bluuebunny/crossref_metadata_2025 huggingface dataset:
Old meets new: 3-D printing and the art of violin-making
Authors: Brown Mary-Elizabeth
Published: November 2022

Since violin-making emerged in the early 16th century, luthiers have incorporated new technology and scientific principles into their craft in an effort to create different sounds, increase resonance, amplify volume, and create more ease of playing. In late 2018, a Canadian interdisciplinary team spearheaded by the Ottawa Symphony Orchestra asked the question: What happens when you transpose those same principles to the 21st-century? In this session, participants will hear the story of the 3-D printed instruments that made international news from the perspective of the lead musician on the team, discover the manufacturing iterations and materials that led to the final versions used in the premiere of the first-ever concerto written for 3-D printed instruments and symphony orchestra, and explore the sound concepts behind these instruments as the centuries-old tradition of violinmaking meets 21st century technology. Join us as we delve into the juncture of old and new, examine the results of such interdisciplinary work and look to the future of 3-D printing in the realm of classical music and beyond.
The impact on speech with different deep brain stimulation settings in Parkinson's disease
Authors: Wang Emily Q. , Mullen Maura , Karl Jessica A. , Verhagen Metman Leonard A.
Published: November 2022

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized by the progressive degeneration of the nigrostriatal dopaminergic pathway which affects movement initiation and maintenance, causing hypokinetic dysarthria in PD. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been widely used to manage rigidity, bradykinesias and drug-induced dyskinesias. While STN DBS successfully manages many symptoms of PD, speech response has been widely reported as “no or negative impact”. The High-Frequency Setting (HFS) is more focused within the STN which is known to control appendicular symptoms. However, the unintentional HFS current spreading to adjacent brain areas, such as the corticospinal and corticobulbar tracts, was thought to contribute to the deterioration of axial symptoms, including speech. The Low-Frequency Setting (LFS) extends more dorsally and ventrally towards surrounding structures, hence does not show the same negative impact and may reduce the negative impact on the axial functions including speech. This double-blind, randomized perception study assesses the impact of two deep brain stimulation (DBS) settings (high-frequency stimulation and interleave-interlink dual-frequency paradigm) on speech produced by 20 patients with PD. The impact of the two testing conditions was different for different Syllable Types with significant negative correlation between the articulatory rate and articulatory accuracy.
Lexical effects on talker discrimination in adult cochlear implant users
Authors: Tamati Terrin N. , Jebens Almut , Baskent Deniz
Published: November 2022

The lexical and phonological content of an utterance impacts the processing of talker-specific details in normal-hearing (NH) listeners. For example, previous research has shown that NH listeners display stronger perception of talker-specific details for real words compared to nonwords, and for nonwords with high phonotactic probability compared to nonwords with low phonotactic probability. For adult cochlear implant (CI) users, limitations in the talker-specific details conveyed by their devices may alter the reliance on lexical information in talker discrimination. The current study examined the impact of lexical content on talker discrimination in adult CI users. In a same-different talker discrimination task, word pairs – produced either by the same or different talkers – were either lexically easy (high frequency, low neighborhood density) or lexically hard (low frequency, high neighborhood density). Results showed a significant interaction between lexical content and talker pair. For same-talker pairs, accuracy was higher for lexically easy words than lexically hard words. For different-talker pairs, accuracy was higher for lexically hard words than lexically easy words. Despite limitations in talker discrimination, these preliminary results suggest that adult CI users use lexical information in the processing of talker-specific details, and additionally may rely less on acoustic-phonetic details when processing is easy.
Loudness and rate perception in Parkinson's disease
Authors: Heffner Christopher C. , Tjaden Kris , Mercado Eduardo
Published: November 2022

In speech communication, Parkinson’s disease (PD) is typically discussed in terms of its production consequences. However, a small but growing literature indicates that PD may also result in deficits in the perception of loudness and rate information in speech. In the present study, we focus on the extent to which the perceptual deficits in PD are limited to speech or shared with other modalities, and the degree to which these deficits are dependent solely on perception or are also found in tasks of learning. To assess these questions, people with PD and age-matched controls perform two tasks: an AXB task of speech rate or intensity discrimination, and a simple learning task testing participants’ ability to group versions of a sentence based on their rate or intensity properties. For the AXB task, participants perform three additional versions of the task with stimuli that vary in their speech-like properties: time-reversed speech, pure tones, or visualizations. Preliminary data indicates that for control participants, all the continua are discriminated at above-chance performance and that participants can learn to group sentences based on both rate and intensity. Performance for the people with Parkinson’s Disease displays a great deal of variability.
Machine learning based estimation of hoarseness severity from sustained vowels
Authors: Schraut Tobias , Schützenberger Anne , Arias-Vergara Tomas , Kunduk Melda , Echternach Matthias , Döllinger Michael
Published: November 2022

