bluuebunny/crossref_metadata_2025 huggingface dataset:
Lumped parameter modeling of two dimensional mechanical and acoustical components
Authors: Childs Carter J. , Thompson Stephen C.
Published: November 2021

Multidomain lumped parameter models used to predict transducer performance are an efficient way of modeling full system responses. To increase the accuracy of such models, transmission lines can be used. Discretizing the line into small spatial segments allows for lumped parameters to be used for modeling partial differential equations. Segmentation in onedimension has long been used in circuit simulators and multidomain analysis codes. This work presents a solution in two dimensions for both mechanical and acoustical physical domains. For example, the analysis of the mechanical motion of membranes and the acoustical behavior of thin cavities can be analyzed. This enables increased accuracy in modeling a transducer as the shape function of the membrane is accounted for. Further, the mechanical and acoustical physics can be coupled for an appropriate Multiphysics interaction. This is a simple demonstration of the possibilities that could be achieved using a spatially discretized multidomain models for more complex transducers.
Towards aeroacoustic measurements under hyperbaric condition
Authors: Kandias Constantinos S. , Morgan Nick , Shields Andrew , Greenwood Eric , Miller Mark
Published: November 2021

Full scale experimental aeroacoustic measurements are often impractical due to the prohibitively high costs associated with full scale models and large facilities capable of far-field acoustic measurements. Although small scale models can provide useful acoustic data, this scaling is limited by the inability to achieve full scale equivalent aerodynamic conditions at smaller scale. However, aerodynamic similarity can theoretically be achieved using much smaller models under hyperbaric conditions. While promising, microphones and anechoic materials used in acoustic experimentation are not explicitly designed for use in such conditions, and so their behavior must be verified. To characterize the response of condenser microphones at elevated pressures, a pistonphone style calibrator was developed to operate over a range of pressures. Likewise, for the anechoic materials, an impedance tube was developed to evaluate their performance at elevated pressures. The performance of these systems under atmospheric pressure and hyperbaric conditions is discussed, along with details of the experimental method, and observed microphone response, and acoustic insulation performance at high pressure.
Aluminum nitride piezoelectric micromachined ultrasound transducers with applications in sonic anemometry
Authors: Steve Freidlay , Littrell Robert , Core Craig , Banfield Don , White Robert D.
Published: November 2021

Recent results demonstrate the promise of sonic anemometry for accurate, three dimensional, high update relative wind measurements in high altitude (stratospheric) balloons and for planetary science missions on Mars, Venus, and other environments (Banfield, JASA 2016, White, ASA 2020, White, AIAA 2020). For these applications, low weight and small size is desirable. We propose an aluminum nitride piezoelectric micromachined ultrasound transducer (PMUT) as a candidate for a small (∼1 cm3) low weight (∼10 g) sonic anemometry system. Two PMUT designs were fabricated using Vesper Technologies MEMS microphone process by Vanguard Semiconductor International on 1.4 × 1.4 mm2 die. The first device has 270 μm diameter diaphragms and operates at 610 kHz, the second 190 μm diameter diaphragms and operates at 890 kHz. By operating at these high frequencies, the acoustic path length can notionally be reduced to 1 cm, while still retaining sufficient phase resolution to measure wind with 1 to 10 cm/s accuracy. The substantial challenge is producing sufficient signal to overcome acoustic absorption at these elevated frequencies. This design is aggressively exploratory in nature. The PMUT devices have been fabricated and operate, but the sonic anemometry system has not yet been demonstrated. [Work supported by NASA PICASSO NNX16AJ24G, NSF 1934553 and NSF 2110083.]
Abstract synthesis representation of nonlinear behaviour in coupled resonators
Authors: Smyth Tamara
Published: November 2021

In this work, abstract synthesis techniques known as frequency/amplitude/phase modulation (FM, PM, and AM, respectively) are explored in musical acoustic systems involving coupled oscillators, nonlinear mechanical resonators and feedback. Though these systems are frequently modeled having acoustic/physical parameters (and units), there is a strong musical benefit of an abstract representation in which input parameters control more perceptual aspects of the produced sound. Previously coined “loopback FM" is an extension of the well known FM synthesis technique in which a carrier oscillator “loops back" to modulate its own frequency, resulting in behaviour that is characteristic of nonlinearities. With reference to loopback FM, along with its strongly related feedback PM/AM, nonlinearities that influence sounding frequency, spectral bandwidth and amplitude envelope are explored with musical instrument examples.
An analysis of angular directivity for small caliber firearm noise
Authors: Campbell Steven C. , Wall Alan T. , Murphy William J. , Rasband Reese D. , Gee Kent L.
Published: November 2021

