bluuebunny/crossref_metadata_2025 huggingface dataset:
A highly efficient approach to model acoustics with visco-thermal boundary losses
Authors: Berggren Martin , Noreland Daniel , Bernland Anders
Published: October 2018

For devices such as hearing aids, microphones, micro loudspeakers, and compression drivers, thermal and viscous boundary layer effects are often highly noticeable. These effects can be modeled in the linear regime by the linearized, compressible Navier-Stokes equations. However, the need for resolution of the very thin boundary layers typically makes numerical solutions of these equations computationally very expensive. Based on a boundary-layer analysis, we have derived for the pressure Helmholtz equation what appears to be a new boundary condition that accurately takes visco-thermal boundary losses into account. The model is valid when the wavelength and the minimum radius of curvature of the wall is much larger than the boundary layer thicknesses. In the special case of sound propagation in a cylindrical duct, the model collapses to the classical Kirchhoff solution. We assess the model in the case of sound propagation through a compression driver, a kind of transducer that is commonly used to feed horn loudspeakers. The transmitted power spectrum through the device calculated numerically using our model agrees extremely well with computations using a hybrid model, where the full linearized, compressible Navier-Stokes equations are solved in the narrow regions of the device and the pressure Helmholtz equations elsewhere. However, our model needs two orders of magnitude less memory and computational time than the more complete model.
A functionally relevant measure of spatial release from masking in children with bilateral cochlear implants
Authors: Peng Z. Ellen , Litovsky Ruth
Published: October 2018

The ability to segregate speech from noise is an important skill for children as they navigate everyday noisy environments. Spatial release from masking (SRM) is a measure of benefit observed when target speech is co-located versus spatially separated from maskers. SRM is typically studied with target-maskers in front versus maskers displaced to fixed angles towards the side. Children fitted with bilateral cochlear implants (BiCIs) typically show smaller SRM than children with normal hearing (NH), even for target-masker angular separation of 90°, and when monaural head shadow cues exist. Here, we used an open-set corpus that has high informational masking and better mimics realistic listening situations for children. First, SRM was measured by adapting target-masker separation, and quantified as the minimal angular separation needed to achieve 20% improvement in target intelligibility. Second, SRM was measured for target-masker separation of 180°. Preliminary results suggested that, in the BiCI group, all children achieved 20% SRM with a target-masker angular separation smaller than 180°. With the full 180° target-masker separation, children in the BiCI group achieved a much larger SRM (6–8 dB) than previously reported while NH children’s SRM was larger. Acoustic cues available through CI processors will be discussed. [Work funded by NIH-NIDCD.]
Eulerian motion magnification applied to structural health monitoring of wind turbines
Authors: Cygert Sebastian , Czyzewski Andrzej
Published: October 2018

Several types of defects may occur in wind turbines, as physical damage of blades or gearbox malfunction. A wind farm monitoring and damage prediction system is built to observe abnormal vibrations of elements of wind turbine: blades, nacelle, and tower. Contactless methods are developed which do not require turbine stopping. In this work, structural health monitoring of a wind turbine is evaluated using a conversion from the captured and processed video to the acoustic signal, employing the method of Eulerian motion magnification in video. It was assumed that this task can be achieved using a stabilized high-speed video camera only, directed at the wind turbine without any additional sensors mounted on windmill blades or on its body. Moreover, the developed vector sound intensity probe was used for spatial measurements in order to recover the vibration modes of wind turbines. Finally, statistical methods were applied to the processing of computed features reflecting vibrations in order to determine wind turbine technical condition. The developed method was evaluated empirically in real wind farm. [Research was subsidized by the Polish National Centre for Research and Development within the grant “STEO—System for Technical and Economic Optimization of Distributed Renewable Energy Sources,” No. POIR.01.02.00-00-0357/16.]
Perception of vowels with missing formant information
Authors: Nenadic Filip , Coulter Pamela , Kiefte Michael , Nearey Terrance M.
Published: October 2018

The dominant formant-based model of vowel perception has been challenged by several whole-spectrum approaches. Recent arguments in favor of the importance of cues other than formant frequencies come from a study by Ito et al. [J. Acoust. Soc. Am., 110, 1141–1149] in which suppressing either of the first two formants did not radically change the identification of Japanese vowels. The present study replicates the experiment using the larger vowel system of the English language. Visual inspection shows that even when a formant is suppressed, listener responses do not deviate as much as would be expected if formants were the sole cue for vowel identification. However, quantitative analyses indicate that participant agreement in which vowel they heard is significantly lower when they respond to stimuli with suppressed formants. Additionally, the suppressed formant value becomes a less important predictor of vowel identity. These changes in responses become even larger when stimuli (original, F1-suppressed, and F2-suppressed vowels) are presented together rather than in separate blocks. Taken together, these results show that, although formants are not the only correlate to vowel identity, they seem to be the most important.
Short-term, not long-term, average spectra of preceding sentences bias consonant categorization
Authors: Stilp Christian
Published: October 2018