Acoustic assessment of voice impairment is commonly performed by subjective perceptual evaluation of continuous speech based on a grading system such as the roughness, breathiness, hoarseness (RBH) scale. Here, we present an automatic approach to objectively quantify hoarseness severity based on sustained vowels. For this study, a total of 635 recordings of the sustained vowel /a/ were collected. Temporal, spectral and cepstral features were extracted from one second of each recording. All recordings have an assigned RBH value, which was determined subjectively by an expert based on continuous speech of the respective subject. In order to account for the label noise introduced by different valuation bases, subjects were divided into two levels of hoarseness H < 2 and H ≥ 2. Logistic Regression was employed as classification model, using the resulting output probabilities as continuous severity rating. Relevant features were selected using a sequence of filter methods and backward elimination. The original feature set was reduced from 50 to 5 features. A classification accuracy of 86.73% was achieved on the test set. Detailed evaluation of output probabilities shows strong correlation (r = 0.81) with H values, allowing to capture and quantify individual improvement, deterioration or no change of hoarseness at different points in time, e.g. before and after voice therapy. The presented method describes a promising approach for objective evaluation of hoarseness, allowing to quantify treatment progress for patients with voice disorders.
Manifold learning for dynamic array geometries
Authors: Sarkar Kanad , Mittal Manan , Corey Ryan M. , Singer Andrew C.
Published: November 2022

Large-scale distributed arrays can obtain high spatial resolution, but they typically rely on a rigid array structure. If we want to form distributed arrays from mobile and wearable devices, our models need to account for motion. The motion of multiple microphones worn by humans can be difficult to track, but through manifold techniques we can learn the movement through its acoustic response. We show that the mapping between the array geometry and its acoustic response is locally linear and can be exploited in a semi-supervised manner for a given acoustic environment. We will also investigate generative modelling of microphone positions based on their acoustic response to both synthetic and recorded data. Prior work has shown a similar locally linear mapping between source locations and their spatial cues, and we will attempt to combine these findings with our own to develop a localization model suitable for dynamic array geometries.
One track, two experiments four years apart: On the repeatability of geoacoustic inversion on the New England Mud Patch
Authors: Bonnel Julien , Dosso Stan , McNeese Andrew R. , Wilson Preston S.
Published: November 2022

Our current knowledge of the geoacoustic properties of the New England Mud Patch (NEMP) is mostly driven by data collected in 2017 as part of the Seabed Characterization Experiment (SBCEX17). In 2021, a modest geoacoustic inversion experiment was performed on the NEMP using a simple and low-cost pair of experimental assets: a “TOSSIT” passive acoustic mooring and an impulsive “RIUSS” (Rupture Induced, Underwater Sound Source). The TOSSIT/RIUSS data were collected on a track that was studied intensively during SBCEX17, but with fundamental differences in oceanographic conditions: a frontal intrusion was present at the experimental site in 2021, creating a strongly stratified sound speed profile (SSP) in the water column, while the water column was essentially iso-speed in 2017. The 2021 TOSSIT/RIUSS data are used to perform geoacoustic inversion using warping and Bayesian trans-dimensional methods. The geoacoustic properties estimated for the 2021 data compare favorably to results obtained with SBCEX17 data, even when the 2021 data are inverted jointly for water-column SSP and seabed parameters. This study demonstrates inversion repeatability on the NEMP using data sets collected years apart and under different (and potentially unknown) oceanographic conditions. [Work supported by the Office of Naval Research.]
Broadband acoustic wave propagation in temporally variable range dependent shallow water environment
Authors: Badiey Mohsen , Wan Lin , Castro-Correa Jhon A. , Escobar-Amado Christian D.
Published: November 2022

Broadband acoustic wave propagation in shallow water regions involves interactions with the sea surface, sea bottom, and the water column. The topic of shallow water acoustics in the presence of variable water column has been of interest in recent years. Experimental observations have shown the importance of the effects due to the boundaries and the sound speed profile in the water column. However, more work needs to be done to establish ground truth in numerical modeling for temporally variable water column in a range dependent environment. In this paper we examine the broadband propagation on the shelf as well as the range dependent shelf break regions to depict how temporal variability of sound speed could change the dispersion characteristics of the broadband signal. Comparison between modeled and experimental data are provided. [Work supported by ONR OA program.]
Acoustic modeling of ducted propagation in the New England Mud Patch
Authors: Lopez Case Jade F. , McNeese Andrew R. , Wilson Preston S. , Miller James H. , Potty Gopu R.
Published: November 2022