Accurately describing the sound field generated by an impulsive source is non-trivial. Conventional methods for analyzing impulsive noise of firearms consists of deploying one or more circular microphone arrays centered on the muzzle of the source. Currently, much debate exists around the design of these microphone arrays (radius, quantity of sensors, angular spacing, etc.) and the resulting effect on capturing source directivity of the impulse event. An in-depth investigation of data collected on small caliber firearms operating in outdoor environments is performed with an emphasis on describing source directivity as a function of (1) array radius, (2) quantity of microphones, and (3) angular spacing. Ultimately, given a sufficient circular microphone array, the angular directivity of an impulsive source can be generalized using analytical curve fitting functions.
Applications of building information modeling software to HVAC noise prediction
Authors: Underwood Samuel H. , Wang Lily M.
Published: November 2021

This paper presents a methodology and workflow for utilizing Building Information Modeling (BIM) software to expedite the calculation of duct borne noise according to Chapter 49 of the ASHRAE Handbook – HVAC Applications. Using Dynamo script for Autodesk Revit, relevant building mechanical system parameters are extracted to perform noise calculations with reduced manual input. Resulting predictions for receiver sound pressure levels are compared to other software tools available in the industry. Advantages and limitations of this approach are weighed to assess the utility of Building Information Models in the context of the noise prediction workflow. The results of this effort support the development of more robust duct noise prediction tools that are not only more accurate but also more user-friendly.
Integrated heating, ventilation, and air conditioning noise control solutions
Authors: Dziedzic Chris
Published: November 2021

There are a wide variety of acoustical considerations with respect to commercial building heating, ventilation and air conditioning (HVAC) systems. This presentation will review and discuss integrated solutions and noise control products that can be utilized to solve noise problems during the design process. Air Moving and Air Distribution devices can affect the overall acoustics of a space and when selected properly, help to reduce the background sound with the space. There are also a wide variety of noise control products available to help mitigate and attenuate sound transmission and transfer from the noise source to the receiver within commercial buildings. This presentation will review some of the most commonly used noise control products and their overall design characteristics to provide understanding on how they operate.
Paint a clearer picture with in situ auralizations
Authors: Kanter Shane J. , Springthorpe Chris , Dulworth Nicolaus T. , Glosemeyer Petrone Robin , Pfeiffer Scott
Published: November 2021

Communication is at the heart of everything we do as consultants. We are constantly striving for new and better ways to guide our clients to make informed decisions. In situ auralizations of major pieces of future mechanical / electrical equipment allows major stakeholders and decision makers to get an aural sense for various equipment configurations, enclosure types, and barrier wall buildups prior to installation. After the auralization, board members and homeowners from past projects had a richer understanding of the anticipated experience at the property line and nearby classroom spaces when compared to reviewing graphs and charts alone. We will explore the value of, and challenges with, this in situ auralization method, as well as some future improvements to further validate the process through the lens of two past projects—New Trier High School and Lake Bluff Middle School in Illinois.
Update on using metal domes for wind noise reduction at infrasonic frequencies
Authors: Talmadge Carrick
Published: November 2021

The utility of infrasound for long range monitoring applications such as remote chemical explosions, or natural sources of infrasound such as tornadoes, volcanoes or hurricanes, continues to be hampered by the high noise floors experienced in the presence of high winds. Wind noise is typically filtered using pipe arrays. But these generate significant distortion, making them non-ideal for signals with significant frequency content above a few Hz, and do not produce sufficient noise reduction during windy measurements even at their optimal frequency band (0.5–1 Hz), making their utility generally limited to low-wind-noise periods. We present here an update on resesarch performed by the National Center for Physical Acoustics (NCPA) using field sites near Oxford (University of Mississippi Field Staiton) and at the Sandia National Laboratory Facility for Acceptance, Calibration, and Testing (FACT) site. The 20-foot dome at the FACT site is collocated with an IMS 18-m rosette filter and a wind noise filter developed by the University of Alaska Fairbanks. We compare in this presentation the relative performance of traditional pipe arrays to the 20-ft dome. The performance of smaller wind domes, including 42-in.2 perferorated metal domes developed at the NCPA, are also discussed.
Keep it simple: A right conical infrasound windscreen from off-the-shelf components
Authors: Alberts W. C. K.
Published: November 2021

Windscreens for higher frequency infrasound are a continued topic of discussion because the ideal has yet to be found, i.e., an inexpensive, easily shipped, compact windscreen with a flat 3 Hz to >20 Hz passband and nearly zero transmission loss. Recent research has shown that the robust porous hose, porous fabrics, and perforated metal domes are capable of filling many of those needs. However, each technology has drawbacks that necessitate further research to arrive at a greater understanding of the windscreen and to approach the ideal. Guided by this previous infrasound windscreen research, a right conical windscreen was constructed from easily obtained commercial products and subsequently tested beside previously characterized windscreens. The presentation will discuss results of the experimental program to include comparisons of power spectral densities and transfer functions.
Application of spectral-based wind noise reduction method to acoustical measurements
Authors: Cook Mylan R. , Gee Kent L. , Transtrum Mark K. , Lympany Shane V. , Calton Matt
Published: November 2021