Phoneme perception is influenced by spectral properties of surrounding sounds. For example, listeners perceive /g/ (lower F3 onset) more often after sentences filtered to emphasize high-F3 frequencies, and perceive /d/ (higher F3 onset) more often after sentences filtered to emphasize low-F3 frequencies. These biases are known as spectral contrast effects (SCEs). Much of this work examined differences between long-term average spectra (LTAS) of preceding sounds and target phonemes. Stilp and Assgari (2018 ASA) revealed that spectra of the last 500 ms of precursor sentences, not the entire LTAS, predicted biases in consonant categorization. Here, the influences of Early (before the last 500 ms) versus Late (last 500 ms) portions of precursor sentences on subsequent consonant categorization were compared. Sentences emphasized different frequency regions in each temporal window (Early = low-F3 emphasis, Late = high-F3 emphasis, and vice versa) naturally or via filtering. Entire-sentence LTASes predicted that SCEs would not bias consonant categorization, but instead responses were biased by the spectrum of the Late window. This was replicated when the Early window did not emphasize either frequency region but the Late window did. Results endorse closer consideration of patterns of spectral energy over time in preceding sounds, not just their LTAS.
Effects of spatiotemporal manipulation of audiovisual speech on the perception of prosodic structure
Authors: Fuhrman Robert
Published: October 2018

Work in audiovisual speech processing (AVSP) has established that the availability of visual speech signals can influence auditory perception by improving the intelligibility of speech in noise (Sumby and Pollack, 1954). However, exactly which aspects of visible signals are most responsible for this enhancement remains an open question, although convergent evidence along several lines suggests that visible information may reflect a common articulatory-acoustic temporal signature, and that the multi-modal availability of this temporal signature is at the root of this effect. We evaluated this hypothesis in a perceptual study using simple talking face animations whose motion is driven by a signal derived from the collective motion of perioral structures of an actual talker. We applied spatial and temporal manipulations to the structure of this driving signal using a biologically plausible model that preserves the smoothness of the manipulated trajectory, and tested whether these kinematic manipulations influenced the perception of linguistic prominence, an important component of the timing and rhythm (prosody) of speech. The data suggest that perceivers are sensitive to these manipulations, and that the cross-correlation between the acoustic amplitude envelope and the manipulated visible signal was a strong predictor of the perception of prominence.
Acoustic features of intelligible speech produced under reverberant environments
Authors: Kubo Rieko , Akagi Masato
Published: October 2018

Clear speech has been shown to have an intelligibility advantage over conversational speech in reverberant environments. Speech produced in reverberant environments is also reported to be more intelligible than ones produced in normal environments. Speakers adapt to the environments by modifying their articulation, and acoustics of speech. The speech produced under reverberant conditions should be modified similarly with the clear speech. Identifying the distinctive features which are shared between these speech types gives insights into which acoustic features are robust cues even in reverberant environments. In the present study, we investigated voices uttered by speakers who produced Japanese words under reverberant conditions (T60 = 1 s–5 s). Speech intelligibility tests, and acoustic analyses were performed. The results showed that, first, speech produced under long T60 is more intelligible in reverberant environments. Second, the intelligible speech has expanded vowel space with high F2 for front vowels and low F2 for back vowels, and high F1 for open vowels and low F1 for close vowels. Brief formant transitions were also found. These articulatory/acoustic modifications are likely to be enhancements of significant perceptual cues. The acoustic/articulatory features of each vowel become clearer (hyper-articulated speech; i.e., clear speech.) Moreover, perceptual compensation to reduce co-articulation effects should become easier.
Distinguishing Dick from Jane: Children's voices are more difficult to identify than adults' voices
Authors: Fecher Natalie , Cooper Angela , Johnson Elizabeth
Published: October 2018

Previous research on talker recognition has focused on the processing of talker identity in adult voices; however, little is known about how listeners identify child voices. This study examined adult listeners’ ability to differentiate and identify child voices (2.5-year-olds) and adult voices. In Experiment 1, native English-speaking listeners completed an AX voice discrimination task with both child and adult voices. Results revealed that listeners were significantly worse at discriminating between child voices relative to adult voices, regardless of the fact that child voices were mixed gender and adult voices were all female. In Experiment 2, we examined whether listeners could learn to identify child and adult voices. Adult listeners completed an adaptive training paradigm, where they learned to identify 4 child voices on one day and 4 adult voices on a separate day. Preliminary results indicate that with training, listeners can learn to identify voices from both age groups above chance. However, listeners were still faster at learning and more accurate at identifying adult relative to child voices. Taken together, these findings are an initial step towards understanding how talker recognition is influenced by the acoustic-phonetic characteristics and articulatory capabilities that vary with talker age.
Effects of emotional tones of voice on the acoustic and perceptual characteristics of Mandarin tones
Authors: Chang Huishan , Young Shuenn-Tsong , Li Pei-Chun , Chu Woei-Chyn , Ho Cheng-Yu
Published: October 2018

