3D-Printed Violins Bring Music into More Hands #ASA183

3D-Printed Violins Bring Music into More Hands #ASA183

Modern materials and techniques can revolutionize music and provide access to low-cost instruments for music students.

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

NASHVILLE, Tenn., Dec. 6, 2022 – There’s nothing quite like the sound of a Stradivarius violin. Building such a quality string instrument takes time, perfect materials, and a lot of skill, and the best ones can cost millions of dollars. Even mediocre violins can cost thousands, which puts them out of reach for most beginners and music classrooms.

Dr. Mary-Elizabeth Brown rehearses Harry Stafylakis’ concerto “Singularity” on an early iteration of the 3D printed violin. Credit: Shawn Peters

One group is looking to rectify this by 3D-printing low-cost, durable violins for music students. In the process, they explored the factors that result in the best violin sounds and performed a concerto composed specifically for 3D-printed instruments.

Mary-Elizabeth Brown, Director of the AVIVA Young Artists Program, will discuss the steps taken and the lessons learned in her presentation, “Old meets new: 3D printing and the art of violin-making.” The presentation will take place on Dec. 6 at 10:35 a.m. Eastern U.S. in the Golden Eagle B room, as part of the 183rd Meeting of the Acoustical Society of America running Dec. 5- 9 at the Grand Hyatt Nashville Hotel.

“The team’s inspiration roots in multiple places,” said Brown. “Our goals were to explore the new sound world created by using new materials, to leverage the new technology being used in other disciplines, and to make music education sustainable and accessible through the printing of more durable instruments.”

The 3D-printed violin was created in two sections. The violin’s body is made of a plastic polymer material, in the same manner as a traditional acoustic violin, and designed to produce a resonant tone, while the neck and fingerboard are printed in smooth ABS plastic to be comfortable in the musician’s hands. The result is a violin that produces a darker, more mellow sound than traditionally made instruments.

“The next step is to explore design modifications as well as efforts to lower the costs of production while making such instruments more widely available, especially in the realm of education,” said Brown.

———————– MORE MEETING INFORMATION ———————–
Main meeting website: https://acousticalsociety.org/asa-meetings/
Technical program: https://eppro02.ativ.me/web/planner.php?id=ASAFALL22&proof=true

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
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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/.

Ultrasonics to monitor liquid metal melt pool dynamics for improving metal 3D printing

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.


MATLAB Handle Graphics – click here to watch the video.

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.

A moth’s ear inspires directional passive acoustic structures

Lara Díaz-García – lara.diaz-garcia@strath.ac.uk
Twitter: @laradigar23
Instagram: @laradigar

Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, Lanarkshire, G1 1RD, United Kingdom

Popular version of 2aSA1-Directional passive acoustic structures inspired by the ear of Achroia grisella, presented at the 183rd ASA Meeting.

When most people think of microphones, they think of the ones singers use or you would find in a karaoke machine, but they might not realize that much smaller microphones are all around us. Current smartphones have about three or four microphones that are small. The miniaturization of microphones is therefore a desire in technological development. These microphones are strategically placed to achieve directionality. Directionality means that the microphone’s goal is to discard undesirable noise coming from directions other than the speaker’s as well as to detect and transmit the sound signal. For hearing implant users this functionality is also desirable. Ideally, you want to be able to tell what direction a sound is coming from, as people with unimpaired hearing do.

But dealing with small size and directionality presents problems. People with unimpaired hearing can tell where sound is coming from by comparing the input received by each of our ears, conveniently sitting on opposite sides of our heads and therefore receiving sounds at slightly different times and with different intensities. The brain can do the math and compute what direction sound must be coming from. The problem is that, to use this trick, you need two microphones that are separated so the time of arrival and difference in intensity are not negligible, and that goes against microphone miniaturization. What to do if you want a small but directional microphone, then?

When looking for inspiration for novel solutions, scientists often look to nature, where energy efficiency and simple designs are prioritized in evolution. Insects are one such example that faces the challenge of directional hearing at small scales. The researchers have chosen to look at the lesser wax moth (fig 1), observed to have directional hearing in the 1980s. The males produce a mating call that the females can track even when one of their ears is pierced. This implies that, instead of using both ears as humans do, these moths’ directional hearing is achieved with just one ear.

Lesser wax moth specimen with scale bar. Image courtesy of Birgit E. Rhode (CC BY 4.0). Lesser wax moth specimen with scale bar. Image courtesy of Birgit E. Rhode (CC BY 4.0).