Wind-induced microphone self-noise is a non-acoustic signal that may contaminate outdoor acoustical measurements, particularly at low frequencies, even when using a windscreen. A recently developed method [Cook etal., JASA Express Lett. 1, 063602 (2021)] uses the characteristic spectral slope of wind noise in the inertial subrange for screened microphones to automatically classify and reduce wind noise in acoustical measurements in the lower to middling frequency range of human hearing. To explore its uses and limitations, this method is applied to multiple acoustical measurements collected in both urban and rural environments. The method can be applied to one-third octave band spectral data with different frequency ranges and sampling intervals. By removing the shorter timescale data at frequencies where wind noise dominates the signal, the longer timescale acoustical environment can be more accurately represented. While considerations should be made about the specific applicability of the method to particular datasets, the wind reduction method allows for simple classification and reduction of wind-noise-contaminated data in large, diverse datasets. [Work supported by U.S. Army SBIR.]
Bats use predictive strategies to track moving auditory objects
Authors: Salles Angeles , Diebold Clarice , Moss Cynthia F.
Published: November 2021

Big brown bats rely on acoustic information from the echoes of their own vocalizations to hunt insects in flight. Unlike many predators that use vision as their primary sensory system, bats compute the 3D position of insect prey from discrete echo snapshots, which yield interrupted sensory information about the target trajectory. Furthermore, this information may be further diminished by clutter in the environment and erratic flight maneuvers of prey. The question arises about the strategies employed by bats to successfully track and intercept their prey. We devised an ethologically inspired behavioral paradigm to directly test the hypothesis that echolocating bats build internal prediction models from dynamic acoustic information to anticipate the future location of moving auditory targets. Collectively, our results demonstrate that the echolocating big brown bat integrates acoustic snapshots over time to build prediction models of a moving auditory target’s trajectory and enables prey capture under conditions of uncertainty. Furthermore, we build on past work to propose a new model that describes bat flight trajectories of bats employing predictive strategies.
Investigation of geometrical factors effects on sound silencing behavior of mass attached membrane-type acoustic metamaterials
Authors: Aghamiri Mohammad , Ghaffarivardavagh Reza , Mahjoob Mohammad J.
Published: November 2021

Membrane-type acoustic metamaterials have drawn significant attention in recent years due to their capacity in generating low frequency band gaps. To date, numerous analytical and numerical approaches have been developed to study and evaluate acoustic performance of this type of metamaterials toward improving their sound silencing behavior. In this paper, we have used point-wise matching method to study different geometrical factors of mass attached membrane and investigate how these factors contribute to the sound silencing behavior. Additionally, the full-wave simulation of these exotic mass-attached membranes are carried out to numerically validate the results. The paper herein, provides an insight on how tuning the geometrical parameter of mass-attached membrane yields broadening the silencing bandwidth. Developing wide-band membrane-type metamaterial pave the way for the emergence of myriad applications ranging from noise mitigation to acoustic energy harvesting.
Reproducibility and repeatibility: Why acoustics consultants, manufacturers, and academics should care
Authors: Way Evelyn
Published: November 2021

Trust in acoustic data from all sources is very low. The resulting crisis of confidence in end users, architects, contractors, and designers leads to overly conservative design standards or a sense that “nothing matters so why bother doing anything" that might improve the acoustic performance. While this is partly because buildings are complex systems with many interrelated variables affecting the results, part of it is due to normal measurement variation. Study of measurement uncertainty and experimental design began in the late nineteenth and early twentieth centuries, and the fruits of statistical analysis can be found in the repeatability and reproducibility measurements that populate the ASTM standard Precision and Bias statements. Repeatibility and reproducibility can be used for three purposes: 1. to evaluate the quality of the standard, 2. to adjudicate when two testers’ measurements disagree, and 3. to evaluate edge cases for compliance with specified values. Unfortunately, the reproducibility and repeatability data in the E33 Building and Environmental Acoustics standards are not typically statistically rigorous enough to provide useful information. By supporting and participating in round robins and interlaboratory studies, the uncertainty in our measurements can be quantified, and we as a community can be confident in our measurement data.
Improvements to the standards for the testing of noise protection equipment
Authors: Sauro Ronald
Published: November 2021

This paper will suggest improvements to the applicable testing standards for the testing of hearing protection units. The units can be over the ear or in the ear units. These suggestions will make the tests more objective and less about using people as test objects. We will discuss when sound is hazardous and what time has to do with the level of danger. We will discuss passive attenuation and active attenuation as well as amplification applications to aid in communications between users of such devices.
Beyond reverberation time: Toward a new geometric approach to room acoustics
Authors: Belanger Zackery
Published: November 2021