Emotional tones of a speaker’s voice and lexical tones involve similar acoustic correlates, but only lexical tones could change the meaning of a word in tonal languages. The purpose of this study is to investigate the interaction between these two types of tonal variations by examining the acoustic and perceptual characteristics of the four Mandarin tones across different emotional tones of voice. In experiment 1, acoustic analyses of fundamental frequency, mean amplitude, and duration was conducted on a syllable with the four tones produced in a carrier phrase with four different emotional tones of voice (anger, fear, happiness, and sadness). The same acoustic measures were also taken on the Mandarin neutral tone produced with the four emotional tones. In experiment 2, speech materials from experiment 1 were used to investigate the effects of the emotional tones on the perception of Mandarin tones. The results showed that all four emotional tones had significant effects on the acoustics and perception of Mandarin tones. These findings suggest that emotional tones of voice impact both acoustic and perceptual characteristics of lexical tones.
Study on the relationship between modulation spectral features and the perception of vocal emotion with noise-vocoded speech
Authors: Zhu Zhi , Miyauchi Ryota , Araki Yukiko , Unoki Masashi
Published: October 2018

Previous studies about vocal-emotion recognition with noise-vocoded speech showed that temporal modulation cues provided by the temporal envelope play an important role in the perception of vocal emotion. To clarify the exact feature of temporal envelope that contributes to the perception of vocal emotion, a method based on the mechanism of modulation frequency analysis in the auditory system is necessary. In this study, auditory-based modulation spectral features were used to account for the perceptual data collected from vocal-emotion recognition experiments using noise-vocoded speech. At first, the modulation spectrogram of the emotional noise-vocoded speech was calculated by using an auditory-based modulation filterbank. Then, ten types of modulation spectral features were extracted from the modulation spectrograms. Finally, modulation spectral features and the perceptual data were compared to investigate the contribution of temporal envelope to the perception of vocal emotion with noise-vocoded speech. The results showed that there were high correlations between modulation spectral features and the perceptual data. Therefore, the modulation spectral features should be useful for accounting for the perceptual processing of vocal emotion with noise-vocoded speech. [Work supported by JSPS KAKENHI Grant Number JP. 17J08312, and Grant in Aid for Scientific Research Innovative Areas (No. 18H05004) from MEXT, Japan.]
Bearing and range tracking with a two-hydrophone ocean glider
Authors: Küsel Elizabeth T. , Siderius Martin
Published: October 2018

A Slocum glider fitted with two hydrophones separated by a distance of approximately 3 feet recorded sperm whale sounds during an experiment off the west coast of the island of Sardinia, Italy, in the summer of 2014. Time difference of arrival analysis of their echolocation clicks provided bearing tracks. It was also found that the left-right ambiguity inherent of the bearing estimation process could be broken by the natural oscillation in glider heading. More recently, a controlled experiment on a quiet lake with a known fixed acoustic source was devised to investigate unambiguous bearing estimation and possible ranging. Simple target motion analysis (TMA) using the glider’s position data resulted in range estimates of only a few hundred meters short of the true source location. Analysis of the acoustic data on the other hand, presented challenges to satisfactory TMA performance. Overall, it was found that simple bearing-only TMA analysis is possible with two-hydrophone acoustic data and small angular change of a few degrees in the heading of the observing platform. Results will be discussed with implications to marine mammal population density estimation studies, since the ability to estimate direction and range of sound-producing animals could improve estimation of detection probabilities.
Wavenumber domain acceleration for stripmap fast factorized backprojection beamforming
Authors: Marston Timothy , Plotnick Daniel
Published: October 2018

Synthetic aperture sonar (SAS) imaging is frequently used in conjunction with autonomous underwater vehicles (AUV's) to perform high resolution wide-area surveys. Wave action and currents perturb the trajectories of AUV's performing these surveys and these perturbations have important ramifications for the SAS beamforming process. Generalized beamforming algorithms operating in the time domain are very flexible with regard to trajectory non-linearities, but they also tend to have a higher computational cost than alternative frequency domain algorithms. Of the generalized beamformers one of the more efficient is fast factorized backprojection (FFBP), which leverages sub-aperture processing and a series of coordinate transformations to improve computational efficiency. FFBP can be used to beamform SAS data, however many SAS systems make use of a real aperture to boost range potential. The existence of a real aperture implies that a frequency domain beamformer could be used to bypass the first few stages of FFBP without loss of generality; however, standard frequency domain SAS beamforming algorithms are not compatible with the FFBP framework. A wavenumber domain beamformer compatible with the early-stage FFBP framework is derived and beamforming results for the modified FFBP algorithm are compared with the standard approach that operates entirely in the time domain.
Monitoring of macroalgae (kelp) farms with autonomous underwater vehicle-based split-beam sonar
Authors: Fischell Erin , Stanton Timothy K. , Kukulya Amy , Lavery Andone C.
Published: October 2018

