. We envision that asteroid impact events similar to the in Chelyabinsk airburst in 2013 (~20 m diameter) or Tunguska airburst in 1908 (~40-50 m diameter) could be effectively mitigated by PI with remarkably short intercepts and relatively little intercept mass.

Website and additional resources
Please see our website for further information regarding the PI project, including papers, visuals, and simulations. For our full suite of ground effects simulations, please check our YouTube channel.

Funding
Funding for this program comes from NASA NIAC Phase I grant 80NSSC22K0764 , NASA NIAC Phase II grant 80NSSC23K0966, NASA California Space Grant NNX10AT93H and the Emmett and Gladys W. fund. We gratefully acknowledge support from the NASA Ames High End Computing Capability (HECC) and Lawrence Livermore National Laboratory (LLNL) for the use of their ALE3D simulation tools used for modeling the hypervelocity penetrator impacts, as well as funding from NVIDIA for an Academic Hardware Grant for a high-end GPU to speed up ground effect simulations.

Listening for bubbles to make scuba diving safer

Joshua Currens – jcurrens@unc.edu

Department of Radiology; Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States

Popular version of 5aBAb8 – Towards real-time decompression sickness mitigation using wearable capacitive micromachined ultrasonic transducer arrays
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0027683

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Scuba diving is a fun recreational activity but carries the risk of decompression sickness (DCS), commonly known as ‘the bends’. This condition occurs when divers ascend too quickly, causing gas that has accumulated in their bodies to expand rapidly into larger bubbles—similar to the fizz when a soda can is opened.

To prevent this, divers will follow specific safety protocols that limit how fast they rise to the surface and stop at predetermined depths to allow bubbles in their body to dissipate. However, these are general guidelines that do not account for every person in every situation. This limitation can make it harder to prevent DCS effectively in all individuals without unnecessarily lengthening the time to ascend for a large portion of divers. Traditionally, these bubbles have only been detected with ultrasound technology after the diver has surfaced, so it is a challenge to predict DCS before it occurs (Figure 1b&c). Early identification of these bubbles could allow for the development of personalized underwater instructions to bring divers back to the surface and minimize the risk of DCS.

To address this challenge, our team is creating a wearable ultrasound device that divers can use underwater.

Ultrasound works by sending sound waves into the body and then receiving the echoes that bounce back. Bubbles reflect these sound waves strongly, making them visible in ultrasound images (Figure 1d). Unlike traditional ultrasound systems that are too large and not suited for underwater use, our innovative device will be compact and efficient, designed specifically for real-time bubble monitoring while diving.

Currently, our research involves testing this technology and optimizing imaging parameters in controlled environments like hyperbaric chambers. These are specialized rooms where underwater conditions can be replicated by increasing the inside pressure. We recently collected the first ultrasound scans of human divers during a hyperbaric chamber dive with a research ultrasound system, and next we plan to use it with our first prototype. With this data, we hope to find changes in the images that indicate where bubbles are forming. In the future, we plan to start testing our custom ultrasound tool on divers, which will be a big step towards continuously monitoring divers underwater, and eventually personalized DCS prevention.

Figure 1. (a) Scuba diver underwater. (b) Post-dive monitoring for bubbles using ultrasound. (c) Typical ultrasound system (developed using Biorender). (d) Bubbles detected in ultrasound images as bright spots in heart. Images courtesy of JC, unless otherwise noted.

Unlocking the Secrets of Ocean Dynamics: Insights from ALMA

Florent Le Courtois – florent.lecourtois@gmail.com

DGA Tn, Toulon, Var, 83000, France

Samuel Pinson, École Navale, Rue du Poulmic, 29160 Lanvéoc, France
Victor Quilfen, Shom, 13 Rue de Châtellier, 29200 Brest, France
Gaultier Real, CMRE, Viale S. Bartolomeo, 400, 19126 La Spezia, Italy
Dominique Fattaccioli, DGA Tn, Avenue de la Tour Royale, 83000 Toulon, France

Popular version of 4aUW7 – The Acoustic Laboratory for Marine Applications (ALMA) applied to fluctuating environment analysis
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0027503

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Ocean dynamics happen at various spatial and temporal scales. They cause the displacement and the mixing of water bodies of different temperatures. Acoustic propagation is strongly impacted by these fluctuations as sound speed depends mainly on the underwater temperature. Monitoring underwater acoustic propagation and its fluctuations remains a scientific challenge, especially at mid-frequency (typically the order of 1 to 10 kHz). Dedicated measurement campaigns have to be conducted to increase the understanding of the fluctuations, their impacts on the acoustic propagation and thus to develop appropriate localization processing.

The Acoustic Laboratory for Marine Application (ALMA) has been proposed by the French MOD Procurement Agency (DGA) to conduct research for passive and active sonar since 2014, in support of future sonar array design and processing. Since its inception in 2014, ALMA has undergone remarkable transformations, evolving from a modest array of hydrophones to a sophisticated system equipped with 192 hydrophones and advanced technology. With each upgrade, ALMA’s capabilities have expanded, allowing us to delve deeper into the secrets of the sea.

Figure 1. Evolution of the ALMA array configuration, from 2014 to 2020. Real and Fattacioli, 2018

Bulletin of sea temperature to understand the acoustic propagation
The campaign of 2016 took place Nov 7 – 17, 2016, off the Western Coast of Corsica in the Mediterranean Sea, located by the blue dot in Fig.2 (around 42.4 °N and 9.5 °E). We analyzed signals from a controlled acoustic source and temperature recording, corresponding approximately to 14 hours of data.

