bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of audio signals from elevated harmonic sources
Authors: Goldman Geoffrey H.
Published: December 2020

The propagation of signals from elevated sources in the lower audio band (30–500 Hz) are simulated and processed to obtain angle of arrival (AOA) estimates using a small acoustic array. The propagation of the signals are simulated using ray tracing through a stratified atmosphere that is implemented with a finite difference time domain method described by Pierce. The wind and temperature profiles are modeled using Monin-Obukhov similarity theory. The ground reflection is modeled using a two-parameter ground impedance model developed by Attenborough. The spatial coherence of the signals at the array are handled using a statistical model developed by Kozick et al. Basically, the coherence at difference microphones is reduced based upon the range of the source and distance between microphones. The source is modeled using a harmonic structure with no atmospheric or spherical attenuation. This is reasonable since the amplitude of sources is often not known. The AOA of the simulated signals are estimated using a beamforming algorithm and analyzed.
Sound source localizations using various microphone arrays
Authors: Xiang Ning
Published: December 2020

Estimating directions of arrival (DoAs) of multiple sound events still posts challenges in acoustic source localization. This paper reviews recent development on model-based direction-of-arrival analysis using three different microphone array configurations, in situations involving potentially multiple concurrent sound sources. The array configurations include a sparse arrangement consisting of two microphones, coprime linear microphone arrays, and spherical microphone arrays. Formulation and evaluation of prediction models are of central importance in coping with these challenges. These three array configurations are all used to solve a two-level inferential problem of sound source enumeration and direction of arrival estimation. The prediction models based on specific array configurations are evaluated upon experimental data derived from pertinent array processing in order to select the simplest such model that can adequately describe the experimental data, thereby enumerating first the concise number of sound sources, then their DoA information. This paper reviews the prediction models recently established for the three microphone arrays, the two levels of inference, and analysis results. This paper will highlight the importance of the prediction models for the model-based analysis of complex sound environments with potentially multiple concurrent sources.
Representing sonar target spectral features using a two-dimensional Gabor wavelet
Authors: Kubicek Bernice , Sen Gupta Ananya , Kirsteins Ivars
Published: December 2020

We present an alternate representation of sonar spectral features with popular machine learning techniques for automated target classification. Sonar target recognition suffers from feature uncertainties due to unpredictable environmental parameters: changing sound speed profiles, inhomogeneous propagation of acoustic waves, interference and delayed echoes due to multipath effects, ambient ocean noise and reverberation, and signal deformation due to reflections from the seafloor, sea surface, and the Doppler effect. These parameters are further dependent on target orientation and may combine in a nonlinear fashion, making target classification near impossible. We propose a representation of sonar spectral features using the two-dimensional Gabor wavelet as a kernel filter. This extracts highly informative features specific to a target, regardless of orientation. We validate the robustness of our representation against feature uncertainties by comparing the classification performance of three machine learning techniques—a support vector machine, random forest tree, and a neural network—trained on the raw spectrogram (acoustic color) versus the Gabor-filtered feature space through resulting confusion matrices. We will provide classification results of public domain experimental field data. [This research is funded by the Office of Naval Research under Grant No. N00014-19-1-2436.]
Enhanced automated recognition of underwater mine-like objects through environmentally adaptive fusion of detectors, features, and classifiers
Authors: Brandes T. Scott , Ballard Brett
Published: December 2020

The complexity of the natural underwater environment creates a challenging arena in which to find underwater mines. In this work, we demonstrate that automated mine-like object detection tasks are greatly facilitated by a comprehensive fusion process. Our approach begins with characterization of the seafloor based on textures within synthetic aperture sonar (SAS) imagery and uses this to exploit information from the available sensors, multiple detector types, measured features, and target classifiers, to facilitate mine-like object recognition. Our approach is able to adapt as environmental characteristics change, including the ability to recognize novel seabed types. We then adaptively retrain classifiers through active learning in these novel seabed types resulting in improved mitigation of challenging environmental clutter as it is encountered, and develop a segmentation constrained network (SCN) algorithm which enables increased generalization abilities for recognizing mine-like objects in both under-represented and novel, unseen environments in available training data. Additionally, we present a fusion approach that allows us to combine multiple detectors, feature types spanning both measured expert features and deep learning, and an ensemble of classifiers, for the particular seabed mixture proportions measured around each detected target. [Work supported by the Office of Naval Research.]
High frequency source depth localization using deep neural network
Authors: Yoon Seung Hyun , Yang Haesang , Seong Woojae
Published: December 2020