The limitations of the most prevalent parameter in room acoustics—reverberation time—are numerous, and some arise from absorption coefficients measured in reverberation chambers and, more broadly, assumptions of a diffuse field. The result is that material performance metrics and reverberation time prediction—whether calculated or simulated—are reliable over a more limited range of room types than is often recognized in practice. In this work, a new approach that could widen this range is presented via a potential new geometric view of room design. Room geometry has the potential to seamlessly connect dry, diffuse, reverberant, and focusing spaces (e.g., domes, cylinders) into one range of continuous design possibility. Evidence for the efficacy of this approach will be provided via a scrutinization of the behavior of reverberation time equations, including Sabine's, and empirically via room measurements of a space with and without diffusive boundaries: Studio 2 at the Experimental Media and Performing Arts Center in Troy, NY. Insight will also be lent into strange laboratory results, such as variations in measured absorption coefficients based on splitting and spreading of test samples.
Advances in impact noise insulation testing
Authors: Dong Wayland , Lo Verde John , Rawlings Samantha
Published: November 2021

Recent years have seen numerous changes and proposed changes to the measurement and ratings of impact noise insulation testing. New ASTM ratings have been published this year for evaluating low-frequency (E3207) and high-frequency (E3222) impact noise, based on the authors’ research [J. Acoust. Soc. Am. 141, 428-440 (2017)]. This paper will review on-going research in several areas of impact insulation testing, including a modified laboratory method for simultaneously testing multiple floor toppings. The authors have previously published that the existing Impact Insulation Class (IIC per E989) rating be modified to remove the rule limiting the deficiency in any third-octave band to 8 dB [“Reconsidering the 8 dB Rule in ASTM Impact and Airborne Ratings”, Noise-Con 2020]. This 8 dB rule has origins in concerns about transmission loss, and most of the analysis on the issue historically has in terms of airborne noise insulation, but the authors show that the consequences for impact testing are more severe. The statistical effects of the rule are also discussed along with the effects on the design of floor-ceiling assemblies. Finally, the statistical uncertainty of laboratory impact testing continues to be a subject of investigation, and recent results and reviewed. The authors discuss the need to continue to advance testing technology to provide reliable and quality information to those who evaluate, engineer and predict impact noise.
Comparison between sound insulation parameters obtained through interrupted noise method standard 16283 and new method from standard 18233 from international organization for standardization
Authors: Belletti Romero Tiago , Carlos Giner José
Published: November 2021

The grow of the population density is a reality present in large urban centers. Linked to this, the valorization of the square meter is a common process that leads to the verticalization of buildings and the tendency to smaller dwellings. Such trends are more susceptible to problems related to noise transmission. Therefore, it is essential that some criteria are established to provide a minimal sound insulation between residences. As well as reliable and standardized methods of measuring such parameters for a correct assessment. Thus, this work compares two methods of measuring the acoustic insulation of building systems in loco. Measurements from the interrupted noise method according to ISO 16283 will be compared with measurements obtained with the new method described by ISO 18233: 2006, which first obtains the impulsive response of the system to then obtain sound pressure levels and decay rates. Not only will they be compared for the results obtained, but also for the time taken for the measurements, ease of use and transport of the equipments. Some comparisons with simulated values will also be made using the Sonarchitect software.
A proposal for a new 1/3 octave band noise criteria
Authors: Struck Christopher J.
Published: November 2021

A proposal for a new noise criteria (NC) method in 1/3 octave bands to supersede the legacy ASA/ANSI S12.2-2019 octave band metric is presented. 1/3 octave band NC curves from NC 65 to NC 5 are derived from the existing octave band curves, adjusted for bandwidth, fit to continuous functions, and redistributed progressively over this space. The proposed 1/3 octave band NC 0 contour is based upon the diffuse field hearing threshold at low frequencies and parallels the existing NC curves at high frequencies. This synthesis is described in detail. NC values are calculated using both the proposed and legacy methods for a number of different room noise spectra. The resulting values were found to be similar for both methods. NC ratings using the proposed method are particularly applicable to very low noise level critical listening environments such as recording studios, scoring stages, and cinema screening rooms, but are shown to also be applicable to higher noise level environments. The proposed method better tracks audibility of noise at low levels as well as the audibility of tonal noise components, while the legacy method as originally conceived generally emphasizes speech interference.
Modeling a representative room to evaluate sound power measurement methods for ASTM ISR testing
Authors: Girdhar Sunit , Barnard Andrew R. , Lo Verde John , Dong Wayland
Published: November 2021