Figure 2. Map of surface temperature during the campaign. Heavy rains of previous days caused a vortex in the north of Corsica. Pinson et. al, 2022

The map of sea temperature during the campaign was computed. It is similar to a weather bulletin for the sea. From previous days, heavy rains caused a global cooling over the areas. A vortex appeared in the Ligurian Sea between Italy and the North of Corsica. Then the cold waters traveled Southward along Corsica Western coast to reach the measurement area. The water cooling was measured as well on the thermometers. The main objective was to understand the changes in the echo pattern in relation to the temperature change. Echos can characterize the acoustic paths. We are mainly interested in the amplitude, the time of travel and the angle of arrival of echoes to describe the acoustic path between the source and ALMA array.

All echoes extracted by processing ALMA data are plotted as dots in 3D. They depend on the time of the campaign, the angle of arrival and the time of flight. The loudness of the echo is indicated by the colorscale. The 3D image is sliced in Fig. 3 a), b) and c) for better readability. The directions of the last reflection are estimated in Fig. 3 a): positive angles come from the surface reflection while negative angles come from seabed reflection. The global cooling of the waters caused a slowly increasing fluctuation of the time of flight between the source and the array in Fig. 3 b). A surprising result was a group of spooky arrivals, who appeared briefly during the campaign at an angle close to 0 ° during 3 and 12 AM in Fig. 3 b) and c).

All the echoes detected by processing the acoustic data. Pinson et. al, 2022

Figure 3. Evolution of the acoustic paths during the campaign. Each path is a dot defined by the time of flight and the angle of arrival during the period of the campaign. Pinson et. al, 2022

The acoustic paths were computed using the bulletin of sea temperature. A more focused map of the depth of separation between cold and warm waters, also called mixing layer depths (MLD), is plotted in Fig 4. We noticed that, when the mixing layer depth is below the depth of the source, the cooling causes acoustic paths to be trapped by bathymetry in the lower part of the water column. It explains the apparition of the spooky echoes. Trapped paths are plotted in the blue line while regular paths are plotted in black in Fig. 5.

Figure 4. Evolution of the depth of separation between cold and warm water during the campaign. Pinson et. al, 2022

Figure 5. Example of acoustic paths in the area: black lines indicate regular propagation of the sound; blue lines indicate the trapped paths of the spooky echoes. Pinson et. al, 2022

Overview
The ALMA system and the associated tools allowed illustrating practical ocean acoustics phenomena. ALMA has been deployed during 5 campaigns, representing 50 days at sea, mostly in the Western Mediterranean Sea, but also in the Atlantic to tackle other complex physical problems.

Taking Pictures of the Sound of a Rocket

Grant W. Hart – grant_hart@byu.edu
Brigham Young University
Provo, UT 84602
United States

Kent Gee (@KentLGee on X)
Eric Hintz
Giovanna Nuccitelli
Trevor Mahlmann (@TrevorMahlmann on X)

Popular version of 1pNSa8 – A photographic analysis of Mach wave radiation from a rocket plume
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0026810

The rumble of a large rocket launching is one of the loudest non-explosive sounds that mankind has ever made. Where does that sound come from? Surprisingly, it doesn’t come from the rocket itself, or even the exhaust nozzle, but rather from the plume of exhaust that shoots out of the back. The plume is supersonic when it comes out of the rocket, and it emits sound as it slows down in the atmosphere.

This process was visualized in some recent pictures taken by Trevor Mahlmann of a Falcon 9 launch from Cape Canaveral. The launch was just after dawn, and Mahlmann took a series of striking pictures as the rocket passed in front of the sun. Two of those pictures are shown below. If you look at the edge of the sun in the later picture you can see distortions caused by the intense sound waves coming from the rocket.

Recognizing the possibility of gaining more information from these pictures, researchers at Brigham Young University got permission from Mr. Mahlmann to further analyze them. The third picture below shows a portion of the difference between the first two pictures. The colors have been modified to show the sound waves more clearly. The waves clearly are coming from a region far down the plume of the rocket, rather than the nozzle of the rocket. The source was typically about 10-25 times the diameter of the rocket down the plume.

The sound is also directional – it doesn’t go out evenly in all directions, but rather goes out most strongly at about 20-30 degrees below the horizontal. Most rockets sound loudest to people watching the launch when they are 20-30 degrees above the ground. This is all consistent with the models of the sound being produced by the processes that slow down the exhaust from supersonic speeds. A good introduction to rocket noise is found in a recent article in Physics Today.

The researchers first had to line up the images so that the sun was in the same place in each frame. They were then able to subtract the later image from the first one to get the difference and leave just the distortions caused by the waves in the second image. To find the source of the waves, it was necessary to draw a line backward from the wave’s image and find where it met the rocket’s path across the Sun. Since it took time for the wave to get from the source to where it was observed, they had to find where the rocket was at the time the sound wave was given off. They did this by finding how far the sound had traveled and used the speed of sound to find the time it took to get there. With that information the researchers could find the position of the source and the direction of the wave.

Figure 1. A Falcon 9 rocket about to pass in front of the Sun. Image courtesy of Trevor Mahlmann. Used by permission. Higher resolution versions available from the photographer.

Figure 2. A Falcon 9 rocket passing in front of the Sun. Note the distortions of the edge of the Sun caused by the sound waves produced by the rocket. Image courtesy of Trevor Mahlmann. Used by permission. Higher resolution versions available from the photographer.

Figure 3. A portion of the difference between the two previous figures, showing the enhanced sound waves. The bottom of the rocket is at the top of the image. Image adapted from Hart et al.’s original paper.