Experiments were conducted on the New England Mud Patch in 2017, 2021, and 2022. The 2017 Seabed Characterization Experiment (SBCEX17) utilized Signal Underwater Sound (SUS) charges, model Mk64, to produce an impulsive acoustic waveform. However, recent work in 2022 has additionally utilized the Rupture Induced Underwater Sound Source (RIUSS) to produce a high-amplitude, broadband waveform with minimal bubble oscillations. Results from these experiments suggested the presence of a surficial layer of mud with a sound speed lower than that of the underlying mud and overlying water. The SBCEX22 experiment included the deployment of nine RIUSS devices and the use of Ocean Bottom Recorders (OBX) to measure the acoustic pressure and three components of particle velocity at range of about 1 km. Conductivity, temperature, and depth measurements from CTD surveys were taken from several locations around the mud patch and used to generate sound speed profiles. These were input into the RAM parabolic equation model to analyze the effect of the sound speed in mud on propagation. Results from the RAM modeling indicates that at mid-frequencies (1-3 kHz) the lower sound speed at the top of the mud layer creates a duct where the transmission loss is reduced.
LF electronic Architecture—Saving cost and adding acoustic flexibility in the construction of multi-purpose performing arts facilities
Authors: Barbar Steve
Published: November 2022

Over the course of many years, we have successfully integrated LF components into full range electronic architecture installations. These components are typically utilized when programming includes acoustic instruments such as pipe organ, or a large orchestra (or both)—or when electronic sources producing LF energy (such as effects mapping or film screening) need to be considered. However, we have also installed LF only EA systems in several concert halls in order to optimize LF performance without the high cost associated with brick and mortar construction methods. Electronic Architecture provides the added benefit of variability necessary for multi-purpose performing arts venues.
Electronic Architecture—Solutions for archetypal coupled spaces
Authors: Barbar Steve
Published: November 2022

We will discuss solutions for the most common coupled spaces in performing arts facilities—Balconies and Stages. While there are exceptions, seats in balcony and under balcony spaces sometimes have less than ideal listening conditions. For electronic and close miked sources, supplemental sound reinforcement can help to provide expected perception of the direct sound. However, perceived acoustical conditions do not match that of the main volume; the sense of engagement is compromised. Electronic Architecture incorporated in these spaces can dramatically improve listening uniformity. Additionally, the loudspeaker array can be used for supplemental sound reinforcement including film surround sound. Many multi-purpose performing arts venues do not have resources to procure, deploy, strike, or store an architectural stage shell system. A virtual shell is far more cost effective, requires less time and manpower to set up or strike, and requires far less storage space. In addition, it provides far greater acoustic variability—accommodating a wider range of performances.
How real is Virtual Acoustics?
Authors: Vorlaender Michael , Aspoeck Lukas
Published: November 2022

Recent comparisons of room-acoustic simulations and auralizations demonstrated that a high degree of realism can be achieved under certain conditions. How close the simulation can get to reality depends on the definition of the objective in general terms (authenticity or plausibility). The question is also what is the application scenario of the simulation. The goal can be to create an exact replica of a real space, a blind simulation of a future or lost space, or a demonstration of consequences of decisions during a design process. This work discusses the sources of uncertainties in Virtual Room Acoustics, the effort to be taken for achieving high realism, and suggestions for use of Virtual Acoustics in practice.
Sound propagation and scattering in turbulent media
Authors: Ostashev Vladimir E. , Wilson D. Keith
Published: November 2022

This presentation overviews sound propagation and scattering in turbulent media and pertinent acoustic remote sensing of turbulence. Although sound propagation through a turbulent atmosphere is mainly considered, the presented results apply to other media such as oceanic turbulence. Formulations are provided for various statistical characteristics of acoustic signals such as the scattering cross section, the variances of the phase and log-amplitude fluctuations, the spatial, temporal, and cross-frequency coherences, and the probability density functions. Monte Carlo simulation of sound propagation in a random medium is explained. Specifics of acoustic signals in turbulent media as compared to electromagnetic waves are highlighted. For example, sound waves are scattered by both the sound speed and medium velocity fluctuations, which are scalar and vector random fields, respectively, with different statistical properties. Also, fluctuations in the acoustic refractive index are much stronger than those in electromagnetic propagation, and sound can be scattered by humidity (or salinity) fluctuations. Finally, the Markov approximation, which is widely used for electromagnetic waves, might not be applicable for some statistical characteristics of acoustic signals. It is explained how these specifics of sound propagation are addressed in atmospheric acoustics.
How prevalent is acoustic scattering from oceanic microstructure?
Authors: Lavery Andone C. , Bassett Christopher , Loranger Scott
Published: November 2022

Any oceanic environment with spatial gradients in sound speed and density can result in acoustic scattering hot spots. These acoustic hotspots can be rapidly evolving and vary in their spatial heterogeneity. Here, we review acoustic scattering models for turbulence and present data collected with a variety of split-beam and multi-beam echosounders illustrating the range of environments and spatial scales associated with scattering from physical microstructure, including shear instabilities in estuarine environments, non-linear internal waves on the continental shelf, strong interface scattering due to double-diffusion, scattering from strong gradients or interfaces, and turbulent microstructure at the New England shelf break front. The theoretical acoustic scattering formulations for different types of physical microstructure are applied to these different environments, and recommendations are made for optimal frequency bands to sample the different types of physical microstructure and the optimal measurements for inference of parameters that describe the physical microstructure. Limitations imposed on detection and quantification of scattering from the physical microstructure due to sources including suspended sediment, bubbles, and biological targets, are also discussed. [Work supported by the ONR.]
Acoustic coupling pads for the control of ultrasound neuromodulation exposure
Authors: Schafer Samantha , Schafer Mark
Published: November 2022