ASTM ISR (Impact Sound Rating) test method suffers from non-reproducibility problems, especially in lower frequency bands in smaller rooms where the sound field is non-diffuse. The problem arises from the fact that Sound Pressure Level is measured in these rooms, which is dependent on the room dimensions if the sound field is non-diffuse due to low modal density. Currently, this non-diffusivity is ignored. We propose to measure sound power radiated from the ceiling instead of volume-averaged sound pressure level, which is independent of room dimensions regardless of the type of sound field in the receiving room. This study evaluates sixteen different ideas to measure sound power levels in the receiving rooms through a simulation model of a representative room using Simcenter 3D. Each method's pros and cons in the simulation are used to downselect methods to test in the field.
Experimental investigation of parametric array for low frequency measurement system
Authors: Jung Donghwan , Song Jiyoung , Kim J. S. , Lee Jaehyuk
Published: November 2021

To evaluate the performance of an equipment or object in underwater acoustics, the acoustic properties of acoustic materials should be accurately predicted and measured. The measurement of acoustic properties via panel testing in water tank require a narrow beam due to unwanted signals such as reflection from walls and diffraction signal. However, in the case of low frequency sound source, it generally has broad beam, and in order to have narrow beam, it is difficult to operation and physical limitation. These limitations and problems can be overcome by using a small size of parametric array capable of generating high-directional low-frequency signals. In order to use the parametric array as a sound source for an acoustic measurement system, it is necessary to understand the characteristics of the parametric array in near field. So this study was performed an experimental investigation on parametric arrays and study to construct an optimal system. Numerous factors such as the effect of pseudo sounds and the optimal distance between the source and receiver were considered to construct the system, and the results of experimental investigations, such as an efficient method to remove the effects of pseudo sounds and effective length, were confirmed.
Acoustical holography-based sound power decomposition of a highly heated, large eddy-simulated supersonic jet
Authors: Gee Kent L. , Leete Kevin M. , Liu Junhui , Wall Alan T.
Published: November 2021

In recent years, large-eddy simulation (LES) has proved a powerful tool for modeling increasingly heated, supersonic jets and analyzing their source characteristics. This paper describes an investigation of the acoustic source characteristics from an LES of an underexpanded jet with total temperature ratio of seven. Using frequency-domain pressures and particle velocities at, and generated from, the Ffowcs Williams Hawkings surface (FWHS), holography and intensity techniques are used to perform an axial decomposition of radiated sound power from the jet, whereas a far-field arc produces a narrow, nonphysical source distribution, the intensity from the near-field array and FWHS surface yield sound power decompositions that approximate the nozzle lipline squared-pressure’s spatial distribution. For this LES, the peak sound power is radiated just upstream of the potential core tip, and over 90% of power is radiated upstream of the supersonic core tip.
Atmospheric sound transmission loss uncertainties induced by sea roughness
Authors: Vecchiotti Andrea , Ryan Teresa J. , Cobb Faith A. , Vignola Joseph , Turo Diego
Published: November 2021

This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different sea states. Water roughness is pseudo-randomly generated using an ocean wave spectrum. The GTPE predictions are compared with those obtained using the Crank-Nicholson parabolic equation (CNPE) solver. When using the CNPE the sea surface is flat and has a surface impedance equivalent to that of a rough surface. The use of the GTPE is less computationally efficient but provides insight on the detectability of an acoustic source at sea. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 500 m from the source. These relationships are presented for typical diurnal and nocturnal thermal gradients and for different elevations from the water surface.
A mixed Fourier transform for impedance boundary conditions of acoustic waves at grazing incidence
Authors: Carr Alexander N. , Lonzaga Joel B. , Miller Steven A.
Published: November 2021

Acoustic propagation in the atmosphere near the Earth’s surface at grazing incidence is influenced by ground impedance. Consequently, numerical simulations must use an impedance ground boundary condition in order to accurately predict ground effects associated with grazing incidence. A mixed Fourier transform method for impedance boundary conditions has been developed for parabolic approaches by the electromagnetics community. Here, the mixed Fourier transform method is adapted and validated for acoustic wave propagation. The one-way solution of the Helmholtz equation is computed with a modified angular spectrum approach to account for a locally reacting surface using a mixed Fourier transform in the vertical direction. Numerical simulations are presented that focus on sonic boom propagation near the ground in the shadow zone. The simulations demonstrate the utility of the mixed Fourier transform method to account for ground impedance effects that are ignored by ray theory-based propagation codes. Consequently, the method extends sonic boom prediction to the lateral cutoff and shadow zone regions. [This research is supported by the Commercial Supersonic Technology Project of the National Aeronautics and Space Administration under Grant No. 80NSSC19K1685.]
Introduction to the Computational Acoustics Technical Specialty Group
Authors: Wilson D. Keith
Published: November 2021

