Reducing Ship Noise Pollution with Structured Quarter-Wavelength Resonators

Mathis Vulliez – mathis.vulliez@usherbrooke.ca

Université de Sherbrooke, Département de génie mécanique, Sherbrooke, Québec, J1K 2R1, Canada

Marc-André Guy, Département de génie mécanique, Université de Sherbrooke
Kamal Kesour, Innovation Maritime, Rimouski, QC, Canada
Jean-Christophe G.Marquis, Innovation Maritime, Rimouski, QC, Canada
Giuseppe Catapane, University of Naples Federico II, Naples, Italy
Giuseppe Petrone, University of Naples Federico II, Naples, Italy
Olivier Robin, Département de génie mécanique, Université de Sherbrooke

Popular version of 1pEA6 – Use of metamaterials to reduce underwater noise generated by ship machinery
Presented at the 186th ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/index.php?page=Session&project=ASASPRING24&id=3669352

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

The underwater noise generated by maritime traffic is the most significant source of ocean noise pollution. This pollution threatens marine biodiversity, from large marine mammals to invertebrates. At low speeds, the machinery dominates the underwater radiated noise from vessels. It also has a precise sound signature since it usually operates at a fixed rotation frequency. If you think of it, an idling vehicle produces a tonal acoustic excitation. The sound energy distribution is mainly concentrated at a few precise frequencies and multiples. Indeed, the engine rotates at a given rotation speed – in round per minutes – or frequency (divided by 60, it is the number of oscillations per second). In addition to the rotating frequency, the firing order and the number of cylinders will lead to the generation of excitation multiples of the rotating frequency. The problem is that the produced frequencies are generally low and difficult to mitigate with classical soundproofing materials requiring substantial material thickness.

This research project delves into new solutions to mitigate underwater noise pollution using innovative noise control technologies. The solution investigated in this work is structured quarter-wavelength acoustic resonators. These resonators usually absorb sound at a resonant frequency and odd harmonics, making them ideal for targeting precise frequencies and their multiples. However, the length of these resources is dictated by the wavelength corresponding to the target frequency. As for the required material thickness, this wavelength is significant at low frequencies (in air, for a frequency of 100 Hz and a speed of sound of 340 m/s, the wavelength is 3.4 m since the wavelength is the ratio of speed by frequency). The length of a quarter wavelength resonator tuned at 100 Hz is thus 0.85 m.

Fig.1. Comparison between classical and innovative soundproofing material on sound absorption, from Centre de recherche acoustique-signal-humain, Université de Sherbrooke.

Therefore, a coiled quarter wavelength resonator was considered to reduce its bulkiness, and facilitate their installation. The inspiration follows Archimedes’ spiral geometry shape, a structure easily manufactured using today’s 3D printing technologies. Experimental laboratory tests were conducted to characterize the prototypes and determine their effectiveness in absorbing sound. We also created a numerical model that allows us to quickly answer optimization questions and study the efficiency of a hybrid solution: a rock wool panel with embedded coiled resonators. We aim to combine classic and innovative solutions tom propose low weight and compact solutions to efficiently reduce underwater noise pollution!

Fig.2. Numerical model of coiled resonators embedded in rockwool, from Centre de recherche acoustique-signal-humain, Université de Sherbrooke.

Novel audio analysis helps identify multiple sounds in forensic gunshot recordings

Steven Beck – stevendbeck@alumni.rice.edu

Beck Audio Forensics, 7618 Rockpoint Dr, Austin, Texas, 78731, United States

Popular version of 2pEA8 – Dissecting Recorded Gunshot Sounds
Presented at the 186th ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/index.php?page=IntHtml&project=ASASPRING24&id=3669350

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

Forensic audio can provide important evidence, especially when the scene information is not captured on video.  Audio recordings of gunshots often supply additional information, or the only information, from a shooting incident.  Analysis of the recorded audio can help determine who fired first, how many guns were fired, and sometimes identify each gunshot in a sequence.  The muzzle blast, or “bang”, and the ballistic shockwave, or “crack” from a supersonic bullet are the most common sounds analyzed.  These very loud sounds often obscure other gunshot sounds that can provide important forensic evidence.  New recording technology, like floating point recorders and high sensitivity police body cameras, may capture multiple acoustic sound sources from a gunshot, depending on the shooting, propagation, and recording conditions.

