3pSP4 – Imaging Watermelons

Dr. David Joseph Zartman
Zartman Inc., L.L.C.,
zartman.david@gmail.com
Loveland, Colorado

Popular version of 3pSP4 – Imaging watermelons
Presented Wednesday afternoon, May 25, 2022
182nd ASA Meeting, Denver
Click here to read the abstract

When imaging watermelons, everything can be simplified down to measuring a variable called ripeness, which is a measure of the internal medium of the watermelon, rather than looking for internal reflections from any contents such as seeds. The optimal experimental approach acoustically is thus a through measurement, exciting the wave on one side and measuring the result on the other.

Before investigating the acoustic properties, it is useful to examine watermelons’ ripening properties from a material perspective.  As the fruit develops, it starts off very hard and fibrous with a thick skin. Striking an object like this would be similar to hitting a rock, or possibly a stick given the fibrous nature of the internal contents of the watermelon.

As the watermelon ripens, this solid fiber starts to contain more and more liquid, which also sweetens over time. This process continues and transforms the fruit from something too fibrous and bitter to something juicy and sweet. Most people have their own preference for exactly how crunchy versus sweet they personally prefer. The skin also thins throughout this process. As the fibers continue to be broken down beyond optimal ripeness, the fruit becomes mostly fluid, possibly overly sweet, and with a very thin skin.  Striking the fruit at this stage would be similar to hitting some sort of water balloon. While the sweet juice sounds like a positive, the overall texture at the stage is usually not considered desirable.

In review, as watermelons ripen, they transform from something extremely solid to something more resembling a liquid filled water balloon. These are the under-ripe and over-ripe conditions; thus, the personal ideal exists somewhere between the two. Some choose to focus on the crunchy earlier stage at the cost of some of the sweetness, possibly also preferable to anyone struggling with blood sugar issues, in contrast to those preferring to maximize the sweet juicy nature of the later stages at the cost of crunchy texture.

The common form of acoustic measurement in this situation is to simply strike the surface of the watermelon with a finger knuckle and listen to the sound. More accuracy is possible by feeling with fingertips on the opposite side of the watermelon when it is struck. Both young and old fruit do not have much response, one being too hard, getting an immediate sharp response and being more painful on the impacting finger. The other is more liquid and thus is more difficult to sonically excite. A young watermelon may make a sound described as a hard ‘tink’, while an old one could be described more as a soft ‘phlub’. In between, it is possible to feel the fibers in the liquid vibrating for a period of time, creating a sound more like a ‘toong’. A shorter resonance, ‘tong’, indicates younger fruit, while more difficulty getting a sound through, ‘tung’, indicates older.

An optimal watermelon can thus be chosen by feeling or hearing the resonant properties of the fruit when it is struck and choosing to preference.

2aPAa – Three-dimensional wavefront modeling of secondary sonic booms

Dr. Joe Salamone – joe.salamone@boom.aero
Boom Supersonic
12876 East Adam Circle
Centennial, CO 80112

Popular version of 2aPAan- Three-dimensional wavefront modeling of secondary sonic booms
Presented Tuesday morning, May 24, 2022
182nd ASA Meeting, Denver, Colorado
Click here to read the abstract

A sonic boom is the impulsive sound heard resulting from a vehicle flying faster than the speed of sound.  The origin of this impulsive sound is the localized shock structure close to the vehicle due to regions of compression and expansion of the air (Figure 1) which manifest as pressure disturbances.  The leading shock at the vehicle typically forms a cone that circumferentially spreads around its nose.  A commonly used formula that relates the interior cone angle to the supersonic vehicle’s Mach number is:  cone angle = asin(1/Mach).  Thus, the cone angle gets larger with decreasing supersonic Mach number and vice versa.

The sonic boom propagates along acoustic ray paths, and these paths can refract based on temperature gradients and wind speed gradients.  A fundamental premise is the ray path will always bend towards the slower speed of sound.  The initial ray direction is normal to the Mach cone, with some additional influence for its initial direction due to the presence of wind at the vehicle’s flight altitude.  A depiction of the Mach cone compared to the ray cone was presented by Plotkin (2008) shown in Figure 2.  The Mach cone exists at an instance in time, travelling with the supersonic vehicle, while the specific locations that comprise the Mach cone surface represent the pressure disturbances that propagate along ray paths.

sonic booms

Figure 2 – Notional comparison between the supersonic Mach cone and its corresponding ray cone

Work presented here examines the shape of the Mach cone when propagated significantly large distances away from the vehicle in three-dimensional, realistic atmospheric conditions.  Also recognize the work here only depicts where the sonic boom could travel and not what its amplitude could be at the Earth’s surface.  Figure 3 shows that as the vehicle travels it is constantly generating new portions of the Mach cone, while the existing portions of the Mach cone all propagate at the local (effective) speed of sound.