In acoustics, as in other fields, computation makes a seemingly ever-growing contribution to scientific and engineering progress. The Computational Acoustics Technical Specialty Group (CA TSG), which first met officially at the Fall 2018 ASA meeting, provides a forum for computational acoustics research that had often been discussed independently within many of the TCs. The CA TSG thus facilitates exchanges of recent advances and experiences with computational methods having broad applications across acoustics. Topics considered by the CA TSG include: (1) numerical methods for wave propagation, scattering, structural interactions; (2) optimization, parallelization, and acceleration of computational algorithms; (3) validation, benchmarking, and uncertainty analysis; (4) computational learning methods; (5) data analytics and visualization; and (6) practical utilization of acoustical computations for engineering and noise control.
An introduction to Technical Committee on Underwater Acoustics
Authors: Yang Jie , Reeder D. Benjamin
Published: November 2021

The Acoustical Society of America Technical Committee on Underwater Acoustics investigates sound propagation in underwater environments such as oceans, lakes, rivers and tanks. Sound waves can travel thousands of kilometers in water and therefore, have been widely used as an effective tool to study the ocean for both economic and defense purposes. It is an interdisciplinary, observation-driven field of study that involves physics, oceanography, marine biology, engineering, and signal processing. In this talk, several representative research areas are presented, including measurement and modeling of sound propagation and reverberation, and ocean ambient sound field monitoring and characterization. A number of large, integrated field experiments are also presented, to illustrate the manner in which observations are designed to pursue scientific questions.
Selected research in physical, structural, and underwater acoustics at WSU associated with Logan Hargrove’s ONR scientific program
Authors: Marston Philip L.
Published: November 2021

Logan Hargrove, during his service as an ONR scientific and program officer, facilitated basic research at Washington State University for two decades. The Hargrove era investigations included research into: acoustic scattering physics and holographic imaging for elastic objects in water, high-order caustic wave-fields, generation and holographic-verification of acoustic vortex beams, light scattering by bubbles and drops, acoustical and optical radiation forces, nonlinear wave interactions in heterogeneous media, and cavitation induced by shock-wave reflection. The scattering research progressed from symmetric objects to objects of greater complexity. While the bulk of the funds provided went to support graduate researchers, some laboratory improvements of lasting value were also facilitated through the ONR support. The impact of that support on ONR’s research interests and on the development of careers of several students who went on to make long term contributions to those interests will be summarized. While the emphasis is on the aforementioned two decades, some subsequent developments dependent on the facility improvements are also noteworthy. Recollections of some personal encouragement provided by Logan prior to receiving ONR support will also be noted. [Research supported by the Office of Naval Research.]
The role of Logan Hargrove in the creation of the National Center for Physical Acoustics
Authors: Crum Lawrence A.
Published: November 2021

Shortly after I arrived at the University of Mississippi (UM), Hank Bass proposed that any member of the Ole Miss faculty with an interest in acoustics join the Physical Acoustic Research Group at the University of Mississippi (PARGUM), and, informally constituted, we all agreed to devote 10% of our time to the promotion of this entity. One of the first items of business was to increase our available laboratory space. On one of Logan’s visits, Logan agreed to speak to the Chancellor and said that, within his power, he would continue to provide ONR support for PARGUM. This meeting with the Chancellor was instrumental in the assignment of the Ole Band Building to PARGUM, but more importantly, the Chancellor became supportive of Hank’s initiative to seek the engagement of Mississippi’s powerful congressional delegation in creating a national center for acoustics. With the enthusiastic support of the Chancellor, NCPA was created by an Act of Congress in 1986.
Echolocating bats modify biosonar emissions when avoiding obstacles during difficult navigation tasks
Authors: Simmons Andrea M. , Thorson Charlotte R. , McLaughlin Madeline , Polanco Pedro , Tuninetti Amaro , Simmons James A.
Published: November 2021

Big brown bats modulate their biosonar emissions in both time and frequency when flying through acoustically cluttered environments. We challenged single bats or bats in pairs to fly along a narrow U-shaped corridor 7 m in path length formed by rows of vertical plastic chains, while also avoiding additional interspersed horizontal chains. Bats emitted calls in complex sonar sound groups in all flight conditions. When no added horizontal obstacles were present, each bat’s flight success rates averaged 80%; introducing horizontal obstacles decreased success rates to 45-65%, with little improvement over several days. When two bats flew simultaneously from opposite ends of the U-shaped path, they rarely collided, instead swerving closely past or keeping farther apart in elevation. They increased call rate and call amplitude, while decreasing terminal FM broadcast frequency, as they approached near the middle of the U-shaped path. Increases in call amplitude persisted throughout the remainder of the flight while call rate and terminal frequency returned to baseline levels. These data show the limits of call modifications during difficult maneuvers in dynamic conditions. They demonstrate the bat’s effective awareness not only of the continuously distributed clutter but also of another, moving bat. [Work supported by ONR.]
Comparison of discrete and continuous auditory detection for real and simulated over-flight signals
Authors: Mobley Frank S. , Thompson Eric R. , Ugolini Margaret H. , Fox Elizabeth L. , Gallagher Hilary
Published: November 2021

