1aBAb1 – Acoustic intra-body communication using semi-guided waves through human body tissues

John O. Gerguis – jgerguis@purdue.edu
Mayukh Nath – nathm@purdue.edu
Shreyas Sen – shreyas@purdue.edu
Purdue University
516 Northwestern Ave
West Lafayette, IN, USA 47906

Popular version of 1aBAb1 – Ultrasonic intra-body communication using semi-guided waves through human body tissues
Presented Monday morning, November 29, 2021
181st  ASA Meeting in Seattle, Washington
Read the article in Proceedings of Meetings on Acoustics

The considerable attention that the Internet of Things (IOT) received in the recent years, has led to the development of low-cost and miniaturized devices. One of the fields that had a chance to benefit from this development is the Body Area Network (BAN), which is a network across the human body used to connect wearable and implantable devices.

Traditionally, Radio Frequency signals are used for the communication between devices across the BAN, which suffer from high losses and lack of security. Recently, electro-quasistatic human body communication, that uses the body as a wire, has emerged as an alternative – enabling low-power communication, and ultra-low leakage from human body (Das et al., 2019).

Acoustic waves have a better ability than Radio Frequency waves to propagate through water-dominant media, like the human body, besides being safe and physically secured in the body. Hence, ultrasounds present a promising alternative for the communication between wearable and/or implantable devices across the BAN.

In this work, a theoretical study was presented to explore the possibility of using ultrasounds for the communication between devices attached on the body. The ultrasound waves are confined inside the human tissues (muscle, fat and skin), thus a secure communication can be achieved, making it difficult for eavesdroppers to snoop the transmitted signal. (see Figure 1).

communication

Figure 1 “Intrabody communication between wearable devices through ultrasonic waves”

The confinement is achieved by avoiding the bone, a highly-attenuative tissue (has an attenuation of almost an order of magnitude higher than the other main tissues of the body), by having a total internal reflection on the bone/muscle interface through oblique incidence of ultrasounds on that interface. From the other side, the high acoustic impedance mismatch between the air and the skin, the outer layer of the human body, allows high reflection of the signal at the skin/air interface (~99.9%), thus confining most of the signal inside the body. By using directional acoustic wave propagation through the body and using total internal reflection, besides avoiding the bone, non-line-of-sight communication can be achieved as well between wearable devices with longer separations. This communication mechanism might be suitable in regions with thick bone (e.g. the leg).

Simulations are performed at an acoustic frequency of 100 kHz on a simplified cylindrical-shaped human body model, consisting of concentric layers of the four main tissues that form the human body: bone, muscle, fat and skin.

Figure 2. Total internal reflection of the acoustic waves on the bone.

Total internal reflection on the bone is shown in Figure 2 , where a transmitter is placed in location A and the receiver should be placed in location B. Figure 3(a) shows a ray tracing for the transmitted acoustic wave from the transmitter to the receiver, while Figure 3(b) shows the power density distribution at the receiver site. A communication between wearable devices across a distance of around 1m is shown to be possible with losses < 50 dB and with leakage signal which is >20 dB below the received signal, hence making the communication secure.

Figure 3(a). Ray tracing for the transmitted acoustic waves from the transmitter to the receiver.

 Figure 3(b). Power density distribution at the receiver site.

2pCA8 – Sonic boom propagation using an improved ray tracing technique

Kimberly Riegel – kriegel@qcc.cuny.edu
William Costa
George Seaton
Christian Gomez
Queensborough Community College
222-05 56th Avenue
Bayside, NY 11364

Popular version of 2pCA8 – Sonic boom propagation in a non-homogeneous atmosphere using a stratified ray tracing technique’
Presented Tuesday afternoon, November 30, 2019
181st ASA Meeting
Click here to read the abstract

Supersonic air travel could reduce flight times by half, vastly improving long range air travel. To make this type of travel commercially viable, however, the current ban on overland flight would need to be lifted while ensuring residents below are still protected from the high noise levels in the flight paths of these new aircraft. There has been a recent increase in supersonic aircraft investment. United Airlines just invested in 15 supersonic jets provided by BOOM supersonic. These aircraft are expected to fly in 2029 but will remain restricted to over water flight. Lockheed Martin in partnership with NASA is building a low boom demonstrator aircraft. This aircraft is expected to perform some community-based test flights next year. Therefore, a computationally efficient prediction tool that can predict the impact of sonic booms in urban areas would be a useful tool for researchers and legislators.