Figure 3 – Mach cone construction from ray paths that originate from vehicle positions along its trajectory

A computational example of an extended Mach cone is shown in Figure 4 where the vehicle is flying at Mach 1.15.  Note the atmospheric refraction of the ray paths result in the lower portions of the Mach cone not reaching the Earth’s surface.  And likewise, the upper portions of Mach cone warp back towards the Earth’s surface.  Thus, the Mach cone no longer resembles a cone but is a more complicated shape.

Figure 4 – Computational example of a Mach cone for a vehicle traveling at Mach 1.15

Another computational example is presented in Figure 5, where the vehicle is flying at Mach 1.7.  Note the increase in Mach number creates a shallower initial Mach cone and portions of the Mach cone reach the Earth’s surface.  Additionally, the outer fringes of the Mach cone above and below the vehicle that do reach the Earth’s surface result in primary, direct secondary and indirect secondary sonic booms as indicated in Figure 5.  However, some portions of the Mach cone centered above and below the vehicle eventually refract at an extremely high altitude in the thermosphere.  Thus, those portions of the Mach cone, when they reach the Earth’s surface, would be inaudible due to their significantly longer propagation distances.

Figure 5 – Computational example of a Mach cone for a vehicle traveling at Mach 1.7

3aPPb1 – Spectral Processing Deficits Appear to Underlie Developmental Language Disorders

Susan Nittrouer, snittrouer@phhp.ufl.edu
Joanna H. Lowenstein
Kayla Tellez
Priscilla O’Hara
Donal G. Sinex

Popular version of 3aPPb1 Spectral processing deficits appear to underlie developmental language disorders
Presented Wednesday morning, May 25, 2022
182nd ASA Meeting
Click here to read the abstract

The Problem
Sophisticated oral and written language skills are essential to academic and occupational success in our modern, technically based society. Unfortunately, as many as twenty percent of children encounter difficulties learning language, a condition termed Developmental Language Disorder (DLD). This work was undertaken to try to uncover the root of these problems.

Brief Background
For 50 years, scientists have hypothesized that auditory problems are at the root of the challenges encountered by children with DLD. The idea is that children with DLD simply cannot recognize the acoustic structure in speech signals that underlies linguistic forms. Work in this area, however, has been fraught with controversy, and at present, no agreed-upon explanation exists.

What we did
We believe that children with DLD likely have problems processing the acoustic speech signal. In our work we changed three components of our approach from earlier work.

  1. Auditory problems are likely worst at young ages and disrupt language learning at the initial stages. The auditory problems may eventually resolve, but children may be left with language deficits. We looked across ages 7-10 years for evidence of auditory problems that might be more severe in younger than older
  2. The critical auditory problems may involve spectral (frequency), rather than temporal structure, as commonly manipulated. The spectral structure of speech signals is most responsible for defining linguistic We tested children on their ability to detect both temporal and spectral structure. Watch video here.
  3. Word-internal elements, known as phonological units (or simply phonemes), may be disproportionately affected by auditory problems, rather than vocabulary or syntactic We tested all three kinds of skills: vocabulary, syntax, and phonology, with a focus on phonological skills. We expected to find the strongest effects of auditory problems on those phonological skills.

What we found

  1. Younger children with DLD showed more severe auditory problems than older children with
  2. Problems detecting spectral structure were more severe for children with DLD and lasted longer across age than problems detecting temporal
  3. Problems with spectral structure were most strongly related to children’s awareness of phonological units, rather than lexical or syntactic

Developmental Language Disorder

Significance
These findings should serve to refocus research efforts on different kinds of acoustic structure than those examined previously, as well as on specific language deficits. DLD puts children at serious risk for problems in school that can masquerade as other disorders, such as attention deficit or reading problems. Underlying conditions – including premature birth and frequent ear infections in infancy – can cause the kinds of auditory problems identified in the work reported here, and unfortunately, children living in poverty face healthcare inequities that put them at risk for those medical problems. This work is one more step in efforts to achieve equity in educational outcomes.

1pEA7 – Oscillations of drag-reducing air pocket under fast boat hull

Konstantin Matveev – matveev@wsu.edu

Washington State University
Pullman, WA 99164

Popular version of 1pEA7 – Acoustic oscillations of drag-reducing air pocket under fast boat with stepped bottom
Presented Monday afternoon, May 23, 2022
182nd ASA Meeting
Click here to read the abstract

A lot of fuel is usually consumed by a fast boat to overcome water drag. Some of this resistance is caused by water friction which scales with the hull wetted area. By injecting air under the hull bottom with a special recess and maintaining a thin but large-area air pocket, total boat drag can be decreased by up to 30%.

boat hull

Boat with bottom air cavity.