Many auditory detection tasks employ discrete stimulus samples, presented during well-defined, brief observation intervals at predictable times. However, real-world listening is a continuous process without clearly defined intervals possessing indicators of when to listen and respond. The current study was designed to investigate the differences between a discrete, interval-based method and a continuous, free-response method. Increasing understanding of differences in methodology leads to a model predicting real-world perception from interval-based laboratory detection data. Real and simulated aircraft over-flight signals were presented to human subjects in a continuous, free-response task in which the subjects indicated when they could detect the signal. The same signals were also divided into 1-s audio files, which were presented to the same subjects in different sequences using a single-interval, forced-choice paradigm. The results indicated that the presentation sequence does not have an effect on human performance. Comparison of psychometric function derived from interval-based and free-response data indicated a shift to higher signal-to-noise ratios on approach when no clear response interval is provided, but the same shift was not observed on departure.
The quantification of head-related transfer function’s dependency on anthropometric features
Authors: Kailas Ganesh , Kumar Voona Satish , Tiwari Nachiketa
Published: November 2021

The work quantifies the anthropometric dependency of the head-related transfer functions(HRTFs). The human body modifies the soundwaves while traveling to the ear canal from different spatial locations, and the HRTF defines the transformation. The peaks and notches in the HRTF magnitude spectrum, generated by the complex asymmetrical shape of the outer ear (pinna), are essential for sound localization in the elevation plane. However, the anthropometric dependency of HRTF is not well quantified in the literature. The huge experimental cost of conventional HRTF measurement methods is a hurdle in these studies. To overcome this, distance-dependent HRTFs have been evaluated using the finite element-based computational tool on surface meshes of the human upper body with different pinnae. The size and interaural position of the pinna were altered, and various HRTF simulations were carried out in the study. The frequency shift of the spectral peaks and notches in the magnitude spectrum was examined to understand its anthropometric dependency. The dependency of HRTF on human anthropometric features was appraised in the proposed work. It can be beneficial in predicting personalized HRTF according to the size and interaural position of the subject’s pinna.
Differentiating perceptual, procedural, and task learning for an auditory temporal discrimination task
Authors: Zhen Leslie , Pratt Sheila
Published: November 2021

Perceptual or stimulus learning (PL) reflects experience-driven improvements in the ability to detect changes in stimulus characteristics. The time course for PL overlaps with that for procedural learning (acquiring general skills and strategies) and task learning (learning the perceptual judgment specific to the task), making it difficult to isolate their individual effects. This study was conducted to examine the impact of exposure to stimulus, procedure, and task information on learning for auditory temporal-interval discrimination. Eighty-three listeners completed multiple sessions requiring auditory temporal-interval discrimination (target learning task), but before these sessions listeners were exposed to one of three conditions that differed by the information conveyed about the target task’s stimulus, procedure, or task characteristics. Significant learning occurred but an exposure effect was not found when examined across sessions. However, percentage improvement scores (initial to final) revealed that listeners exposed to elements of the target task demonstrated larger percentage improvements on that task compared to naïve listeners without any prior experience in a manner that suggested that stimulus and procedural learning were possible drivers of temporal learning. These findings could clarify the influence of experience on temporal PL and inform future research aimed at developing training paradigms that optimize perceptual improvements.
Detection of aircraft targets varies as a function of target and masker temporal complexity, similarity, and realism
Authors: Ugolini Margaret H. , Mobley Frank S. , Thompson Eric R.
Published: November 2021

The complexity of real-world auditory scenes makes it difficult to disentangle the factors that drive detectability of sounds within those scenes. However, many real-world applications of auditory perception research require the disentanglement of these factors – for example, to predict the effects of aircraft noise on the public depending on the ambient sound environment and the aircraft itself. The present study investigates effects of masker temporal complexity and similarity to targets on the detectability of helicopter target sounds. We investigate three levels of masker temporal complexity – urban sound scenes (high); synthetic versions of each scene that preserve overall statistics (medium); and noise of the same spectrum as the real scene (low). Target similarity was probed in a way that would occur in the world—as a function of the presence of other engine sounds. Each real masking sound could be comprised of only engine noise, engine sounds embedded in an urban scene, or a scene without engines. This provides maskers with three levels of target similarity. Combination with the three levels of temporal complexity allows us to probe interactions between temporal complexity and engine-related signal energy. Effects of target signal characteristics and interactions with signal to noise ratio will be discussed.
Feature dependence of neural mechanisms for divided auditory attention
Authors: Howerton Kayla , Deng Yuqi , Shinn-Cunningham Barbara , Choi Inyong
Published: November 2021