Localization of high-frequency sources in underwater is a difficult problem because the propagation model is increasingly sensitive to environmental parameters as the frequency increases. A deep learning approach is proposed to estimate the depth of a high-frequency underwater source using a single hydrophone trained on real data. A residual neural network is trained by a spectrogram of measured signal and estimates the depth of the source as a regression problem. The method is applied to data collected during the shallow water acoustic variability experiment 2015 in the northeastern East China Sea and compared with the results of the frequency difference matched field processing which uses 16 sensors. It was also validated that the trained model can display the generalized results for the signals measured at other times or at similar settings but different source-receiver location. As a result, the neural network is able to more accurately estimate the depth of high-frequency source and shows the features found by the network from real data are effective for localization, while the model often fails to generate accurate replicas.
Research on active noise control and intensity with Professor Jiri Tichy 1984–2000
Authors: Swanson David C.
Published: December 2020

Before Widrow [1] published the filtered-x algorithm in 1985, Warnaka et al. had a working prototype of a feedforward ANC which also pre-filtered the error path [2]. Tichy's role in this early patent was to break down the system into transfer functions that would align the LMS updates in time. Tichy also was an early investigator in acoustic intensity. By the mid-1990s, a robust frequency-domain ANC system was developed that combined both ANC and intensity to study the power flow and energy conversion in an ANC system [3]. In the early years of ANC, there was much controversy on how the additional energy from a secondary source could result in less energy radiated from a duct driven by a primary source. By using an Intensity error spectrum in a frequency domain ANC system, the power flow (active intensity) was minimized at various positions inside the duct to reveal how the active secondary source uses impedance to govern the radiated energy. This put the controversy to rest and provided clear objective evidence of how sound is actively “cancelled” or more precisely, how controlling waveguide impedance can control radiated sound power. Its an honor to have worked with Jiri.
Instantaneous frequency and its applications
Authors: Suzuki Hideo
Published: December 2020

The instantaneous frequency (IF) and envelope (IE) analysis of signals is very useful in various fields. In this paper, three examples of applications are presented. (1) Representing signals by IF and/or IE. Since signals before and after allpass filtering have the same frequency spectra, there is no way to distinguish them by the spectrum analysis. However, IF and/or IE may show clear differences between them. It is interesting that IF at the onset of a sinusoidal burst signal is twice the frequency of the sinusoid (JAES, September 1980). (2) Analyzing vibratos of violin sounds recorded in CDs in order to find out differences of playing styles of virtuosi such as Grumiaux, Oistrakh, Perlman, and Stern. Some results show clear differences in the speeds and depths of the frequency modulation (vibrato) (ISMA 2004). (3) Analyzing rotation fluctuations of automobile rotating shafts. An electromagnetic or electrostatic sensor located close to a rotating gear measures a quasi-sinusoidal signal. The IF analysis of this signal gives the rotation frequency and details of its fluctuation structure. Not only the steady state rotation, but transient rotation change analysis of a reciprocating engine at the sequence of idling stop and start (ISS) are also possible (https://www.aandd.co.jp/adhome/pdf/catalog/nvhanalysis/casra.pdf).
Humpback whale song analysis based on automatic classification performance
Authors: Rueda Carlos A. , Ryan John P.
Published: December 2020

Song is a prevalent behavior in humpback whale populations, even in regions that are considered to be foraging habitat such as the Monterey Bay National Marine Sanctuary in the Northeast Pacific, where song is detected nine months out of the year. In this work, we explore various machine learning methods to classify song units, as a basis for studying song structure and its changes. We report on a number of analyses and classification exercises based on linear predictive coding, vector quantization, and machine learning classifiers including Naive Bayes, first-order Markov chain, and Hidden Markov modeling. As a baseline for comparison purposes, the distortion measure used to create the codebooks for vector quantization is itself also used as a means for classification. With classification accuracy ranging from 65% to 83% across the selected methods on a 4.5 h recording involving 5000 unit occurrences over 20 different unit types, we evaluate the effect of several signal processing, clustering, and learning parameters on classification performance with the goal of laying a foundation that can be used to characterize song vocalization at not only the unit level but also below (subunit) and above (phrase, theme, song).
Fractional derivative group shear wave speeds for model-based viscoelastic characterization
Authors: Trutna Courtney A. , Rouze Ned C. , Palmeri Mark L. , Nightingale Kathryn R.
Published: December 2020

We present a method for model-based viscoelastic characterization using shear wave elastography. The shear wave displacement signal is differentiated to a series of fractional derivative orders, and the group speed of the signal at each derivative order is calculated. These speeds are compared to a look up table built from simulations for a given viscoelastic material model. The best-fit material parameters are chosen to minimize the mean square difference between the group speeds from the look up table and experimental measurements across all fractional derivative orders. Various two- and three-parameter viscoelastic material models are tested. The technique is validated in simulations with ultrasonic tracking and demonstrated in three viscoelastic phantoms with material properties that match those associated with different degrees of liver fibrosis. Comparatively, phase velocity curves are computed, and parameters determined by fitting analytic expressions for phase velocity for a given material model. The fractional derivative group speed-based technique gives model parameters with lower mean square error than fitting material model parameters directly to phase velocities. Additionally, we conclude these viscoelastic phantoms are sufficiently characterized by a two-parameter material model and are better characterized by the Linear Attenuation model than the more commonly used Voigt model.
Power law dispersion from shear wave images
Authors: Ormachea Juvenal , Parker Kevin J.
Published: December 2020