We have developed acoustic coupling pads that facilitate single-blind and double-blind neuromodulation experiments by selectively transmitting ultrasound without affecting the audible sound. The pads were made from a skin-safe two-part silicone with little to no ultrasonic attenuation, that also provided the necessary acoustic properties, stability and flexibility. To inhibit the transmission of ultrasound, a foam disk was imbedded into the pad during the manufacturing process. The design goal for acoustic attenuation was −40 dB. 20 sets of transmit pads and non-transmit pads were fabricated. Acoustic transmission loss was measured in a water tank with a 60 mm diameter, 80 mm focus circular disk transducer operated at 650 kHz and a standard hydrophone (Reson TC4038). Transmit pads had an average of −0.4 dB loss; non-transmit pads met the required −40 dB loss (average: −47.4 dB). An operator experienced with ultrasound treatments was unable to distinguish them by visual inspection or casual physical manipulation. An experienced subject exposed to a typical treatment regimen was not able to distinguish any audible difference. The acoustic coupling pads create identical testing situations for single-blind and double-blind studies for neuromodulation treatments so that neither the patient nor the operator administering the treatment can distinguish which patient group received the ultrasound treatment and which did not.
Higher-order perturbative parabolic-equation solutions for reduced-order sound propagation modeling
Authors: Lin Ying-Tsong
Published: November 2022

The parabolic-equation (PE) approximation to the Helmholtz equation has been shown to be one of the most effective and efficient numerical methods for sound propagation modeling. In this talk, a recursive and iterative algorithm will be introduced to compute the PE solutions due to perturbations in the medium wavenumber, which is a function of frequency and sound speed. This algorithm is developed based on perturbation theory with higher-order nonlinear terms, and it can efficiently compute higher-order derivatives of the sound pressure field with respect to changes in the local wavenumber. This higher-order perturbative PE (HOPPE) method can eventually lead to model order reduction for sound propagation simulations. An example of broadband computations with nonlinear interpolations between sampled frequencies will be presented to demonstrate the application of reduced-order modeling. A sensitivity kernel with higher-order nonlinear terms will also be introduced. Applications to data assimilation modeling and sensitivity tracking will be discussed. [Work supported by the Office of Naval Research.]
Non-intrusive mode based analyses to predict uncertainty in sound propagation in the ocean
Authors: Coelho Emanuel F. , Hursky Paul , Heaney Kevin D.
Published: November 2022

Ocean dynamics can result in significant sound speed variability that are not well captured by deterministic numerical models and can impact differently high to low frequency acoustic propagation and bottom interactions by constraining horizontal and vertical paths. Uncertainty in the sound speed can, therefore, cause inaccuracies in acoustic based tactical decision tools and severely impact the accuracy of algorithms using sound propagation to estimate ocean volume states (e.g., ocean tomography or data assimilation). In this work, we propose to use a non-intrusive Reduced Order Modelling solution that consists of building a dictionary of static modes from historical ocean simulations with different settings and resolutions and climatology to derive an expedite uncertainty model along a central deterministic forecast. The system will then, through Orthogonal Matching Pursuit along the dictionary, use the available ocean model-data mismatches and/or acoustic innovations (e.g., arrival numbers and times, acoustic energy distribution, etc.) to define an ensemble of possible sound speed volume distributions and associated acoustic propagation outcomes. We will show results using a simplified simulation experiment that extracts “observations” from a nature reference field to document the procedure and benchmark results to reconstruct 3D sound speed fields from ocean-acoustic measurements.
Efficient reversible-jump Markov-chain Monte Carlo sampling in trans-dimensional Bayesian geoacoustic inversion
Authors: Dosso Stan
Published: November 2022

This paper considers efficient computational approaches to estimate the posterior probability density (PPD) of seabed geoacoustic profiles in the Bayesian inversion of ocean acoustic data, a numerically intensive problem. Trans-dimensional (trans-D) inversion is applied, which samples probabilistically over an unknown number of seabed layers as well as the layer geoacoustic properties and parameters of the error model (variances and autoregressive coefficients). Sampling is based on the reversible-jump Markov-chain Monte Carlo algorithm, the efficiency of which depends strongly on the formulation of the proposal density by which new candidate models are generated for probabilistic acceptance/rejection. A highly efficient proposal density is presented which combines principal-component (PC) reparameterization with parallel tempering. PC reparameterization applies an adaptive linearized approximation to the PPD as the proposal density, which provides effective directions and length scales for model perturbations in high-dimensional parameter spaces. Parallel tempering considers a series of interacting Markov chains with successively relaxed likelihood functions, which greatly improves the sampling of multi-modal parameter spaces and trans-D transitions. These approaches are combined by computing different PC reparameterizations for each Markov chain in the parallel tempering formulation. Inversion results are presented as marginal probability profiles for geoacoustic properties, marginalized over the number of layers.
On the use of machine learning for ray-based ocean acoustic tomography
Authors: Sabra Karim G. , Jin Jihui , Saha Priyabrata , Durofchalk Nicholas , Romberg Justin , Mukhopadhyay Saibal
Published: November 2022