The long-term goal of ARPA-E's MARINER (Macroalgae Research Inspiring Novel Energy Resources) program is to increase the scale of offshore kelp aquaculture so that biofuel may be derived from macroalgae. An autonomous underwater vehicle (AUV) system including acoustic, optic, and environmental sensors has been developed for the purposes of monitoring these large-scale kelp farms. The primary sensor for observing farm infrastructure such as horizontal longlines (from which the kelp grows) as well as kelp growth is a broadband split-beam sonar system. Structural information, such as droop in the longlines, is available from time-of-flight of the acoustic echoes. Growth of kelp is quantified from both time-of-flight and volume backscattering echo data. Experimental results from ocean measurements taken with the REMUS 100 AUV on longlines are presented, along with preliminary processing techniques for estimating longline position and macroalgae extent for vehicle control and farm mapping purposes [work supported by ARPA-E.]
A hybrid time and wavenumber domain algorithm for generalized beamforming with circular synthetic aperture data
Authors: Marston Timothy , Plotnick Daniel
Published: October 2018

Synthetic aperture sonar systems typically scan along a linear trajectory, however autonomous underwater vehicles (AUV's) provide a useful platform for performing scans along more complicated trajectories with specific advantages. One example is the circular scan, which provides superior wavenumber coverage and resolution for images reconstructed near the circle center. A variety of approaches have been put forward for beamforming synthetic aperture data collected along a circular trajectory, but for images that span a significant fraction of the circle radius, accelerated time-domain approaches such as fast-factorized backprojection (FFBP) have been suggested. The computational requirements for generating a fully sampled image collected around a circular aperture are extremely large, however, even for FFBP. This is primarily because of the extremely small pixel size required to maintain adequate spatial sampling as larger portions of the aperture are coherently fused in the later stages of the FFBP algorithm. A method is presented for replacing the later stages of the algorithm with a series of spectral mappings, retaining the generality of the beamformer while improving computational efficiency.
Empirical modelling for derived metrics as function of sound exposure level in marine pile driving
Authors: Müller Roel A. , Ainslie Michael A. , Halvorsen Michele B. , Lippert Tristan
Published: October 2018

To protect marine life, piling activities at sea are subject to regulations on sound emission. Different regulatory authorities base different action criteria based on different statistics of the emitted sound pressure. Modelling efforts to predict these metrics have achieved mixed success. While the sound exposure level (SEL) can be predicted relatively well, it has proven harder to model the peak sound pressure level (Lpk) accurately. It would therefore be valuable to have a reliable way of estimating Lpk, based on a prediction of SEL. Correlations between SEL and Lpk and between SEL and rms sound pressure level (Lrms) are obtained from measurements during piling of the Luchterduinen wind farm off the Dutch west coast, and are used to assess the applicability of correlations found at other wind farms. A metastudy using data from Luchterduinen as well as the German Bight gives a more robust trend line for use at other North Sea sites. Lrms is computed in two different ways, involving the 90 % energy signal duration on the one hand and the effective signal time duration (Teff) on the other. The value of Lrms based on Teff is found to be more robust. [Work sponsored by BOEM.]
Analysis on acoustic longitudinal horizontal correlation of air-to-water transmission
Authors: Zhang Lingshan , Peng ZhaoHui , Wang GuangXu
Published: October 2018

Spatial correlation is an important characteristic of underwater sound field, which is relevant to the detection of aerial targets from underwater. But compared with waterborne sources there are few researches about airborne sources. In order to perform further analysis on the air-to-water sound transmission in shallow water, State Key Laboratory of Acoustics, Institute of Acoustics, conducted an experiment in the South China Sea in March, 2013. During the experiment, multi-frequency signals transmitted by a hooter hung on a research ship were received by a horizontal line array (HLA) which laid on the seabottom, and signals far from 9.8 km were received successfully. Based on data recorded in the experiment, the longitudinal horizontal correlation coefficients of underwater sound field excited by airborne source at different distances with the frequency is 128 Hz are obtained, which have evident oscillation structure as horizontal spacing increases. The mathematical expression is derived based on the normal mode theory and gives a better physical explanation for the oscillatory behavior of the experimental longitudinal horizontal correlation.
Three dimensional finite element modeling of scattering by objects at rough interfaces
Authors: Gunderson Aaron M. , Isakson Marcia J.
Published: October 2018

Fully three-dimensional finite element models for buried objects and objects at interfaces have been extended to incorporate interface roughness. Near field results are solved using a fully scattered field formulation, in which all fields in the absence of the target are applied and the target scattering is solved. Results are extended to the far field through the Helmholtz-Kirchhoff integral, using a numerically determined Green’s function approach. Interface roughness is applied using a modified power law wavenumber spectrum. Previous model demonstrations evaluated the scattering in the flat interface limit, in which background fields were prescribed analytically. Now, the presence of the surface roughness forces background fields to be evaluated and prescribed numerically. Such models have strong applicability for predicting scattering by objects buried within or resting on a rough seafloor interface. Model results are compared with various experimental and other modeled results, demonstrating model validity over a wide frequency range. [Work supported by Applied Research Laboratories IR&D and ONR, Ocean Acoustics.]
Measuring with noise? We can do better!
Authors: Müller-Trapet Markus , Hoeller Christoph
Published: October 2018