Many normal soft tissues exhibit dispersion of shear wave phase velocity that is consistent with power law behavior. This rheology is consistent with the fractional Zener model under assumptions that appear to be realistic for normal liver and other tissues. The phenomenon can be measured using multi-frequency reverberant shear wave elastography (R-SWE). A simultaneous multi-frequency R-SWE field can be accomplished by applying an array of external sources that operate at multiple frequencies, for example, 50, 100, 150…500 Hz, all contributing to the shear wave field produced in the target organ. With estimates of phase velocity across this frequency band, the R-SWE approach can obtain a 2-D power law coefficient (PLC) image. The clinical feasibility of this method has been analyzed by assessing the shear wave speed (SWS) and PLC in phantoms and in vivo human organs. For in vivo liver cases, mean SWS (1.99 m/s, 2.29 m/s, and 2.38 m/s) and mean PLC (0.23, 0.44, and 0.43) were estimated for a thin patient, and for two obese patients, respectively. For these cases, the PLC results may be an additional parameter that could help to differentiate the viscoelastic properties in liver tissue and enhanced image contrast in cases where lesions or pathologies show an altered viscoelastic response compared with normal tissue.
Time-dependent, microscale mechanical properties of acoustically responsive scaffolds using atomic force microscopy and confocal imaging
Authors: Aliabouzar Mitra , Davidson Christopher D. , Wang William Y. , Kripfgans Oliver D. , Fowlkes J.Brian , Baker Brendon M. , Fabiilli Mario L.
Published: December 2020

Acoustic droplet vaporization (ADV) has been used to modulate delivery of regenerative molecules from acoustically responsive scaffolds (ARSs), which are composite fibrin hydrogels containing payload-carrying, phase-shift emulsions. Here, we studied the micromechanical properties of ARSs including stiffness as well as elastic and shear moduli over 7 days post-ADV. ARSs, containing dextran-loaded perfluorohexane (PFH) emulsions (diameter: 6 mm) embedded in fluorescently labeled fibrin gels, were exposed to acoustic pressures above the ADV threshold (2.2 ± 0.2 MPa ) at 2.5 MHz. The compressive stiffness as well as elastic modulus of fibrin gels (i.e., without emulsions) and ARSs (pre- and post-ADV) were measured via force-spectroscopy and the Hertz model, respectively. The measured stiffness was lowest (1.9 ± 0.5 mN/m) in regions adjacent to the PFH emulsions and highest (16.0 ± 4.4 mN/m) in regions adjacent to the ADV-generated bubbles. Fibrin compaction at the bubble–fibrin interface was observed using time-lapsed confocal imaging and correlated with bubble growth at the time points studied here. In addition, different ADV-generated bubble responses in ARSs will be discussed using time-lapsed confocal imaging. Elucidating the mechanical microenvironment within the ARS could be used to control mechanically induced, cellular processes and further the understanding of ADV-triggered drug delivery for regeneration.
Feasibility of a single-transducer harmonic motion imaging using frequency-based simultaneous multiple harmonic oscillation excitation pulses
Authors: Hossain Md. Murad , Konofagou Elisa
Published: December 2020

Single-transducer harmonic motion imaging (ST-HMI) uses a single transducer to generate the harmonic motion at a particular frequency by modulating excitation pulse duration and then, estimate the motion by collecting tracking pulses in-between the excitation pulses, unlike the conventional HMI which uses focused ultrasound and an imaging transducer. Instead of oscillating at a single frequency, the objective is to use ST-HMI for simultaneously exciting the tissue at multiple frequencies. Six excitation pulses per period were selected by sampling a continuous signal which was generated by summing sinusoids with fundamental and harmonics of 100 Hz and 200–1000 Hz, respectively. A mean peak to peak displacement (MP2PD) image was generated by a weighted average of P2PD at each frequency with a weighting factor derived from the Fourier transform. The new method is evaluated by imaging four inclusions (INC, Young's modulus: 6, 9, 32, and 75 kPa) embedded in 18 kPa background (BKD) and HIFU ablated excised canine liver. The MP2PD image successfully differentiated all four inclusions with R2 = 0.99 of the linear regression between the MP2PD ratio of BKD to INC versus Young's modulus ratio of INC to BKD. The MP2PD image detected the ablated region with the MP2PD ratio of non-ablated versus ablated regions of 1.64. These results demonstrate the feasibility of simultaneously exciting the tissue at multiple frequencies. Ongoing studies entail the translation of this new elasticity imaging method of detecting breast masses in humans.
On the origin of frequency power-law for tissue mechanics in elastography
Authors: Sinkus Ralph , Annio Giacomo , Franck Gregory , Holm Sverre
Published: December 2020