The working hypothesis is that directionality must be achieved by the asymmetrical shape and characteristics of the moth’s ear itself. To test this hypothesis, the researchers designed a model that resembles the moth’s ear and checked how it behaved when exposed to sound. The model consists of a thin elliptical membrane with two halves of different thicknesses. For it, they used a readily available commercial 3D printer that allows customization of the design and fabrication of samples in just a few hours. The samples were then placed on a turning surface and the behavior of the membrane in response to sound coming from different directions was investigated (fig 2). It was found that the membrane moves more when sound comes from one direction rather than all the others (fig 3), meaning the structure is therefore passively directional. This means it could inspire a single small directional microphone in the future.

Laboratory setup to turn the sample (in orange, center of the picture) and expose it to sound from the speaker (left of the picture). Researcher’s own picture.
Image adapted from Lara Díaz-García’s original paper. Sounds coming from 0º direction elicit a stronger movement in the membrane than other directions.

2pSA9 – Acoustic transients from the impact force excitation of beams and wind chimes

Peter Stepanishen, steppipr@uri.edu
University of Rhode Island
Department of Ocean Engineering
Narragansett, RI 02871

Popular version of paper 2pSA9
Presented on Tuesday December 3, 2019
178th ASA Meeting, San Diego, CA

The origin of wind chimes dates back to 1100 BC in Eastern and Southern Asia where the chimes were intended to ward off evil spirits and attract benevolent spirits. Modern wind chimes typically consist of 4 to 8 aluminum tubes with varying lengths and associated resonant frequencies corresponding to a specific musical scale. In addition the wind chimes also include a wind catcher and associated wind clapper to impact the chimes as illustrated in Figure 1 below:

The present paper addresses the underlying physics of wind chimes from the viewpoint of a structural acoustician.  The impact excitation and vibration of the structure is  addressed including the effects of the surrounding air on the vibration characteristics of the wind chime which is modeled as a sum of cylindrical pipes or beams. The directional characteristics of the transient acoustic field are then addressed.

The dominant sound producing features for each cylindrical pipe/beam are simply described as a sum of temporally decaying modal beam vibrations with different resonant frequencies which are inversely related to the square of the length of the pipe. A simple illustration of the predominant sound producing lowest frequency modal vibration is illustrated in the accompanying video:

wind chimes

The video simply illustrates the lowest modal vibration of a free free beam which is presented as a simple model of a cylindrical wind chime vis-à-vis a cylindrical shell model.  The ends of the beam/pipe undergo the maximum transverse deflection and vibration whereas two nodal points with zero deflection are also apparent for the fundamental modal vibration.  In contrast to stringed musical instruments, the higher order modal vibrations are associated with a nonharmonic series of resonant frequencies with an increasing number of nodal points as the modal number increases. Experimental results confirm the validity and usefulness of the cylindrical beam model of the wind chime pipes.

Acoustic transient radiation from a vibrating chime is addressed in the paper using a space-time superposition of ring sources along the axis of the chime. The ring sources are shown to result in a space-time varying force on the air in contact with the chime.  Furthermore, the force is simply related to the previously noted sum of  temporally decaying modal beam vibrations. The directional properties of the acoustic field are discussed and it is shown that the field exhibits nulls in the directions along and perpendicular to the axis of the chime.

2aSA9 – Acoustic black holes in airfoils

NRC Postdoctoral Fellow, Acoustics Division, Code 7165,
U S Naval Research Laboratory
4555 Overlook Ave SW,
Washington, DC 20375
 
Caleb F. Sieck – caleb.sieck@nrl.navy.mil
Matthew D. Guild – matthew.guild@nrl.navy.mil
Charles A. Rohde – charles.rohde@nrl.navy.mil
Acoustics Division, Code 7165,
U S Naval Research Laboratory
4555 Overlook Ave SW,
Washington, DC 20375
 
Popular version of paper 2aSA9 – “Incorporating acoustic black holes in hydrofoils”
Presented at 11.30 am on December 3, 2019
178th ASA Meeting, San Diego, California.
 
Most of us who have flown in an airplane can recall how bumpy it gets when there is ‘turbulence’. It is scary to watch wings bend the way they do, even though they are designed to withstand such bumps. However, as one can imagine, these vibrations are not desirable and affect the aircraft’s longevity and performance. When we slice an aircraft wing somewhere in between (as highlighted in the sketch below), we find that it has a unique shape, called an ‘airfoil’. This is the shape that makes the plane fly, and also, as a result, bears the brunt of turbulent air and those vibrations.
 
airfoils
 
In 1988, Mironov pointed out that vibrations that strike on one end of a beam may never make it through if the other end is tapered gradually enough all the way down to a ‘zero thickness’. In other words, those vibrations get trapped or absorbed inside forever – also known as the ‘acoustic black hole’ effect. In reality, since it isn’t possible to make an edge have zero thickness, scientists have figured out that sticking some damping material near the edge (similar to foam or rubber on furniture feet) works almost as well.
 