In order to investigate the multiple sounds from a gunshot, a body camera and Zoom F6 multi-channel floating point recorder were used to record gunshot sounds using microphones placed at 90o, 135o, and 180o relative to the line of fire.  Revolvers, semiautomatic pistols, and long barrel firearms (rifles and shotguns) are shown to have different sequences of acoustic source events:

  • Revolver have the primer blast, chamber gas jet, muzzle blast, mechanical sounds
  • Pistols have the primer blast, muzzle blast, slide/bolt sound, mechanical sounds
  • Semiautomatic rifles have primer blast, slide/bolt sound, muzzle blast, mechanical sounds
  • Bold action rifles have primer blast, muzzle blast, later mechanical sounds

Figure 1 shows an example of multiple acoustic sources in a gunshot.  The left side plots show a muzzle blast followed by a mechanical sound.  Zooming in on the amplitude shows a much quieter primer blast that occurs before the muzzle blast.  The bottom right plot is the same gunshot recorded on a police-style body camera.  The primer blast is very clear, but the other gunshot sounds are clipped.  Since the primer blast can only be recorded behind or to the side of a close-by shooter, it’s presence in a recording can help determine “who fired first” or help identify individual gunshots.

Figure 1 – A Primer Blast Prior to the Muzzle Blast Indicates the Presence of a Near-by Shooter

In addition to blast-related sounds, there are sounds related to ballistics.  Recording these sounds are very position dependent, and require the recording system to be close to the source.  These sounds include the ballistic shockwave and ballistic flow sound (recorded close to a passing bullet), tumbling bullet, reverberation and reflections, and the ballistic impact.  Ballistic sounds can help identify a gunshot or a possible shooting location.

A general method to obtain clearer images at a higher resolution than theoretical limit

Jian-yu Lu – jian-yu.lu@ieee.org
X (Twitter): @Jianyu_lu
Instagram: @jianyu.lu01
Department of Bioengineering, College of Engineering, The University of Toledo, Toledo, Ohio, 43606, United States

Popular version of 1pBAb4 – Reconstruction methods for super-resolution imaging with PSF modulation
Presented at the 186 ASA Meeting
Read the abstract at https://eppro02.ativ.me/web/index.php?page=IntHtml&project=ASASPRING24&id=3675355

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

Imaging is an important fundamental tool to advance science, engineering, and medicine, and is indispensable in our daily life. Here we have a few examples: Acoustical and optical microscopes have helped to advance biology. Ultrasound imaging, X-ray radiography, X-ray computerized tomography (X-ray CT), magnetic resonance imaging (MRI), gamma camera, single-photon emission computerized tomography (SPECT), and positron emission tomography (PET) have been routinely used for medical diagnoses. Electron and scanning tunneling microscopes have revealed structures in nanometer or atomic scale, where one nanometer is one billionth of a meter. And photography, including the cameras in cell phones, is in our everyday life.

Despite the importance of imaging, it was first recognized by Ernest Abbe in 1873 that there is a fundamental limit known as the diffraction limit for resolution in wave-based imaging systems due to the diffraction of waves. This effects acoustical, optical, and electromagnetic waves, and so on.

Recently (see Lu, IEEE TUFFC, January 2024), the researcher developed a general method to overcome such a long-standing diffraction limit. This method is not only applicable to wave-based imaging systems such as ultrasound, optical, electromagnetic, radar, and sonar; it is in principle also applicable to other linear shift-invariant (LSI) imaging systems such as X-ray radiography, X-ray CT, MRI, gamma camera, SPECT, and PET since it increases image resolution by introducing high spatial frequencies through modulating the point-spread function (PSF) of an LSI imaging system. The modulation can be induced remotely from outside of an object to be imaged, or can be small particles introduced into or on the surface of the object and manipulated remotely. The LSI system can be understood with a geometric distortion corrected optical camera in the photography, where the photo of a person will be the same or invariant in terms of the size and shape if the person only shifts his/her position in the direction that is perpendicular to the camera optical axis within the camera field of view.

Figure 1 below demonstrates the efficacy of the method using an acoustical wave. The method was used to image a passive object (in the first row) through a pulse-echo imaging or to image wave source distributions (in the second row) with a receiver. The best images obtainable under the Abbe’s diffraction limit are in the second column, and the super-resolution (better than the diffraction limit) images obtained with the new method are in the last column. The super-resolution images had a resolution that was close to 1/3 of the wavelength used from a distance with an f-number (focal distance divided by the diameter of the transducer) close to 2.

Figure 1. This figure was modified in courtesy of IEEE (doi.org/10.1109/TUFFC.2023.3335883).