Multi-talker social situations require the listener to focus attention on a single talker, as well as monitor and divide attention to additional talkers, as needed. The neural mechanisms behind how one can efficiently divide their attention has yet to be thoroughly explored. The current study investigates these neural mechanisms via electroencephalography when participants listen to competing speech and focus or divide attention. Participants were tasked either to focus and maintain attention on an initial target or to divide attention, listening to the initial target but monitoring for a potential, later “supertarget.” At the end of each trial, listeners recorded the target stimulus, defined either by location or talker identity (male or female), via a keypad. A pilot study found that focused, location-based attention modulates alpha oscillations in parietal cortex, thought to reflect inhibition of non-target locations. Here, we test the hypothesis that, during talker identity trials, attention enhances the neural representation of the target via talker identity features through enhanced beta oscillations in the frontal and middle temporal gyrus. Comparison of electroencephalography between divided and focused attention conditions suggests that using different acoustic features to focus or divide attention recruits completely different neural mechanisms.
Thin Helmholtz resonators for a broadband acoustic metamaterial
Authors: Rajendran Vidhya , Méndez Echenagucia Tomás I. , Piacsek Andrew A.
Published: November 2021

Acoustic absorption of the low to mid-frequency range of human speech (80 to 800 Hz) is important for open office environments and can be achieved with resonant absorbers. However, traditional Helmholtz Resonators (HRs) are not an efficient solution because of the large dimensions required and their limited acoustic performance. A heterogeneous array of novel HRs geometries that are compact and tuned to different frequencies function as a metamaterial that provides broadband absorption. A numerical study of the acoustic absorption of different resonator shapes is carried out to optimize performance in the target frequency. These geometries are compared based on their absorption coefficients, resonator dimensions, and theirmass-productibility. The acoustic behavior of the HRs is modeled in COMSOL Multiphysics using the Finite Element Method and the efficient geometries were selected for designing the broadband acoustic metamaterials. The accuracy of the numerical model is tested experimentally in an impedance tube, using 20 cm × 20 cm panels fabricated with embedded resonator arrays.
Multiplexed acoustic holography using an iterative angular spectrum approach
Authors: Meighan Ian , De Asis Edward , Shen Chen
Published: November 2021

Technological advancements have enhanced the capability of acoustic holography over the years. A major drawback for current techniques is the lack of ability of multiplexing, which has limited their potentials in ultrasound imaging and acoustofluidics. In this work, we propose an algorithm based on an iterative angular spectrum approach to overcome this limit. An optimized phase distribution at the source plane can be obtained which can project multiple acoustic projections at various distances and frequencies. As such, the acoustic fields at the image planes are encoded onto the same source plane and this facilitates the design of 3D printed acoustic kinoforms integrated on a single element transducer. The parameters including the frequency and projection distance to obtain the best performance are tested. The algorithm can be used in conjunction with other optimization strategies to fine tune pressure fields and further improve the image quality. The results are expected to be useful in medical ultrasound and acoustofluidics where complex acoustic field projection is needed.
Acoustic black hole duct with damping material
Authors: Petrover Kayla
Published: November 2021

Acoustic black holes have a tapering thickness profile to create the idealized phenomenon of zero reflection and transmission. The phenomenon entails wave propagation in an ideal medium where the profile tapers according to the power law shortening the wavelength and decreasing the wave speed. Consequently, the wave’s travel time tends to infinity so that the wave never reaches the end of the acoustic black hole and cannot be reflected or transmitted. For the application of a duct, thin annular rings of inner radii decrease with the power law to control pressure levels. An infinite number of rings and a final cross sectional area of zero is needed to create the ideal case and is impossible to manufacture. A common method to compensate for imperfections is to use damping material, such as in the experiment [El-Ouahabi et al, in International Conference InterNoise 2015 (2015)], though their results did not show that adding damping to the termination made an improvement. This work aims to find which areas of the acoustic black hole duct are most beneficial to add damping to in order to reduce the reflection and transmission coefficients by measuring the properties of different damping configurations. [Approved for Public Release Distribution Statement A.]
Isolation of flexural waves in a wide and low frequency range using a phononic beam with acoustic black hole configuration
Authors: Park Seongmin , Jeon Wonju
Published: November 2021

We propose a phononic beam to realize flexural wave bandgaps in wide and low frequency regimes. A unit cell of the phononic beam consists of two uniform parts and a tapered part with acoustic black hole configuration sandwiched between uniform parts. We identify the effects of geometrical parameters of the ABH-based phononic beam on band structures and determine those geometrical parameters to obtain a bandgap from 3.6 Hz to 237.9 Hz with a lattice constant of 1/33 wavelength. For experimental realization, the displacement transmission of the phononic beam is measured by impact hammer test, and the result shows that low transmission of –35 dB to i–10 dB could be achieved in the wide bandgap.