It has long been established that correlation-based measurement techniques, using, e.g., maximum length sequences and swept sines, outperform classical methods based on random Gaussian noise. Among the advantages of these modern techniques are better rejection of background noise and reduced measurement duration to achieve similar or better precision. These advantages are especially interesting in room and building acoustics, where many measurement positions typically have to be covered and background noise is often an issue, especially when measuring sound transmission loss or velocity level differences. Unfortunately, there is currently no provision in the ASTM standards on room and building acoustics that would allow the use of these modern measurement methods. To demonstrate the advantages of these methods, this contribution will present an example of measurements of the apparent sound transmission loss, i.e., measurements of sound pressure level differences and reverberation times. In addition to the standardized measurements according to ASTM E336, all measurements were repeated with maximum length sequences and swept sines. The results will be compared and the advantages of the modern techniques will be highlighted.
Design of a new test chamber to measure the absorption, diffusion, and scattering coefficients
Authors: D'Antonio Peter , Jeong Cheol Ho , Nolan Mélanie
Published: October 2018

This presentation will describe the design for a new 384 m3 test chamber that will allow the measurement of the random incidence absorption coefficient, according to ISO 354, the scattering coefficient, according to ISO 17497-1, the diffusion coefficient, according to ISO 17497-2 and the normal incidence low frequency absorption coefficient, according to ISO 10534-2. The rev room design incorporates optimal modal dimensional ratios in accordance with (T. Cox, P. D’Antonio & Avis, J. Audio Eng. Soc. Vol. 52, No. 6 (June 2004)), both boundary and hanging panel diffusers to allow satisfactory diffusivity, in collaboration with the research at DTU. Diffusivity will be verified using a reference absorber, consisting of 100 mm porous absorber with a 100 mm cavity. A sufficiently large reflection free volume is provided in the chamber for diffusion coefficient scale model measurements. The diffusion goniometer and 12 m2 absorber samples are rotated in accordance with test. Scattering coefficient measurements are made according the ISO 17497-2 and the correlation method, using correlated polar responses. A steel and concrete lined low frequency impedance tube measuring 600 mm x 600 mm x 5.8 m long and 7 tons will be used to measure absorption from 25 to 250 Hz.
New ASTM ratings for quantifying low and high-frequency impact insulation in laboratory testing
Authors: LoVerde John , Dong David W.
Published: October 2018

The authors have recently published [J. Acoust. Soc. Am. 141, pp. 428–440 (2017)] a two-rating method for evaluating impact sound insulation, in which the low and high-frequency components of the floor are evaluated independently. Although originally described for field testing, the ratings can be applied to laboratory testing. ASTM draft classifications have been submitted for low and high-frequency versions of Impact Insulation Class, named LIIC and HIIC, respectively. The scope and use of the new ratings are explained.
Look—Do you see the noise leaking through that ceiling?
Authors: Madaras Gary
Published: October 2018

Oftentimes, acousticians must convey complex, three-dimensional, acoustical phenomena that occur within and between rooms in buildings to architects, interior designers and other visually oriented people. The message can be lost during translation from quantitative acoustics metrics and their acronyms to the design and intersection of actual building elements such as walls and ceilings. The current phase of the Optimized Acoustics Research Program focuses on turning sound absorption and sound isolation performance visual by using color mapping. Much like a thermal imaging camera shows differences in surface temperatures, a sound intensity probe is being used to produce high definition color sound mapping of noise transmitting through acoustical ceiling systems and sound reflecting off or being absorbed by surfaces with different absorption coefficients. This measurement method helps to bridge the gap between the technical, quantitative side of acoustics and the visual side of design in an impactful and memorable way.
Lessons learned from acoustically tracking baleen whales on the Navy’s Pacific Missile Range Facility
Authors: Helble Tyler A. , Henderson E. E. , Martin Stephen W. , Alongi Gabriela C. , Martin Cameron R. , Ierley Glenn
Published: October 2018

Detection, localization, classification, and tracking of marine mammals has been performed on the U.S. Navy’s Pacific Missile Range Facility (PMRF) for over a decade. The range hydrophones are time-synchronized, have excellent spatial coverage, and monitor an area of approximately 1200 km2. Even with these ideal assets, there are hidden challenges when attempting acoustic density estimates of baleen whales on the range. This talk will cover lessons learned from tracking several species of baleen whales on the range over the last decade.
Using detection received level as a guide for odontocete density estimation
Authors: Hildebrand John , Frasier Kaitlin E. , Solsona Berga Alba
Published: October 2018