Because the method developed is based on the convolution theory of an LSI system and many practical imaging systems are LSI, the method opens an avenue for various new applications in science, engineering, and medicine. With a proper choice of a modulator and imaging system, nanoscale imaging with resolution similar to that of a scanning electron microscope (SEM) is possible even with visible or infrared light.

Determination of the sound pressure level in fitness studios

Max Brahman – max.brahman@getzner.com

1/2-22 Kirkham Road West, Keysborough, Melbourne, victoria, 3173, Australia

Ulrich Gerhaher
Helmut Bertsch
Sebastian Wiederin

Popular version of 4pEA7 – Bringing free weight areas under acoustic control
Presented at the 185th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0023540

Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.

In fitness studios, the ungentle dropping of weights, such as heavy dumbbells at height of 2 meters, is part of everyday life. As the studios are often integrated into residential or office buildings, the floor structures must be selected in such a way that impact energy is adequately insulated to meet the criteria for airborne noise in other parts of the building. Normally accurate prediction of the expected sound level for selection of optimal floor covering, can only be achieved through extensive measurements and using different floor coverings on site.

To be able to make accurate predictions without on-site measurements, Getzner Werkstoffe GmbH carried out more than 300 drop tests (see Figure 1) and measured the ceiling vibrations and sound pressure level in the room below. Dumbbells weighing 10 kg up to packages of 100 kg were dropped from heights of 10 cm up to 160 cm. This covers the entire range of dumbbells drops, approximately, to heavy barbells. collection of test results is integrated into a prediction tool
developed by Getzner.

The tested g-fit Shock Absorb superstructures consist of 1 to 3 layers of PU foam mats with different dynamic stiffnesses and damping values. These superstructures are optimized for the respective area of application: soft superstructures for low weights or drop heights and stiffer superstructures for heavy weights and high drop heights to prevent impact on the subfloor. The high dynamic damping of the materials reduces the rebound of the dumbbells to prevent injuries.

Heat maps of the maxHold values of the vibrations were created for each of the four g-fit Shock Absorb superstructures and a sports floor covering (see Figure 2). This database can now be used in the prediction tool for two different forecasting approaches.

Knowing the dumbbell weight and the drop height, the sound pressure level can be determined for all body variants for the room below, considering the ceiling thickness using mean value curves. No additional measurement on site is required. Figure 3 shows measured values of a real project vs. the predicted values. The deviations between measurement and prediction tool are -1.5 dB and 4.6 dB which is insignificant. The improvement of the setup (40 mm rubber granulate sports flooring) is -9.5 dB for advanced version and -22.5 dB for pro version of g-fit shock absorb floor construction.

To predict the sound pressure level in another room in the building, sound level should be measured for three simple drops in the receiver room using a medium-thickness floor structure. Based on these measured values and drop tests database, the expected frequency spectrum and the sound pressure level in the room could then be predicted.

The tool described makes it easier for Getzner to evaluate the planned floor structures of fitness studios. The solution subsequently offered enables compliance with the required sound insulation limits.

Figure 1, Carrying out the drop tests in the laboratory.
Figure 2, Maximum value of the ceiling vibration per third octave band as a function of the drop energy
Figure 3, measured and predicted values of a CrossFit studio, on the left only sports flooring without g-fit Shock Absorb, in the middle with additional g-fit Shock Absorb advanced and on the right with gfit Shock Absorb pro, dumbbell weights up to 100 kg

Solar-Powered Balloons Detect Mysterious Sounds in the Stratosphere #ASA184

Solar-Powered Balloons Detect Mysterious Sounds in the Stratosphere #ASA184

Inexpensive and easy to build, data collecting balloons capture low-frequency sound in the Earth’s atmosphere.

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

CHICAGO, May 11, 2023 – Imagine if sending your science experiment 70,000 ft in the air just took painter’s plastic, tape, a dash of charcoal dust, and plenty of sunlight.

Inflating a solar hot air balloon with an infrasound microbarometer payload. Photo credits: Darielle Dexheimer, Sandia National Laboratories.

Daniel Bowman of Sandia National Laboratories will present his findings using solar-powered hot air balloons to eavesdrop on stratospheric sounds at the upcoming 184th Meeting of the Acoustical Society of America, running May 8-12 at the Chicago Marriott Downtown Magnificent Mile Hotel. His presentation will take place Thursday, May 11, at 2:50 p.m. Eastern U.S. in the Purdue/Wisconsin room at the Chicago Marriott Downtown Magnificent Mile Hotel.

The stratosphere is a relatively calm layer of Earth’s atmosphere. Rarely disturbed by planes or turbulence, microphones in the stratosphere pick up a variety of sounds unheard anywhere else. This includes natural sounds from colliding ocean waves and thunder, human-created sounds like wind turbines or explosions, and even sounds with unknown origins.