In this study, we explore a way this effect could help reduce those airfoil vibrations. For the airplane, only the shape on the outside of the airfoil matters, not the inside. We take advantage of this fact and show that it is possible to design an airfoil with these black holes inside, without changing either the outside shape or the total weight.
 
Shown below are three of the designs that we tested. We fix the mass of the structure and damping that we use, and redistribute them between the three cases. The first case has uniformly spread structure and damping, to represent a ‘standard’ design. We’re basically trying to improve on this. The second case has a single black hole inside along with appropriate damping, while the third case has three.
 
airfoils
 
We use some of the latest in 3d printing technology to create these complex designs. For testing them, we vibrate all three airfoils on their front edge in the same way and measure how vibrations move through the airfoil length all the way to the back edge. Shown below are the vibration levels that we measured at the rear edge over three frequency ranges. Note, lower the vibration, the better.
 
When compared with the uniform case, the sample with one black hole does 10-15% in the low and mid frequency ranges, and ~30% better in the high frequency range. The three-black hole case does almost similar (~1% worse in fact) for the low frequency range, but performs 50-65% better for higher frequencies. These results are promising and motivate us to expand our research in this direction.
 
Work sponsored by the Office of Naval Research.

3pSA – Diagnosing wind turbine condition employing a neural network to the analysis of vibroacoustic signals

Andrzej Czyzewski
Gdansk University of Technology, Multimedia Systems Department
80-233 Gdansk, Poland
www.multimed.org
e-mail: multimed.org@gmail.com

Popular version of paper 3pSA 
Presented Wednesday afternoon, December 4, 2019
178th ASA Meeting, San Diego, California

The maintenance of wind turbines sums up to approx. 20-35% of their life-cycle costs. Therefore, it is important from the economic point of view to detect damage early in the wind turbines before failures occur. For this purpose, a monitoring system was built that analyzes both acoustic signals acquired from the non-contact acoustic intensity probe, as well as from the traditional accelerometers, mounted on the internal devices in the nacelle. The signals collected in this way are used for long-term training of the neural network. The appropriately trained network automatically detects deviations, signaling them to technical service. In this way, artificial intelligence is used to automatically monitor the technical condition of wind turbines.

Existing methods are mostly based on different types of accelerometers mounted on the blades of the wind turbine or on the bearings of the electric power generator. Contactless methods we develop provide many benefits (e.g. no need to stop the wind turbine for mounting of accelerometers). The main source of acoustic signals obtained without contact is a special multi-microphone probe that we have constructed. A special feature of this solution is the ability to precisely determine the direction from which the sound is received. Thanks to this, the neural network learns non-mixed up sounds emitted by mechanisms located in various places inside the turbine. The acoustical probe is presented in Figure 1, and the device containing electronic circuits for processing acoustic signals is shown in Figure 2.

Figure 1 Acoustical probe (a) and complete acoustical vector sensor (b)

Figure 2 Device collecting vibroacoustic signals (a),

which also contains a neural network module that detects if these signals are abnormal (b).

 

In addition, we are also developing methods for visual surveillance of a wind farm, which by their nature belong to non-contact methods. We received encouraging results by amplifying the invisible vibrations in video. The method we applied is called the motion magnification in the video (invented by scientists from MIT). We used this approach for extracting information on the vibrations of the whole wind turbine construction. What comes out of this can be seen in the two short films pasted below, the first of which shows the original video image, and the second after applying the invisible pixel movements caused by vibrations and swaying of the wind turbine tower.

Video 1. Original video recording of a working wind turbine

Video 2. The same turbine as in Video 1 after applying the pixel movements magnification

Since image vibrations can be transformed into acoustic vibrations, we were able to propose a method for monitoring wind turbines using a kind of non-contact vibrometry based on video-audio technology.

The neural network depicted in Figure 3 is the so-called autoencoder. It learns to copy its inputs to its outputs prioritizing the most relevant aspects of the data to be copied. In this way, it extracts relevant data from complex signals, so it also becomes sensitive to unexpected changes in the acoustic and video data structure. Therefore, a properly trained network can be entrusted with the task of supervising a wind turbine, i.e. checking that everything is in order with it.

Figure 3 Autoencoder neural network architecture, reflecting the principle that the encoder on the left sends only a minimal amount of relevant data, and yet the decoder on the right can reproduce the same information that the entire network sees on its inputs.

The research was subsidized by the Polish National Centre for Research and Development within the project “STEO – System for Technical and Economic Optimization of Distributed Renewable Energy Sources”, No. POIR.01.02.00-00-0357/16.