However, generating and keeping the bottom air pocket in waves is rather tricky, as periodic wave pressure may excite an acoustic resonance in a compliant air cavity, resulting in large oscillations of the air cavity accompanied by significant loss of air to the surrounding water flow. The deterioration of the air pocket will drastically increase resistance of the hull, and the boat may be unable to reach sufficiently high speeds to operate in a planing regime.

Side view of air-cavity hull in waves.

Bottom view of air-cavity hull in waves, showing increased air leakage.

A simplified oscillator model, similar to a mass on a spring, is employed in this study to describe and simulate oscillations of the air cavity under the boat hull. The main inertia in this process is the so-called added water mass, which is a mass of an effective water volume under the air pocket, while the spring action comes from the compressibility of air inside the bottom recess.

boat hull

Oscillator model for air cavity under hull in waves.

An air-cavity boat accelerating through waves may hit the resonance condition, when a frequency of encounter with waves coincides with the natural or preferable oscillation frequency of the air pocket under the hull. Simulations using the developed model have demonstrated that acoustic oscillations may grow in magnitude and disintegrate the air cavity. However, if the boat accelerates sufficiently fast and the time spent near the resonance state is short, then oscillations will not have enough time to amplify, and the boat can successfully reach a high speed to glide on the water surface. Alternatively, if the damping is increased, for example by baffles, morphing surfaces or even sound from underwater loudspeakers, one can suppress the oscillation growth as well. The presented model can help boat designers develop higher performance boats.

4pBA8 – Charging devices inside the body or outside: Ultrasound Wireless Powering offers several possibilities

Inder Makin, inder.makin@gmail.com
Piezo Energy Technologies, LLC
Mesa, AZ

Popular version of 4pBA8 – Charging of devices for healthcare applications, using ultrasound wireless power
Presented Thursday afternoon, May 26, 2022
182nd ASA Meeting
Click here to read the abstract

The current technology in our daily lives including medical devices, requires electrical power. Preferably, these devices use batteries, making the systems portable and easy to use. Alas we all have experienced a power-deprived cell phone or tablet, which we wished would be easily chargeable without a cable. Similarly, devices such as pacemakers and neurostimulators, implanted inside the patient’s body need charging. Each of these scenarios – from real-world power needs to powering implants, would best require a wireless solution to keep the batteries charged, and devices functioning.

The “high-school taught” piezo-electric effect, is practically leveraged by Arizona scientists, Drs. Inder Makin and Leon Radziemski, to provide wireless ultrasound powering (UWP) for several applications. A mm-thin (1/32”), ultrasound disk vibrates at a fixed pitch (frequency), when a voltage is applied across its face. The vibrations propagate through material, such as body tissue (not very efficient in air!). Conversely, a similar disk placed in a material medium where a vibrational beam is present, will generate a voltage at the frequency of the vibration, converting ultrasound to electrical power. The use of an ultrasound transmitter and receiver approach has enabled wireless ultrasound powering (UWP), from sophisticated body-implant powering to charging batteries for digital devices, like smartphones and tablets used primarily in healthcare settings – clinics, emergency rooms, procedure suites.

The video below demonstrates the charging of an implant battery – UltraSound electrical Recharging (USer), using a simple, light device the size of a hockey puck that is attached to the skin. The transmitter senses the need for power in the implant, charges the battery, and communicates to the end user, that it is done.

 

This concept was tested in live animal studies, in order to prove feasibility and safety of the procedure. When a miniaturized implant prototype with a piezo-receiver, was placed inside a pig’s body. The ultrasound transmitter safely charged the implant battery in less than 30 minutes.

Since ultrasound energy can be steered electronically, while the device is compact, the USer concept can be made fully hands free as shown in the figure below. Sensors on the Transmitter and Receiver sense the misalignment and the beam corrects itself to efficiently charge the battery.

ultrasound

Broadening its applications, Piezo Energy Technologies, has demonstrated the charging of smart phones and other digital devices, without wires, using their patented technology. The picture below shows prototypes which are used for efficient charging of a smartphone.Ultrasound Wireless Powering

Multiple devices can be charged simultaneously, such as on top of a Ultrasound-PowerTM Pod. In these days of infection control requirements, using a wireless charging system is highly desired, anyway.

Why ultrasound? Compared to existing electromagnetic wireless devices, ultrasound can propagate efficiently through several solid and liquid materials, including metals. The transmitted ultrasound beam is like a flashlight, causing no stray energy, especially due to very inefficient ultrasound propagation through air.

The electronically steerable energy travels to the receiver where it is needed, and reduces one less source of wireless electromagnetic radiation in our daily environment!