The imaginary part of the complex shear modulus in tissue is not negligible. In liver the phase angle (ranging between 0 and 1) is about 0.2 while in kidney it is about 0.3. The presence of dispersion can have its origin either in a constitutive loss—i.e., absorption of energy—or in scattering of the wave and hence represents an apparent loss. Since dispersion in tissue follows over a wide range a frequency power-law, fractional order derivative models such as the springpot model are well suited to fit the data in the clinically accessible range of 30–200Hz. They, however, do not provide a fundamental understanding of whether loss is due to friction and hence conversion to heat, or due to material heterogeneities and thus scattering. Models such as ODA are able to relate the observable frequency power-law to the spatial distribution of scatterers. If loss in low-frequency elastography were solely due to scattering, this would render the method extremely powerful in characterizing for instance blood vessel architecture in oncology. To distinguish whether the measured prominant loss in porcine tissue (phase angle ∼0.4) is originating from absorption or scattering, we use MR-Spectroscopy to measure absolute temperature via the resonance-frequency-shift between water and methylene, at precisions better than 0.1 °C. Temperature should increase theoretically by about 1/2 °C at an amplitude of 10 μm, 500 Hz, and an exposure of 1000 s, which is not observed. This points towards scattering as the main mechanism for wave attenuation.
Justification for power laws and fractional models
Authors: Holm Sverre
Published: December 2020

Wave equations with non-integer derivative operators describe attenuation which increases with frequency with other powers than two, unlike ordinary wave equations. It is desirable to try to understand what properties of, e.g., biological tissue that give rise to this behavior. The main attenuation mechanisms of standard acoustics are heat conduction and relaxation, as well as structural and chemical relaxation. They have fractional parallels and the first one is heat relaxation described by fractional Newton cooling due to anomalous diffusion. The most important mechanism is however the fractional parallel to structural relaxation. Instead of one there are multiple relaxation processes with a distribution of relaxation times that follows a power-law distribution, possibly indicating fractal properties. The distribution also has a relationship to the Arrhenius equation, indicating a link to chemical relaxation, albeit a quite speculative one. The multiple relaxation model may also be formulated as a hierarchical polymer model. Time-varying non-Newtonian viscosity and a medium with a fractal distribution of scatterers can also give rise to power law behavior. Existing models in sediment acoustics such as the grain shearing model and the Biot poroelastic model can also be reformulated with fractional operators. These approaches are presented in the hope of progressing towards an understanding of whether fractional wave equations give clues to some deeper reality, or if they are just a compact phenomenological description.
Influence of stickiness on structure function of biology cells
Authors: Tran Quang , O'Brien William D. , Han Aiguo
Published: December 2020

Structure function (SF) is critical in improving the accuracy of quantitative ultrasound (QUS) and tissue characterization. Existing SF models in the field of QUS tissue characterization are based on a hard-sphere assumption where the inter-scatterer potential consists solely of a repulsive hard core. This paper investigates a sticky hard-sphere (SHS) model containing two major characteristics of a real potential, a repulsive potential and an attractive potential. The SHS model assumes two spheres tend to be pulled closer when they are very close to each other. This model can be relevant to biological cells as they are adhesive. This paper presents a theoretical SF for the SHS model with monodisperse scatterer size. To explore the scatterer spatial distribution, a simulation of the SHS model for low, medium, and high volume fractions (0.10, 0.32, and 0.64) at different degrees of the unitless stickiness (0.2, 0.6, and 1.7) over the frequency range from 11 to 105MHz is introduced. A comparison between the theoretical and simulated SFs shows that the two SFs are in good agreement, indicating the theoretical SF describes the scatterer distribution successfully. This study emphasizes the importance and influence of the stickiness parameter for the SF. [Work supported by R01CA226528.]
Avoiding the audio range: Frequencies very high and very low
Authors: Gabrielson Thomas
Published: December 2020

Condenser measurement microphones have been an essential component of acoustic measurements for many years. Although used most often in the “audio range” (20 to 20 000 Hz), they are also capable of quality measurements both well above and well below that range if their limitations are respected and if their outputs are processed carefully. For example, below 20 Hz, the natural low-frequency roll-off provides an automatic pre-whitening for ambient spectra, thereby reducing the dynamic range required, and the roll-off can be compensated by a simple pole-moving filter in post-processing. Well above 20 kHz, diffraction can be significant, the characteristics of an analog-to-digital converter's anti-aliasing filter can be important, and transit time across the surface of the microphone's membrane may not be negligible. Nowhere are these characteristics more important than in measurement of the rise time of acoustic shock waves. If accurate reproduction of the time-domain waveform is important, then any compensation schemes must account for the system phase response as well as the magnitude response. A diffraction-compensation filter can be effective in minimizing waveform over-shoot and a carefully designed baffle can delay the onset of diffraction effects if leading-edge phenomena like peak pressure and rise time are important.
Propellers, motors, and fans
Authors: Gabrielson Thomas
Published: December 2020