Odontocete echolocation clicks have been used for density estimation using cue-counting. We present an approach for assessment of the appropriate threshold for click detection based on the click received sound-pressure-level distribution. Under the assumption of random spatial distribution of echolocating animals with respect to the sensor, the number of detections should decrease with increasing received level. This pattern is verified by simulation modeling, even after incorporating diving behavior and sound production directionality. When measured received level distributions show peaks at values above the detection threshold, errors in the detection process are the most likely explanation. Potential remedies involve setting a higher detection threshold and/or fully characterizing both missed and false positive rates.
Estimating population densities of temperate, insectivorous bats based on automatically recorded calls
Authors: Milchram Markus , Bruckner Alexander
Published: October 2018

Estimating population density based on automatically recorded calls is a key topic in bioacoustics, as individual recognition of animals is impossible. Several recently developed models do not require individual recognition but nevertheless allow to estimate density. However, there is a need to test these models on empirical data. Here, we used generalized random encounter models (gREM) to estimate population densities based on automatically recorded bat calls. To check the validity of the derived estimates, we fit Royle-Nichols models to species detection/non-detection data. Estimates of the two models were compared to each other and to estimates from published studies. The estimates of both models and literature estimates were within the same order of magnitude. Both models give reliable estimates of population density. However, we provide some cautionary notes for practical use: Bats which enter the detection sphere from above might bias results of gREMs, as the model simplifies the detection sphere to a two-dimensional area. On the other hand, reduction to detection/non-detection data in Royle-Nichols models results in information loss, which could limit their applicability in common species. Finally, we recommend to consider species behaviour carefully when applying one of the tested models.
Measurements of underwater noise north of Spitsbergen using deep-sea recorders
Authors: Tollefsen Dag , Buen Helge
Published: October 2018

This paper presents results from year-long passive acoustic recordings in the seasonally ice-covered ocean north of Spitsbergen (Svalbard archipelago) from July 2016 to June 2017. Two moorings were deployed by FFI, each with an AMAR Ultra Deep acoustic recorder (JASCO Applied Sciences) equipped with a single hydrophone. The moorings were deployed and retrieved during open-water conditions and remained during periods of partially to near fully ice-covered conditions. We present results from analysis of the acoustic data for ambient noise spectra and statistics, and discuss characteristics of the spectra in relation to environmental factors including ice cover, wind and ocean waves. Seasonal noise spectra are compared with historic measurements from the eastern Arctic. Components of the sound field including transients due to ice, marine mammals, and anthropogenic noise will also be discussed.
Bone guided-wave ultrasonography: How far are we from clinical implementation?
Authors: Le Lawrence H. , Tran Tho N. , Nguyen Kim-Cuong T. , Sacchi Mauricio D.
Published: October 2018

Bone guided-wave ultrasonography uses mechanical waves to study the long cortical bones. Long cortex has soft tissues above and marrow below acting like an ultrasound waveguide. The reverberations of the longitudinal and shear waves within the waveguide interfere constructively to generate energetic ultrasonic guided waves (UGW) travelling along the cortex. The UGW can be generated and recorded using an axial transmission technique with the transmitter and receiver deployed axially along the axis of the long bone on the skin’s surface. The UGW thus acquired can be analyzed to provide information relevant to thickness and mechanical properties of the long bone. In this communication, we present an update of our research efforts on bone guided-wave ultrasonography including data acquisition, multichannel signal processing, bone modeling, and implementation of inversion algorithms to recover cortical thickness and mechanical parameters from UGW data. We also present some technical challenges, which will call for the joint effort of the bone ultrasound community to advance the science.
Detection of fast and slow waves propagating through porous media
Authors: Wear Keith A.
Published: October 2018

Porous media can support two longitudinal waves, which often overlap in time and frequency domains. Each wave has its own attenuation coefficient and phase velocity. These properties are related to volume fraction of solid phase, tortuosity, viscous characteristic length, and elasticity. Therefore, knowledge of individual wave properties is useful for characterizing porous media. Accordingly, methods for recovering separate reconstructions of fast and slow waves are of interest. The transfer function of a porous sample may be expressed as a weighted sum of two complex exponentials. The Modified Least Squares Prony’s (MLSP) method may be used to recover the two individual components for non-dispersive media. Porous media are dispersive, however. The MLSP method may be augmented with curve-fitting (MSLP + CF) to account for dispersion. An alternative approach, based on Bayesian probability theory, is also powerful for recovering fast and slow waves. These approaches have been tested in through-transmission experiments on cancellous bone samples. Bayesian and MLSP + CF approaches successfully separated fast and slow waves and provided good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains.
Ultrasonic backscatter evaluates the variability of bone in pregnant women
Authors: Li Boyi , Li Dan , Ta Dean
Published: October 2018