Previously a ray tracing simulation tool to predict the sound behavior in urban environments was developed. The simulation included the ability to read in 3D renderings of the environments. This made it possible to simulate any complicated shape including detailed buildings and multiple buildings. All surfaces are represented by a mesh of triangular faces. The more complicated the building, the more triangles were required to accurately represent it. The biggest limitation of the code was that it could take several days to complete one simulation of a complicated building. The purpose of this work is to reduce the computational time to make the numerical simulation more accessible while not sacrificing the accuracy of the results.

In order to reduce the computation time for complex geometries the entire environment was cut into horizontal slices. Only the slice where the origin of the ray is considered at a time. This allows for a significant reduction in the number of building facets that needs to be assessed for each step. Figure 1 shows the total building in grey and the slice under consideration in green.

 

[IMAGE MISSING]
Figure 1. Representation of a simple building/ray interaction and the vertical slices where the building is segmented.

To determine how the modifications to the code improved the result, several environments were run and compared to those environments for previous version of the code. Table 1 shows the improvements. From the timing of the different versions of the code it is clear that updates to the code have drastically reduced the computation times for complex environments. The resulting pressures at the receivers have no noticeable difference in the pressure results. This will improve the useability of the simulation and make it more convenient to predict sonic booms in urban areas.

1aBAb – Detecting liver cracks using ultrasonic shear wave imaging

Jingfei Liu – jingfei.liu@ttu.edu
Texas Tech University
2500 Broadway
Lubbock, TX 79409

Popular version of 1aBAb – An ex vivo investigation of ultrasonic shear wave imaging for detecting liver cracks
Presented Monday morning, November 29, 2021
181st ASA Meeting
Click here to read the abstract

Liver crack is a type of liver trauma, in which a capsular tear of different geometries occurs due to external impacts, and it is a common physical damage in traffic accidents, combating sports, and other accidents. Since liver crack is an important source of morbidity and mortality in emergency medicine, a timely and accurate detection of the crack location and geometry is highly demanded. In current emergency care, ultrasonography, although has a low accuracy, is mostly used for initial examination of liver trauma due to its immediate availability, high mobility, and nonionizing nature. After the initial screening using ultrasonography, a more accurate diagnosis is normally achieved by X-ray computer tomography (CT). Although CT can provide more details of the liver damage, it is not easy to access because patients must be transport to CT facilities, and it is even risky for the patients like newborns whose condition is unstable. To develop a diagnostic technique which both has easy access and can provide accurate diagnosis, ultrasonic shear wave imaging was proposed in this study as a better option.

In this technique, shear wave, a different type of ultrasonic wave from the ultrasonic wave (longitudinal wave) used in typical ultrasonography, is first generated at the patients’ liver, and then tracked during its propagation. Because shear wave cannot propagate in blood, there will be strong reflection or diffraction at the crack locations, which ultrasonography cannot identify (because longitudinal wave can go through blood and no strong reflection is available). Thus, the location and severeness of targeted liver crack can possibly be detected.

In this study, the feasibility and effectiveness of this method was investigated in an ex vivo scenario. A porcine liver with cracks of different geometries was tested. Shear waves were generated using acoustic radiation force impulse and recorded using ultrafast ultrasound imaging. To find the best way to display the cracks, different methods of signal processing based on time-of-flight, shear wave modulus, and accumulated shear wave path were applied to the shear wave displacement extracted. The results show that shear wave imaging is a more sensitive method than the conventional ultrasonography in detecting liver cracks.

4aAA9 – The successful application of acoustic lighting in restaurants

Zackery Belanger, zb@arcgeometer.com
Arcgeometer LC, Detroit, MI

Popular version of 4aAA9 – The successful application of acoustic lighting in restaurants’
Presented Thursday morning, December 2, 2021
181st ASA Meeting, Seattle, WA
Click here to read the abstract

To understand the rise of acoustic lighting in restaurants, it is best to go back to the beginning of modern architectural acoustics. In 1895, Harvard University opened the new Fogg Art Museum with its centerpiece lecture hall, which failed immediately due to the room’s tendency to sustain sound. The reverberation was so long the voice of the lecturer would drown itself. Given that neither an acoustic product industry nor the acousticians who prescribed them yet existed, Harvard could do only one thing: appeal to their own physics department. A sympathetic ear was found in graduate student Wallace Clement Sabine who, through tedious work and borrowed seat cushions from a nearby theater, came to understand the sound of the hall and how to fix it. Seat cushions started all this, and the remarkable thing is that they were likely never intended to be acoustic at all.