Effective demonstrations make immediate visual and aural impact but also inspire discussion, analysis—even argument. From quick study to in-depth examination, inexpensive drone motors and small cooling fans provide excellent objects for classroom demonstration of the acoustics of rotating machinery. One of the most fundamental concepts—blade passage rate—is straightforward to show, to understand, and to relate to the acoustic signature. From there, the process of discovery expands to shaft rotation rate, blade thickness and loading noise, blade/strut interaction, flow noise, gear-mesh noise, electrical-to-mechanical coupling through magnetic-field interaction, and the impact of pulse-width modulation of the drive signal on the acoustic radiation. Processing can be as simple as visualization of a microphone output using an oscilloscope or a spectrogram display; however, the processing can grow to synchronous averaging androtation-rate compensation with the addition of straightforward optical or electrical measurements. A relatively simple apparatus provides a broad spectrum of concepts in a highly visible form.
Acoustic-phonetics demonstrations for classroom teaching
Authors: Arai Takayuki
Published: December 2020

Physical demonstrations using vocal-tract models have been shown to be a quite intuitive way to teach acoustic phenomena on speech production for acoustic phonetics and speech science classes. Several models for different purposes have been developed by Arai within the last 20 + years, including vocal-tract models, sound sources, and lung models [e.g., T. Arai, J. Acoust. Soc. Am. 131(3), 2444–2454 (2012)]. By combining them, the following topics can be effectively taught in virtual and in-person classrooms: visualizing the sound propagation, the relationship between vocal-tract configuration and sound quality; the source-filter theory of speech production; the quantal theory; many-to-one mapping between articulation and sound; many-to-one mapping between sounds and phoneme; and source-filter interactions. Because such demonstrations are highly demanded, the Acoustic-Phonetics Demonstrations (APD) website has been made public (www.splab.net/APD/) to make videos and sound demonstrations available for academic use. The same website contains files of subsets of the vocal-tract models for 3D-printers, so users can download and 3D-print them to have their own models. In addition, some of the models are being used for workshops and exhibitions at museums. The applications of the models are now expanding to multiple areas, such as language learning and clinical situations like speech therapy.
Demonstration and validation of nonlinear acoustic shock wave formation in a renovated waveguide
Authors: McCluskey Connor J. , Langhirt Mark A. , Carder Nick E. , Wade Luke A.
Published: December 2020

When acoustic waves attain high enough pressure amplitudes, the wave speed becomes amplitude-dependent, causing the wave to steepen. If the amplitude is high enough, a shock is formed. Shock formation is commonly covered in nonlinear acoustics courses, but it is difficult to demonstrate experimentally in a classroom setting. Dr. Isadore Rudnick designed a nonlinear waveguide demonstration, as recalled by Dr. Robert Keolian [J. Acoust. Soc. Am. 145(3 Pt. 2), 1682 (2019)]. In his setup, a high amplitude driver inputs an acoustic plane wave into a long PVC pipe. At the Pennsylvania State University, a similar waveguide was built by Dr. Lauren Falco as part of her research on nonlinear jet noise. The waveguide was then used as part of an assignment in a laboratory class taught by Dr. Steven Garrett. However, the waveguide has not been used for almost 10 years. This demonstration apparatus has been restored to working order and was validated by measuring the nonlinear generation and decay of harmonics at three locations along the pipe by varying the peak pressure and frequency of the sinusoidal input. This paper will demonstrate the formation of shock waves using this apparatus.
Richard Lyon's early years on the faculty of MIT's Department of Mechanical Engineering
Authors: Pierce Allan D.
Published: December 2020

Richard Lyon joined the faculty in 1970, but was associated with the ME Department for several years. Stephen Crandall, the Head of the Applied Mechanics Division, had instituted various graduate courses, including one taught by Lyon (BBN) and another taught by Miguel Junger (CAA). Allan Pierce joined as an Assistant Professor in 1966 and was tasked with teaching a graduate course on wave propagation. Lyon had emerged as the principal exponent of statistical energy analysis (SEA), and several MIT students did theses supervised or co-supervised by Lyon. Dick came as a professor in 1970. At the same time he founded Cambridge Collaborative with Jerry Manning, a fellow BBN employee and a former MIT student. Lyon, after joining the faculty, instituted several new research programs, loosely classified as architectural acoustics and noise control. The present talk focuses in part on Lyon's influence on Allan's career during the time they overlapped at MIT and gives some perspective on Lyon's style and leadership. Dick's work on acoustical scale-modeling and the theses he supervised during his early years on the faculty were of great interest to Allan. Dick prompted the work with Wayne Kinney on the field experiments in South Boston on the propagation of noise from low-flying helicopters into urban canyons. He also prompted Allan into attacking the problem of propagation around a three-sided barrier, and it was Dick who palmed off his job as associate editor of JASA onto Allan and thereby cemented his commitment to the ASA.
Application of dual-stage exhaust system using an expansion chamber and resonator for formula SAE
Authors: Philipson Yuval , Lawless Martin S.
Published: December 2020