Pregnancy and lactation-associated osteoporosis (PLO) is characterized by the deterioration of bone tissue and the fractures during pregnancy without any underlying disorders. This study attempted to investigate the variability of bone in pregnant women. The ultrasonic backscatter experiments were performed in Shanghai Changning Maternity & Infant Health Hospital. A total of 896 subjects were divided into four groups gestational age from 11th to 39th week, calculated apparent integrated backscatter coefficients (AIB) and spectral centroid shift (SCS). The estimated bone mineral density (Est. BMD) was measured using a medical ultrasonic transmission instrument. The body mass index (BMI) was calculated basing on height and weight. The results showed that AIB preformed a decreasing trend with the increasing of gestational age, the mean value in 37-39th-week group decreased 2.07 dB comparing with the 11-13th-week group, p<0.001. The SCS mean value in 37–39th-week group shifted 21.66 kHz than the 11–13th-week group, p<0.001. The Est. BMD mean value in 37–39th-week group decreased 0.05 g/cm2 than the 11–13th-week group, p<0.001. The BMI increased with gestation age, the mean value in the 37–39th-week group was higher than the 11–13th-week about 4.19 kg/m2, p<0.001. One of the reasons for these results was that pregnant women provide nutrition for the fetus, resulting in decreased bone tissue along with gestational age increasing. These results suggest that ultrasonic backscatter method might have a potential to diagnosis PLO.
Effect of high intensity focused ultrasound transducer F-number and waveform non-linearity on inertial cavitation activity
Authors: Bawiec Christopher , Hunter Christopher , Kreider Wayne , Maxwell Adam D. , Khokhlova Vera A. , Sapozhnikov Oleg A. , Khokhlova Tatiana D.
Published: October 2018

Enhanced chemotherapeutic drug delivery has been shown using pulsed high intensity focused ultrasound (pHIFU) without contrast agents. The threshold of these inertial cavitation effects has recently been correlated to the formation of shocks at the focus. The shock amplitude and corresponding peak negative pressure (p-) are primarily determined by the transducers F-number with less focused (higher F-number) transducers producing shocks at lower p-. Here, the dependence of inertial cavitation activity on F-number was investigated in gel phantoms using passive cavitation detection (PCD) and high-speed photography. HIFU transducers with the same aperture but different F-numbers (0.77, 1.02, and 1.52), operable at three driving frequencies (1 MHz, 1.5 MHz, and 1.9 MHz), were utilized with driving conditions consisting of 1 ms pulses delivered every second and p- from 1 to 15 MPa. Broadband noise emissions recorded by PCD were batch-processed to extract cavitation probability and persistence while concurrent imaging was performed in the focal pHIFU region. At the same p-, both PCD metrics and the imaging revealed enhanced cavitation activity at higher F-numbers. These results support the use of less focused, smaller-footprint transducers for achieving desired cavitation-aided drug delivery. [Work supported by NIH R01EB023910, K01DK104854, R01EB007643, and RFBR 17-54-33034.]
Feeling gassy? Modifying the oxygen partial pressure of a fluid using acoustic droplet vaporization and different droplet concentrations
Authors: Su Haili , Mercado-Shekhar Karla P. , Benton Rachel P. , Zhang Bin , Sharma Sneha , Haworth Kevin J.
Published: October 2018

Nucleating acoustic droplet vaporization reduces the dissolved gas content in a fluid. The objective of this study was to determine if the change in the partial pressure of oxygen (Po2) could be modulated by adjusting the concentration of micron-sized perfluoropentane droplets. The droplets were manufactured using high-speed shaking and size-isolated using differential centrifugation (1 to 6 μm in diameter). Droplets were diluted in saline with a Po2 of 154 mmHg and pumped through a 37°C flow phantom at 40 mL/min. The concentration ranged from 3.5×106 to 3.5×108 droplets/mL. A 5 MHz focused transducer insonified droplets at peak negative pressures of 4.05 MPa with a 500-Hz pulse repetition frequency and 5-cycle pulse duration. The Po2 was measured downstream of the insonation region. At the lowest droplet concentration, the Po2 was reduced to 129 mmHg. As the droplet concentration was increased, the Po2 was reduced further. The reduction was in agreement (intra-class correlation and Pearson correlation coefficients greater than 0.9) with the model reported by Radhakrishnan et al. (2016, Ultrason. Sonochem.). At the highest droplet concentration, the Po2 was reduced to 31 mmHg. These results demonstrate that ADV with varying droplet concentration modulates the oxygen partial pressure in a fluid.
Characterization of lipid-encapsulated microbubbles for delivery of nitric oxide
Authors: Shekhar Himanshu , Palaniappan Arunkumar , McDaniel Cameron , Hassett Daniel J. , Holland Christy K.
Published: October 2018