To reach the stratosphere, Bowman and his collaborators build balloons that span 6 to 7 meters across. Despite their large size and data collection capability, the balloons are relatively simple.

“Our balloons are basically giant plastic bags with some charcoal dust on the inside to make them dark. We build them using painter’s plastic from the hardware store, shipping tape, and charcoal powder from pyrotechnic supply stores.  When the sun shines on the dark balloons, the air inside heats up and becomes buoyant. This passive solar power is enough to bring the balloons from the surface to over 20 km (66,000 ft) in the sky,” said Bowman. “Each balloon only needs about $50 worth of materials and can be built in a basketball court.”

The researchers collect data and detect low-frequency sound with microbarometers, which were originally designed to monitor volcanoes. After releasing the balloons, they track their routes using GPS – a necessary task since the balloons sometimes sail for hundreds of miles and land in hard-to-reach places. But, because the balloons are inexpensive and easy to construct and launch, they can release a lot of balloons and collect more data.

Along with the expected human and environmental sounds, Bowman and his team detected something they are not able to identify.

“[In the stratosphere,] there are mysterious infrasound signals that occur a few times per hour on some flights, but the source of these is completely unknown,” said Bowman.

Solar-powered balloons could also help explore other planets, such as observing Venus’ seismic and volcanic activity through its thick atmosphere.

———————– MORE MEETING INFORMATION ———————–
Main meeting website: https://acousticalsociety.org/asa-meetings/
Technical program: https://eppro02.ativ.me/web/planner.php?id=ASASPRING23&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
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/.

Small but Mighty: Insect-Inspired Microphones #ASA184

Small but Mighty: Insect-Inspired Microphones #ASA184

3D printing technology facilitates bio-inspired microphones that operate autonomously and efficiently.

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

CHICAGO, May 10, 2023 – What can an insect hear? Surprisingly, quite a lot. Though small and simple, their hearing systems are highly efficient. For example, with a membrane only 2 millimeters across, the desert locust can decompose frequencies comparable to human capability. By understanding how insects perceive sound and using 3D-printing technology to create custom materials, it is possible to develop miniature, bio-inspired microphones.

The displacement of the wax moth Acroia grisella membrane, which is one of the key sources of inspiration for designing miniature, bio-inspired microphones. Credit: Andrew Reid

Andrew Reid of the University of Strathclyde in the U.K. will present his work creating such microphones, which can autonomously collect acoustic data with little power consumption. His presentation, “Unnatural hearing — 3D printing functional polymers as a path to bio-inspired microphone design,” will take place Wednesday, May 10, at 10:05 a.m. Eastern U.S. in the Northwestern/Ohio State room, as part of the 184th Meeting of the Acoustical Society of America running May 8-12 at the Chicago Marriott Downtown Magnificent Mile Hotel.

“Insect ears are ideal templates for lowering energy and data transmission costs, reducing the size of the sensors, and removing data processing,” said Reid.

Reid’s team takes inspiration from insect ears in multiple ways. On the chemical and structural level, the researchers use 3D-printing technology to fabricate custom materials that mimic insect membranes. These synthetic membranes are highly sensitive and efficient acoustic sensors. Without 3D printing, traditional, silicon-based attempts at bio-inspired microphones lack the flexibility and customization required.

“In images, our microphone looks like any other microphone. The mechanical element is a simple diaphragm, perhaps in a slightly unusual ellipsoid or rectangular shape,” Reid said. “The interesting bits are happening on the microscale, with small variations in thickness and porosity, and on the nanoscale, with variations in material properties such as the compliance and density of the material.”

More than just the material, the entire data collection process is inspired by biological systems. Unlike traditional microphones that collect a range of information, these microphones are designed to detect a specific signal. This streamlined process is similar to how nerve endings detect and transmit signals. The specialization of the sensor enables it to quickly discern triggers without consuming a lot of energy or requiring supervision.

The bio-inspired sensors, with their small size, autonomous function, and low energy consumption, are ideal for applications that are hazardous or hard to reach, including locations embedded in a structure or within the human body.

Bio-inspired 3D-printing techniques can be applied to solve many other challenges, including working on blood-brain barrier organoids or ultrasound structural monitoring.

———————– MORE MEETING INFORMATION ———————–
Main meeting website: https://acousticalsociety.org/asa-meetings/
Technical program: https://eppro02.ativ.me/web/planner.php?id=ASASPRING23&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
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/.