Typical vehicle mufflers utilize a series of expansion chambers and resonators to reduce engine noise. Both components behave like acoustic filters by changing the impedance of the exhaust system. Expansion chambers act as low-pass filters, which mitigate noise above a cut-off frequency determined by the geometry of the chamber. Meanwhile, resonators target specific frequencies to attenuate like a notch-filter. The present work explored tuning a muffler system containing an expansion chamber and a resonator to reduce engine noise of a Formula SAE racecar. The exhaust system design was completed using custom MATLAB scripts, Ricardo WAVE, and iterative prototyping. After determining the frequencies where the engine produced maximum sound output, the components were fabricated to damp the amplitude of the offending frequencies. The transmission loss of the prototype exhaust system was tested in an anechoic chamber by measuring the frequency responses of each separate component and the entire system. Based on this experimentation, the exhaust system had an expected overall transmission loss of 45 dB. Installed on the vehicle, the operational transmission loss was 18 dB. This discrepancy is likely due to operational conditions that could not be replicated in the laboratory experiment, such as increased temperature and gas flow.
Near to far field relationship of crackle-related events in military aircraft jet noise
Authors: Vaughn Aaron B. , Gee Kent L. , Leete Kevin M. , Downing J. M.
Published: December 2020

Crackle perception in supersonic jet noise is attributed to the presence of acoustic shocks in the waveform. This study uses an event-based beamforming method to track shock events as they propagate from the near to the farfield of a high-performance military aircraft operating at afterburner. Near-field events are propagated via a nonlinear model and compared with far-field measurements. Comparisons of overall sound pressure level and spectra validate the use of the nonlinear model. The skewness of the time-derivative pressure waveform, or derivative skewness, a metric indicative of jet crackle perception, is greatly overpredicted for nonlinearly propagated waveforms. Cross-correlation coefficients of waveform segments centered about the near-field beamformed events reveal that for farther aft angles, near-field events are more related to far-field measurements. Waveform observations show that shock-like events in the near field that are more spiked in nature tend not propagate into the far field. However, near-field, large-derivative events with broader, high-pressure peaks nonlinearly steepen and form shocks in the far field that are likely responsible for crackle perception.
Forming clusters of multiple sounds improves talker identification in an auditory scene
Authors: Yost William A. , Pastore M. Torben , Robinson Philip
Published: December 2020

In recent papers, we have shown that listeners perceive differences in the size of a small auditory scene (<4 sources) for short-duration sounds (e.g., consonant-vowel, CV, pairs) presented at about the same time, but such differences are not perceived for larger scenes. Spatial separation of a small number of sound sources affects performance much more than spatially separating a larger number of sound sources. We studied conditions when the number of sound sources is small, but the number of sounds (CVs) is larger. For example, listeners are poor at determining if a target talker is the same as a cue talker when the target is presented at one sound-source location and several distractor talkers are each presented from different sound-source locations. If all distractor talkers are “clustered (mixed)” at a single sound source spatially separated from the target sound source, then listeners are better at determining if the target talker was the same as the cue. Several additional scenarios were tested, all indicating that “clustering” sounds into a small number of sound sources improves target-talker identification compared to when sounds are presented from a larger number of sound-source locations. [Work supported by grants from NIDCD and Facebook Reality Laboratories.]
Deep learning of the binaural masking level difference
Authors: Smith Samuel S. , Akeroyd Michael A.
Published: December 2020

The binaural masking level difference (BMLD) is the improvement in the detection of a signal in noise observed for different interaural configurations. Durlach [J. Acoust. Sci. Am. 1206–1218 (1963)] derived equations that accurately predict much of the human BMLD psychophysical data. We trained a deep neural network to predict BMLDs, as calculated with Durlach's equations, based on waveforms of a 500 Hz signal in a white noise each presented from different locations. Crucially, the network was constrained via nodes configured to embody informative representations (Iten etal., 2018; arXiv:1807.10300). The deep neural network accurately predicted BMLDs for stimuli within a simulated azimuth and for stimuli with interaural time differences (ITDs) outside the range of a human head. Further, even though the model was not designed to imitate neural biophysics, we discovered that the dynamics of latent nodes bore similarities with published data on neural ITD tuning and rate-level responses to BMLD stimuli. The work demonstrates how advances in deep learning can be used to consolidate theoretical and experimental approaches to binaural detection.
Effect of auditory spatial attention in rear side
Authors: Teraoka Ryo , Sakamoto Shuichi , Cui Zhenglie , Suzuki Yôiti , Shioiri Satoshi
Published: December 2020