As 20th century design marched on, the ornament went away, the surfaces flattened, and reverberation flourished. The acoustic product industry arose with dedicated, engineered acoustic surfaces to counter this change, and architecture largely forgot that everything else about architecture still had acoustic properties.

Lighting, like seat cushions, was always acoustic because it has form and a physical presence. It was only a matter of time before lighting designers began to ask how they could have more acoustic influence. This happened recently with informed shifts in the material and scale of their designs, and lighting stepped firmly into the realm of reverberation control.

Arcgeometer-Light-Fixture-Simulation

[Arcgeometer-Light-Fixture-Simulation.mp4, Simulation of the acoustic influence of traditional lighting]

The common problem in restaurant acoustics is excessive noise, which results when patrons feel they are not being heard. They subconsciously raise their voices to compensate for poor acoustics. The solution can be quite simple: get enough absorption in the room to change the behavior of the crowds. Give them acoustic comfort. Since restaurant owners and patrons tend to enjoy a sense of liveliness, the amount of absorption needed to fix a room is usually fairly low.

[LightArt-Echo-300-S-Wacker.jpg, A Chicago cafe with a prevalence of planar glass]
Credit: Courtesy of LightArt
300 S Wacker St.
Photo by Huntsman Architectural Group

Other barriers to good acoustics arise, including visual design, conflict with elements like sprinklers, post-opening timing, and a lack of confidence in proposed solutions. Restaurant owners with noisy crowds consider it a good problem to have, and are averse to big changes no matter how poor the acoustics of the space. This is where tapping into lighting makes sense. Lighting is usually meant to be seen, is accepted as something more centrally-located in spaces, can be integrated with other acoustically absorptive surfaces, is easy to install, and has the indispensable primary function of providing light.

[LightArt-Penn-State.jpg, Acoustic lighting integrated with other absorption]]
Credit: Courtesy of LightArt
Penn State Health, Hampden Medical Center
Photo by CannonDesign

The efficacy of this approach has been demonstrated with lab results that confirm the performance of these fixtures, and with numerous case studies in existing and new restaurants. Acoustic lighting brings reverberation control in a way that is palatable to restaurant owners, and in doing so may lead the way into a future for acoustics that re-integrates the forgotten influence of everything else. It is hard to imagine furniture, art, textiles, plants, and all manner of visual presences not following suit.

[LightArt-Echo-Portage-Bay.jpg, A restaurant that was acoustically improved with lighting.]
Credit: Courtesy of LightArt
Portage Bay Cafe
Photo by Chris Bowden

 

 

Filtering Microplastics Trash from Water with Acoustic Waves

Filtering Microplastics Trash from Water with Acoustic Waves

Prototype speaker system efficiently separates out microplastics from polluted water

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

SEATTLE, November 29, 2021 — Microplastics are released into the environment by cosmetics, clothing, and industrial processes or from larger plastic products as they break down naturally.

The pollutants eventually find their way into rivers and oceans, posing problems for marine life. Filtering and removing the small particles from water is a difficult task, but acoustic waves may provide a solution.

Dhany Arifianto, of the Institut Teknologi Sepuluh Nopember in Surabaya, Indonesia, will discuss a filtration prototype in his presentation, “Using bulk acoustic waves for filtering microplastic on polluted water,” on Monday, Nov. 29 at 6:10 p.m. Eastern U.S. at the Hyatt Regency Seattle. The presentation is part of the 181st Meeting of the Acoustical Society of America, taking place Nov. 29 to Dec. 3.

Arifianto and his team used two speakers to create acoustic waves. The force produced by the waves separates the microplastics from the water by creating pressure on a tube of inflowing water. As the tube splits into three channels, the microplastic particles are pressed toward the center as the clean water flows toward the two outer channels.

The prototype device cleaned 150 liters per hour of polluted water and was tested with three different microplastics. Each plastic was filtered with a different efficiency, but all were above 56% efficient in pure water and 58% efficient in seawater. Acoustic frequency, speaker-to-pipe distance, and density of the water all affected the amount of force generated and therefore the efficiency.

The acoustic waves may impact marine life if the wave frequency is in the audible range. The group is currently studying this potential issue.

“We believe further development is necessary to improve the cleaning rate, the efficiency, and particularly the safety of marine life,” said Arifianto.

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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/.