Underwater sound propagation is primarily driven by a non-linear forward model relating variability of the ocean sound speed profile (SSP) to the acoustic observations (e.g., eigenray arrival times). Ocean acoustic tomography (OAT) methods aim at reconstructing SSPs variations (with respect to a reference environment) from changes of the acoustic measurements between multiple source-receiver pairs. We investigated the performance of three different OAT methods: (1) model-based methods (i.e., classical ray-based OAT using a linearized forward model), (2) data-driven methods (such as deep learning) to directly learn the inverse model, and (3) a hybrid solution (i.e., the Neural Adjoint-NA- method) which combines deep learning of the forward model followed by a standard recursive optimization to estimate SSPs. Additionally, synthetic SSPs were generated to augment the variability of the training set. We tested these methods with modeled ray arrivals calculated for a downward refracting environment with mild fluctuations of the thermocline using idealized towed and fixed source configurations. Results indicate that merging data-driven and model-based methods can benefit OAT predictions depending on the selected sensing configurations and actual ray coverage of the water column. But ultimately, the robustness of the OAT predictions depends on the actual dynamics of the SSP variations.
Analysis of an acoustic propagation model for sources of noise with directivity in indoor environments
Authors: Campbell Steven C. , Wall Alan T. , Mobley Frank S. , Rasband Reese D. , Gee Kent L.
Published: November 2022

Small caliber firearm (SCF) noise sources are typically impulsive in nature, possess a large amount of acoustic energy (consequently a large hearing damage risk), and are not omnidirectional. These sources are often operated in indoor shooting ranges where the potential for noise exposure risk is greater due to the reflective surfaces in the room. Indoor sound propagation models require inputs such as geometry, wall material properties, and some quantified source level description. One such room acoustic modeling technique is the Image-Source Method (ISM). ISM typically assumes specular reflections off the walls and represents those reflections as image sources. Many ISM algorithms can operate with high computational efficiency for simple omnidirectional source models, usually represented by a single quantity: sound power. However, ISM models using an omnidirectional source assumption can produce high errors in some scenarios involving highly directional sources, such as SCFs. In this work, an ISM algorithm has been modified to predict listener exposure levels from non-omnidirectional sources in complicated room designs, and has been validated against measured data from an SCF on an indoor Air Force shooting range.
Assessing effect of ground reflections on gunshot noise exposure
Authors: Sorrell Avery K. , Smith Jacob R. , Gee Kent L. , Rasband Reese D. , Campbell Steven C. , Wall Alan T.
Published: November 2022

Investigation of weapons noise exposure outdoors necessitates including the impact of ground reflections. When analyzing the reflections’ impact on A-weighted equivalent level (LAeq), the contribution of the reflected waveform to the total level can often be acceptably modeled using a Friedlander equation-based source model and an ideal reflection based on the measurement geometry. However, the Friedlander model does not adequately model the negative phase of a gunshot waveform, making it inaccurate for locations where the waveform of the direct blast and the waveform of the reflection begin to overlap temporally. This merging of the waveforms for locations where the direct and ground-reflected path length difference is relatively small also makes it difficult to separate the waveforms and calculate the reflected wave’s contribution to noise exposure. As such, this paper investigates different approaches to estimating the contribution of the ground reflected wave to the LAeq, using direct and reflected waveforms in regions where they are well separated and then adjusting timing and amplitude for different geometries where merging takes place. Results reveal regions where the ground reflection contributes negligibly or even negatively to the total LAeq, which is not predicted by the Friedlander model nor by simple energy-addition approaches. [Work supported by Air Force Research Laboratory through Ball Aerospace Technology Corporation.]
Comparisons of auditory risk metrics with suppressed and unsuppressed civilian firearms
Authors: Murphy William J. , Flamme Gregory , Tasko Stephen M. , Finan Donald S. , Meinke Deanna K. , Lankford James E. , Stewart Michael
Published: November 2022

The assessment of the risk posed by firearm noise is complicated by the divergence in the allowable numbers of rounds (ANORs) returned by the available damage-risk criteria (DRCs) for impulsive noises. The ANORs returned by DRCs are strongly correlated but wide differences exist in absolute ANORs. Some firearms have suppressors and/or discharge low-velocity ammunition, both of which increase the ANORs. The extent to which suppressors and low-velocity ammunition alter the relationships among ANORs has not been determined. In this presentation, we present ANORs across many DRCs for 14 civilian firearms (3 handguns, 10 rifles, 1 shotgun) as a function of suppressor and ammunition. Results will be compared against DRC correlations observed across 54 unsuppressed firearm conditions.
When is a firearm suppressor like a hearing protector?
Authors: Tasko Stephen M. , Murphy William J. , Flamme Gregory , Deiters Kristy K. , Finan Donald S. , Meinke Deanna K. , Lankford James E. , Stewart Michael
Published: November 2022