When human listeners direct the auditory selective attention to a specific direction, the listener can easily extract target sound from this direction, even under the noisy environment (commonly known as the cocktail-party effect). Although the auditory spatial attention can be directed to any directions around the listeners including rear side, it is still unclear how much the auditory spatial attention in rear side influences this phenomenon. In the present study, we investigated the effect of auditory spatial attention directing to the location behind the listener in a multi-talker environment and compared between this result and the previous result in front of the listener. For the purpose, the word intelligibility was measured for the target speech among non-target speech sounds spatially distributed around the target. The target sound was presented from the direction where the listener attended. To control the listener's attention, we manipulated the probability of target presentation directions or indicated the target direction a priori. The results revealed the improvement of word intelligibility by directing attention to a direction in the rear side, similarly to the effect of attention in the front side. This suggests that there is no directional dependency in the effect of auditory spatial attention.
Numerical modeling of ultrasonic leaky Lamb wave propagation in screen pipes
Authors: Gong Xinyue
Published: December 2020

Screen pipes completion is often used in unconsolidated sandstone reservoirs to prevent formation sand from entering wellbore. However, the screen pipes can be blocked by the formation sand, leading to reduced output of oil. Here a technology based on attenuation of ultrasonic leaky Lamb waves is used to evaluate the sand accumulation outside the screen pipes. A three-dimensional parallel finite-difference time-domain numerical method is developed to investigate the attenuation in the case of a screen pipe surrounded by water or sediment. The attenuation pattern determines the presence of screen holes and the acoustic impedance of the medium outside the screen pipes. The study demonstrates the feasibility of the leaky Lamb wave technology to evaluate sand accumulation outside screen pipes.
The mental cost of repairing errors in speech perception
Authors: Winn Matthew B. , Teece Katherine
Published: December 2020

When evaluating a listener's ability to hear speech in a challenging condition, an experimental challenge is determining whether an utterance was heard correctly or whether it was heard incorrectly and then mentally repaired. Mentally transforming incorrect perceptions into “correct” responses is not visible in intelligibility scores, but is likely a major part of what makes listening effortful for people with hearing loss, and therefore there is a need to design tests that track the occurrence and mental cost of making corrections during speech perception. A series of studies is presented which gathers evidence of the mental cost of repairing errors using pupillometry. Stimuli were explicitly designed to induce different types of cognitive repair so that the ensuing mental cost/listening effort can be measured as it unfolds over time, even without major changes in intelligibility. Results show that different errors result in significantly different amounts of effort. Major findings include quick bursts of effort for phonetic repairs, larger prolonged bursts of effort for entire-word repairs constrained by context, and a substantial increase in effort for errors that result in semantic incongruity across an utterance. Results are discussed with regard to implications for clinical interpretation as well as study design.
Passive velocity estimation of remotely-controlled vehicles via Doppler tracking
Authors: Oelze Eden , Singer Jonah , Tabak Gizem
Published: December 2020

The performance of remotely-controlled (RC) vehicles in recreational activities, such as RC cars, boats, planes and drones, has increased dramatically with the increased energy density of lithium polymer and Nickel metal hydride battery technologies. As a result, RC cars capable of land speeds in excess of 100 mph are available in hobbyist-class vehicles. This work presents an experimental and analytical setup for measuring the land-, water-, and air-speed of such RC vehicles using passive signal processing of acoustic recordings of the vehicles in operation. The high-efficiency DC brushless motors used in these platforms emit strong harmonic structure that can be efficiently measured with Doppler-tracking. The harmonic structure of the recorded acoustic signals allow passive velocity estimation using quasi-periodic signal detection and period estimation techniques based on pitch detection methods in the time and frequency domain. Preliminary results yielded successful velocity recovery based on Doppler tracking using a pilot signal, and demonstrated the correlation between the speed profile of the vehicle and acoustic harmonics. Future work will include an analytical model and set of experiments for passive velocity measurement suitable for high school and undergraduate physics laboratory exercises.
Investigating the effect of off-axis bearing estimation on the range-Doppler characteristics of transmit waveforms
Authors: Tidwell Matthew , Hague David A.
Published: December 2020