Nitric oxide (NO) is a potent bioactive gas capable of inducing vasodilatory, anti-inflammatory, and bactericidal effects. The short half-life, high reactivity, and rapid diffusivity of NO make therapeutic delivery challenging. The goal of this work was to develop a technique to sequester NO within lipid-shelled microbubbles. Microbubbles loaded with either NO alone (NO-MB) or with NO and octafluoropropane (NO-OFP-MB) were synthesized by high-shear mixing of 1 mL lipids with either 1 mL of NO, or a mixture of 0.9 mL NO and 0.1 mL OFP. The size distribution and attenuation coefficient of NO-MB and NO-OFP-MB were measured using a Coulter counter and a broadband acoustic attenuation spectroscopy system, respectively. The payload of NO in the microbubbles was assessed using an amperometric micro-electrode sensor. Co-encapsulation of NO with OFP increased the number density, attenuation coefficient, and temporal stability of lipid-shelled microbubbles. However, the amount of NO loaded in NO-MB and NO-OFP-MB was similar (0.91 ± 0.03 μM and 0.93 ± 0.1 μM, respectively). These results suggest that NO can be encapsulated within lipid-shelled microbubbles. However, co-encapsulation of OFP does not enhance the NO payload or the temporal stability, despite an increase in attenuation and number density of lipid-shelled microbubbles.
Musical drumhead damping using externally applied commercial products
Authors: Worland Randy , Miyahira William
Published: October 2018

Snare drums and tom toms used in drum sets often produce an undesirable high frequency ringing sound when struck. Drummers have historically applied DIY damping solutions to address this ringing, placing objects such as wallets and tape on the heads. A large variety of inexpensive commercial products is now available to dampen drums in a more controlled manner. The most commonly used products consist of small adhesive pads that can be placed directly on the drumhead at desired locations, either singly or in combinations. An experimental investigation of the ringing drumhead modes and the effects of the damping pads is reported. Decay rate measurements indicate that the (3,1), (4,1), and (5,1) modes often contribute the most to the ringing sound, and that these modes are strongly affected by the damping pads. Another class of commercial dampener consists of thin annular rings of Mylar that conform to the perimeter of the drum head. These free-floating rings produce a similar damping effect, but dissipate energy through a different physical mechanism. Experimental results for both types of dampeners are presented and discussed in terms of viscoelastic and air-layer damping mechanisms, respectively.
Take me out to the ballgame: The acoustics of the softball bat piano
Authors: Russell Daniel A.
Published: October 2018

As a multimedia supplement for a recent article “Acoustics and Vibration of Baseball and Softball Bats” [Acoustics Today, 13(4), 35–42 (2017)] the author created a “softball bat piano” and played the tune “Take Me Out to the Ballgame.” The bat piano is a collection of softball bats, clamped at the handles, selected for their barrel frequencies. It is played by striking the bat barrels with a softball. The structural modes of the hollow cylindrical barrel of an aluminum or composite bat are responsible for the trampoline effect which affects the performance of the bat as it is used for the game of softball. However, the “hoop mode” which gives rise to the trampoline effect is also the source of the bat piano’s audible musical sound. The nature of these cylindrical shell vibrations will be discussed, highlighting similarities to the musical properties of bells and chimes. The influence of bat construction and materials on the “hoop frequency” will be explained, along with the process of selecting bats with a range of frequencies wide enough to form a musical scale. If time permits, video of additional musical selections will be shown.
How beatboxers produce percussion sounds: A real-time magnetic resonance imaging investigation
Authors: Greer Timothy , Blaylock Reed , Patil Nimisha , Narayanan Shrikanth S.
Published: October 2018

Beatboxing is a musical artform in which performers use their vocal tract to create percussion sounds. Sometimes beatboxers perform as a part of an ensemble, using their vocal tract to provide a beat for other musicians; other times, beatboxers perform alone, where they might sing and produce percussion sounds simultaneously. We present methods in real-time magnetic resonance imaging (rtMRI) that offer new ways to study the production of beatboxing sounds. Using these tools, we show how beatboxers can concatenate intricate articulations to create music that mimics the sound of percussion instruments and other sound effects. The rtMRI methodology reveals how different beatboxers play their vocal folds to perform characteristic “clean” or breathy styles. By using rtMRI to characterize different beatboxing styles, we show how video signal processing can demystify the mechanics of artistic style.
Weather focused challenges for continuous monitoring of military noise
Authors: Klein Jordan D. , Bunkley Steven , Patel Sahil G. , Brown Richard D. , Ray Jason D. , Barr Jesse M. , Blevins Matthew G. , Lyons Gregory W. , Netchaev Anton
Published: October 2018

Domestic military installations generate high levels of noise due to testing and training which leads to annoyance and complaints from surrounding communities. This necessitates continuous noise monitoring to provide decision makers with the information they need to proactively manage their noise environment. Due to the diverse climates in which military testing and training are conducted (e.g., desert, tundra, and rainforest), monitoring equipment that can operate in a variety of environmental conditions with minimal maintenance and low power consumption is needed. Using existing technologies as a baseline, various iterations of a low-cost acoustic monitor were designed to meet these constraints while minimizing initial investment cost, improving the mean time between failures, and increasing overall system capability. This paper will describe the system developed to provide a rapid deployment option that is robust to extreme temperatures, humidity, and destructive wildlife. A review of operational logs collected during multiple deployments was used to evaluate system performance against benchtop and off-the-shelf solutions. This data demonstrate the reliability of the monitoring stations and the sustainability of their hardware.