High-level impulse noise exposure from small caliber firearms presents a significant risk of noise induced hearing loss (NIHL) for an unprotected ear. The most common method to reduce the level of noise is to provide hearing protection to both the shooter(s) and potential observers such as firing range instructors or bystanders. Not all hunters and shooters consistently use correctly fit hearing protection. Firearm suppressors provide an engineering noise control that can mitigate a significant portion of the NIHL risk. In this paper, potential analyses for the noise reduction of a firearm suppressor will be presented. The impulse insertion loss as a function of the measurement analysis time window for A-weighted, C-weighted, and unweighted sound pressure levels will be presented. This approach will be contrasted with the ANSI S12-42 standard for measuring impulse peak insertion loss for hearing protection devices.
Proposed updates for ANSI/ASA S12.42 impulsive noise test methods
Authors: Fackler Cameron J. , Murphy William J. , Gauger Dan , Berger Elliott H.
Published: November 2022

ANSI/ASA S12.42-2010 contains the first standardized test method for measuring the performance of hearing protection devices (HPDs) with high-level impulsive noise. This standard defines the impulsive peak insertion loss (IPIL) as a time-domain metric that quantifies the reduction in peak sound pressure level provided by an HPD for impulsive noises. However, IPIL as defined in S12.42-2010 is dependent on the spectrum of the impulsive noise source used for measurements of HPDs. Recent studies of HPDs with impulsive noise have led to the investigation of frequency-domain metrics and calculation methods. Using frequency-domain calculations allows IPIL to be computed for a wide range of impulsive noises, not only those used for the measurement. Consequently, significant revisions to S12.42 are under consideration. This presentation highlights select proposals including: definition and calculation of the frequency-dependent impulsive insertion loss, incorporation of frequency-domain aspects such as bone-conduction limits to attenuation, and redefinition of IPIL to be calculated from the impulsive insertion loss.
Silencing a free field blast simulator to meet residential standards
Authors: Harvey Scott B.
Published: November 2022

The Naval Medical Research Center in Silver Spring, Maryland, plans to install a new free field blast simulator in an existing building on campus. The new blast simulator will be an addition to two current blast simulators and is capable of generating higher dynamic pressure levels, up to 35 psi, than the existing simulators by igniting a mixture of oxygen and acetylene to create the simulated blast. In order to accurately simulate the blast, the outlet of the simulator must be exhausted to the outdoors which will produce noise levels in excess of 140 dBA at five feet. The campus lies within 1800 feet of the nearest residential neighborhood and 950 feet of the nearest commercial neighborhood. The nearest outdoor occupied area on campus, a parking lot, is only 90 feet away. Sound pressure levels produced by the simulator as well as the exhaust requirements were evaluated in order to design a mitigation scheme to reduce noise to meet acceptable residential levels in the parking lot area. Phoenix Noise and Vibration worked with Vibro Acoustics to develop a silencer design to meet these criteria which will be reviewed in the presentation.
The Multi-Channel Maximum-Likelihood (MCML) method for infrasound detection and wave parameter estimation: Evaluation, implementation, and first applications
Authors: Le Pichon Alexis , Poste Benjamin , Vergoz Julien , Listowski Constantino , De Carlo Marine
Published: November 2022

The detection capability of the International Monitoring System (IMS) infrasound network is a key concern since ubiquitous coherent noise interfere with the identification of explosive events. The need to distinguish between incoherent wind noise and real coherent infrasonic wave signals has motivated the development of a new parametric stochastic model. We establish the expressions of both the Generalized Likelihood Ratio Test (GLRT) and the Maximum Likelihood Estimator (MLE). The major results are the expression of the asymptotic distribution of the GLRT under null hypothesis, leading to the p-value computation, and the expression of the asymptotic covariance. The Multi-Channel Maximum-Likelihood (MCML) detection is implemented in the time-frequency domain in order to discriminate between interfering signals. Extensive simulations with synthetic signals show that MCML outperforms the state-of-the-art multi-channel correlation detector algorithms in poor signal-to-noise ratio scenarios. We illustrate the performance of MCML on real IMS data, highlighting its capability to characterize the coherent ocean ambient infrasound noise in high resolution through comparisons with theoretical state-of-the-art numerical wave models as implemented at the LOPS research unit of IFREMER in the DATARMOR HPC center.
Infrasound generated by meteorological fronts as a background for infrasound monitoring of explosions
Authors: Chunchuzov Igor P. , Kulichkov Sergey , Popov Oleg , Perepelkin Vitaly
Published: November 2022