The spectral filtering an active sonar waveform undergoes due to the frequency dependent beampatterns of a projector encodes information about the target's bearing relative to the main response axis. For a given transducer and transmit spectrum there exists an optimal angle of operation at which the Fisher Information (FI) of the target bearing estimate is maximized. For relatively low fractional bandwidth Linear Frequency Modulated (LFM) waveforms, the angle of maximum FI is solely determined by its center frequency [Tidwell and Buck, in SSPD (2019)]. This facilitates steering the region of maximum bearing estimation precision by changing the center frequency of the LFM waveform without steering the transducer's main response axis. This research expands on these previous efforts and investigates both the transmit waveform impact on bearing estimation performance and the spectral filtering impact on the waveform's range-Doppler ambiguity function. This analysis is performed using the Multi-Tone Sinusoidal Frequency Modulated (MTSFM) waveform model, which possesses a discrete set of parameters that are adjusted to synthesize a broad class of waveform types [Hague, in IEEE AES (2020)]. Low fractional bandwidth MTSFM waveforms have a negligible impact on bearing estimate precision. However, the transducer's spectral filtering has a profound impact on the waveform's range-Doppler characteristics.
Underwater sound source characteristics from down-the-hole pile driving
Authors: Guan Shane , Reyff James
Published: December 2020

Unlike conventional impact pile driving technique in which a pile is hammered into the sediment a top hammer, down-the-hole (DTH) piling technique uses a combination of percussion and drilling mechanism with the hammer acting directly on the sediment to advance the pile. Small cuttings and debris broken by the hammer are flushed out by the air exhaust through the drill pipes. DTH piling is considered one of the fastest ways to drill through hard rock and install piles, and is increasingly used by industries. However, underwater noise generated from DTH piling is poorly studied. Here we present two DTH pile driving studies: pile driving of 18- and 42-inch steel pipe piles on Biorka Island and at Skagway, Alaska, respectively. The results show that single strike sound exposure levels are 146 and 164 dB re 1 μPa2 s at 10 m for the 18- and 42-in. piles, respectively, the root-mean-square sound pressure levels at this distance are 162 and 178 dB re 1 μPa for the 18- and 42-in. piles, respective piles. Our results are compared to those from other studies. The potential effects on marine fauna resulting from this complex sound field needs further investigation.
Variable refrigerant flow HVAC units in classrooms—Calculations versus measurements
Authors: Manley David , Pippitt Logan
Published: December 2020

An elementary school renovation and addition design seeking LEED certification included use of a variable refrigerant flow system for classroom heating and cooling. Previous challenges have been identified with use of these types of units, most notably that sound data provided by equipment manufacturers is non-standardized to AHRI or other United States or internationally recognized HVAC sound data collection procedures. Methods for estimating corrections to the non-standardized noise data developed by others were deployed to estimate room noise levels in design phases, but compliance with LEED noise level requirements of 40 dBA was not able to be satisfactorily determined. Post-construction field measurements were conducted, and results will be presented and compared to design calculations.
Achieving CHPS for classroom acoustics: Project case study
Authors: Rosentel William , Holst Peter
Published: December 2020

This presentation will provide insights from a recently completed, budget-driven new construction high school project in California, which pursued the CHPS (Collaboration for High Performance Schools) Designed program. The nation-wide CHPS criteria include acoustical performance pre-requisites for project recognition under the indoor environmental quality metric. The acoustical criteria address sound isolation, room acoustics, HVAC background noise levels, and environmental noise intrusion. The pre-requisite acoustical criteria applied to this project (EQ 14.0—2014 CA-CHPS Criteria v1.02) will be reviewed along with discussion of the optional EQ 14.1 Enhanced Acoustical Performance. The CHPS criteria reference ANSI 12.60 and describe testing methods regarding compliance evaluation. However, interpretation of the criteria is still required. Improvement to the criteria language and testing requirements are of pragmatic interest to achieving the CHPS design intent. The presentation will overview the required documentation provided during the Design Phase and a summary of acoustical recommendations to achieve the criteria, which have cost implications and required coordination across design team members. Review of the final design, post-construction testing and findings will be provided, highlighting the components of the acoustical CHPS criteria that were readily achieved, and those components where implementation of the design must be carefully overseen during construction.
STEM in action: One progressive school's project-based approach to improving their acoustical environment
Authors: Browne Sean , Browne Spencer
Published: December 2020

They go by many names: Progressive Schools, 21st Century Schools, Project-Based Schools. These schools do not conform to the test-driven curricula often mandated by local school boards but have student-centered curricula with an emphasis on developing portfolios and exhibiting tangible products as evidence of learning. These schools are rapidly increasing in numbers and leading an evolution in education. The schools that practice project-based learning have more laboratories and maker spaces. They will be more hands-on in nature and very collaborative. They have dynamic needs from the physical space, having to accommodate individual, small-group, and large-group activities. However, they will not be immune from the detriments of excessive background noise and reverberation. The nature of these types of schools will present challenges to the acoustical designs that are needed to ensure that “learning is easier, deeper, more sustained, and less fatiguing.” A case study will be presented of such a school and how their need for an acoustical remediation became their class project.