The results of study of temporal variations of the characteristics of infrasound (amplitudes, coherences, grazing angles, azimuths and horizontal phase speeds) detected during a passage of warm and cold fronts through the networks of microbarometers in the Moscow region are presented. .Infrasound radiated during periods of weather changes is an almost continuous background against which infrasound monitoring of explosions in the atmosphere is carried out. The significant differences observed in the characteristics of infrasound from warm and cold fronts are found. Such differences must be taken into account when detecting infrasound precursors of atmospheric storms. A possible aerodynamic mechanism for the generation of infrasound caused by the turbulent air flow around the geometric irregularities of the surface of meteorological front is proposed. [Work supported by RSF Grant No. 21-17-00021.]
Measurement of infrasound sensor self-noise
Authors: Gabrielson Thomas B. , Merchant B. J. , Rodrigues Dominique , Smith Chad M.
Published: November 2022

Self-noise is a critical performance characteristic of sensors intended for weak-signal detection and localization; however, the lower the self-noise, the more challenging the measurement. A recent international sensor-characterization exercise coordinated by the Provisional Technical Secretariat of the Comprehensive Nuclear-Test-Ban Treaty Organization included self-noise measurement of several infrasound sensors from 0.01 Hz to 10 Hz. Of three common methods for self-noise assessment—isolation of the sensor from external excitation, subtraction of common (coherent) components among several sensors, or de-activation of the sense mechanism—the first two were used in this exercise and the results highlight important measurement issues. In the infrasonic frequency range, isolation from external excitation is challenging. A sealed, thick-walled chamber attenuates ambient noise but heating from dissipation of power in the chamber interior can induce convection with large, low-frequency pressure fluctuations in the chamber. Capping the inlet(s) of a sensor creates a small, closed volume with strong coupling between temperature and pressure fluctuations. Subtraction of coherent components shared by co-located sensors can be effective in reducing the influence of ambient excitation; however, the process may be frustrated by errors in subtraction of large, nearly equal components or by unexpected electrical coupling.
Modeling of infrasonic and acoustic-gravity wave propagation, nonlinear evolution, and observable effects
Authors: Snively Jonathan B. , Calhoun Donna A. , Inchin Pavel A. , Sabatini Roberto , Heale Christopher J. , Zettergren Matthew D.
Published: November 2022

Mechanical disturbances associated with hazardous events—e.g., earthquakes, explosions (volcanic or man-made)—and severe weather – generate broad spectra of infrasound and acoustic-gravity waves (AGWs). These wave signals may provide diagnostic insight into the processes that generated them. They are routinely detected as fluctuations in atmospheric pressure, measured at ground or from balloon-borne platforms; at lower frequencies (<1 Hz), and where they may attain sufficient amplitudes at high altitudes, they may also be measured via the fluctuations that they impose in densities of layered species throughout the atmosphere and ionosphere. Thus, they provide complementary remote sensing opportunities, where waves and their effects, especially above and surrounding larger sources, may be diagnosed as they propagate. We review recent progress and techniques for high-fidelity modeling and simulation, to capture the propagation and evolution of low-frequency infrasound and AGWs throughout the atmosphere, from 0–500 km altitude (from surface to exobase). Strategies to (1) efficiently extend model simulation domains well into the diffusive thermosphere, to (2) connect models of atmospheric dynamics to those for other measurable processes (e.g., the ionosphere), and to (3) construct simulations that extend from source processes to specific remote sensing methodologies are discussed.
Homework problems inspired by one of humanity’s loudest achievements: The Saturn V
Authors: Gee Kent L. , Hart Grant W. , Anderson Mark C. , Mathews Logan T.
Published: November 2022

This paper discusses advanced undergraduate homework problems related to one of humanity’s greatest technological (and loudest) achievements—the Saturn V rocket. The homework problems are provided as supplementary material to a manuscript by the same authors, presently accepted to the Education in Acoustics Special Issue of The Journal of the Acoustical Society of America. Entitled “Saturn-V Sound Levels: A letter to the Redditor,” the article discusses how much of the information found online about Saturn-V acoustics is inaccurate and seeks to correct misconceptions and errors using available data and models. The supplementary homework problems increase pedagogical value of the article, which can be used as a teaching tool for concepts such as sound levels, power versus pressure, radiation efficiency, importance of decibel references, etc. In this presentation, an overview of the different homework problems will be given and specific problems solved with help from the audience.
Imaging three dimensional objects with ultrasound
Authors: Szabo Thomas L.
Published: November 2022

The ultrasound imaging laboratory provided students with the opportunity of determining what an unknown three dimensional object was from two-dimensional images. Armed with a portable diagnostic ultrasound imaging system, and internal calipers for quantification, students were given unknown objects from the creepy crawly collection. Each object was immersed in a small tub of opaque fluid. Students could adjust the imaging system to give different cross-sections or cut planes through the object. From this information and linear calipers, they were to determine what the object was and provide a quantitative three dimensional sketch. This experience gave them a taste of the chief difficulty in diagnostic imaging of the body: deciphering and recognizing tissue structures and organs from partial views. Other imaging exercises included the use of imaging phantoms to measure spatial and temporal resolution as a function of depth and other controls.
A potpourri of homework and test problems inspired by published research and/or classroom demonstrations
Authors: Russell Daniel A.
Published: November 2022

Fundamental engineering and physics topics in an acoustics course can be made more relevant and interesting when applied to problems involving real-world scenarios, both from technical apparatus and from the natural world. This presentation will highlight several “fun” homework and test problems inspired by reading acoustics journal papers or data collected during a classroom demonstration. For example: tree crickets cut holes in leaves to convert the ineffective sound radiation from a dipole source into a much more effective baffled monopole. Spiders locate prey on their webs by comparing arrival times between transverse and longitudinal waves in web fibers; a related problem can be modeled as a fixed-fixed string with a point-mass load (originally posed by Lord Rayleigh). A compound string presents a challenging boundary value problem, with theoretical results easily compared to animations and physical demonstrations and application to musical instruments. Deceptively “simple” demonstrations of standing waves in open pipes and Helmholtz resonators can be used to estimate damping losses and mass loading. Measured data from a tuning fork spectrum can lead students to evaluate appropriate boundary condition choices. Additional examples will be discussed as time allows.
Physical acoustics homework problems written by students: Undisciplined, irreverent, and original
Authors: Gokani Chirag , Haberman Michael R. , Hamilton Mark F.
Published: November 2022

“Study hard what interests you the most in the most undisciplined, irreverent and original manner possible” [Perfectly Reasonable Deviations from the Beaten Track, Richard P. Feynman, Basic Books, 2005]. Writing original homework problems is a powerful way students of physical acoustics can practice Feynman’s advice. Three problems that involve a broad range of concepts covered in introductory graduate-level physical acoustics courses illustrate how the student-author unleashed his creativity in an undisciplined manner, injected his problems with an irreverent sense of humor, and derived a great sense of originality and ownership over physical acoustics. The problems synthesize David T. Blackstock’s problems 1D-2, 1E-3, 1G-1, 1G-3, 7-6, 10-10, and 10-11 [Fundamentals of Physical Acoustics, David T. Blackstock, Wiley, 2000], addressing concepts including acoustic intensity, impedance, horns, enclosures, and radiation. [CAG was supported by the ARL:UT Chester M. McKinney Graduate Fellowship in Acoustics.]
Students are sitting in a room
Authors: Piacsek Andrew A.
Published: November 2022

Alvin Lucier’s seminal 1969 composition and recording, “I Am Sitting in a Room” provides a fascinating and engaging tool for students to improve their understanding of room acoustics, as well as their skills in analyzing spectral data. This meta-composition, in which Lucier’s description of the process plays an essential role, involves speech being recorded in a particular room, then repeatedly played back and re-recorded in the same room. Some frequencies in Lucier’s voice excite room modes; these are reinforced with each iteration, eventually to the exclusion of all other frequencies. This source material can be the basis for either a lab activity or a homework problem. For the latter, students are provided with high resolution spectrograms created by the instructor from two excerpts from Lucier’s 1981 recording (available online), one from an early iteration, and the other from a later one. Students are tasked with identifying the frequencies that correspond to room modes, then inferring the dimensions of the room used in the recording (“…different from the one you are in now.”) A variety of learning objectives at the undergraduate level, as well as challenges and successes from prior experience, will be discussed.
Complete and detailed inverse design for any arbitrary dispersion relations via non-local metamaterials
Authors: Kazemi Arash , Deshmukh Kshiteej , Liu Yunya , Deng Bolei , Fu Henry , Wang Pai
Published: November 2022

Phononic crystals and vibro-elastic metamaterials are characterized by their dispersion relations—how frequency depends on wave number/vector. While there are many existing methods to solve the forward problem of obtaining the dispersion relation from any arbitrarily given design. The inverse problem of obtaining a design for any arbitrarily given dispersion bands have only had very limited success so far. Here, we report a new design scheme capable of leading to arbitrary dispersion relations by incorporating non-local interactions between unit cells. Considering discrete models of one-dimensional mass-spring chain, we investigate the effects of both local (i.e., springs between the nearest neighbors) and non-local (i.e., springs between the next nearest neighbors and other longer range springs) interactions. First, we derive the general governing equations of non-local phononic chains. Next, we examine all design constraints for a linear, periodic, passive, statically stable, non-gyroscopic, and free-standing system. Finally, we perform analytical calculations and numerical simulations to solve the inverse problems. The results illuminate a new path toward novel wave manipulation functionalities, such as sophisticated combinations of roton-like, maxon-like, undulation-point and other zero-group-velocity (ZGV) modes, as well as multi-wavelength and multi-speed propagations of the same mode at the same frequency.