bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffuse ultrasound monitoring of stress and damage development on large scale concrete structures
Authors: Larose Eric , Zhang Yuxiang , Moreau Ludovic , Planes Thomas , Obermann Anne
Published: June 2017

This paper describes the use of an ultrasonic imaging technique (Locadiff [1]) for the NDT&E of concrete structures. By combining coda wave interferometry and a sensitivity kernel for diffuse waves, Locadiff can monitor the elastic and structural properties of a heterogeneous material with a high sensitivity, and can map changes of these properties over time when a perturbation occurs in the bulk of the material. The applicability of the technique to life-size concrete structures is demonstrated through monitoring 2 reinforced concrete strutures [2-3]. Locadiff achieved to detect and locate the cracking zones in the core of concrete and monitor the internal stress level in both temporal and spatial domains by mapping the variation in velocity caused by the acoustoelastic effect. The mechanical behavior of the concrete structure is also studied using conventional techniques such as acoustic emission, vibrating wire extensometers, and digital image correlation. [1] E. Larose et al., “Locating a small change in a multiple scattering environment,” Appl. Phys. Lett. 96 (20), 204101 (2010). [2] Y. Zhang et al., “Diffuse ultrasound monitoring of stress and damage development on a 15-ton concrete beam,” J. Acoust. Soc. Am. 139 1691-1701 (2016). [3] Y. Zhang et al., “3D in-situ imaging of cracks in concrete using diffuse ultrasound,” Struct. Health Monitoring, under review (2017).
The defect detection algorithm that combined spectrum entropy with vibrational energy ratio for acoustic inspection method
Authors: Sugimoto Kazuko , Sugimoto Tsuneyoshi , Utagawa Noriyuki , Katakura Kageyoshi
Published: June 2017

We have studied the non-contact and non-destructive acoustic inspection method using airborne sound wave and a laser Doppler vibrometer. Internal defects (crack, peeling etc.) of concrete near the surface are excited by vibrational energy of acoustic radiation. The resonance frequency of flexural vibration of the defect (inside to depth 8-10 cm) of concrete can be measured. By our technique, a non-destructive test is possible from a long distance more than 5 m max to 30 m. The two-dimensional vibration velocity data are measured and processed numerically. An image of the defect is reconstructed by vibrational energy ratio. There was a problem of an optical noise resulting from the leakage of light reception depending on surface state of concrete. To solve it, we introduced “Spectrum Entropy.” The data under influence of an optical noise show a frequency characteristic similar to a white noise. Spectrum entropy is calculated as an information entropy and express white nature of a signal. Therefore, we propose an algorithm that combines spectrum entropy with vibrational energy ratio. Our technique was applied to an experiment with a real concrete structure (bridge). The defective part was extracted as an image and the validity of our method was confirmed.
Mapping of ultrasonic Lamb-wave field in elastic, layered structures using acoustic and laser probes
Authors: Klieber Christoph , Brill Thilo
Published: June 2017

In the oil and gas industry, the nondestructive evaluation of cemented steel pipes in subterranean wells commonly involves the use of ultrasonic, guided Lamb waves. These measurements help ensure that the cement annulus between the rock formation and the steel pipes provide hydraulic isolation between different depth zones of the well. Such techniques employ the excitation of leaky flexural and extensional waves inside the highly contrasting steel layer to distinguish solids from liquids in the inaccessible region outside the pipe. Furthermore, the annular cement layer may exhibit defects such as cracks or channels which may compromise zonal isolation. We present laboratory measurements using piezo-electric needle probes and laser interferometry, as well as comparative modeling results along spatial and temporal dimensions to visualize and quantify leaky-Lamb-wave propagation for a variety of homogeneous liquid and solid layers behind a steel sheet in planar and cylindrical geometries. We characterize several annular materials with compressional velocities, which are higher or lower than the Lamb phase speed to demonstrate the effect on mode dispersion and attenuation. Furthermore, we study the effects on transmission and reflection of Lamb waves at discontinuities such as conduits in the inaccessible layer.
Linear broadband nonreciprocity in waveguides using distributed feed forward control
Authors: Sasmal Aritra , Grosh Karl
Published: June 2017

Nonreciprocal waveguides can exhibit different properties depending on the direction, amplitude, and frequency content of an incident wave. These systems are the focus of intense recent research activity in engineering and in acoustics in particular driven by exciting applications such as cloaking, subwavelength anechoic termination, and full-duplex communication. In biology, nonreciprocity has been identified in cochlear mechanics and is hypothesized to play a role in its filtering and nonlinear processing of sound. Although there has been a surge in the study of unidirectional energy propagation in acoustic media, most of the work has been limited to non-linear effects and/or narrowband non-reciprocity. However, nonlinear effects generate additional harmonics, complicating the approach, and narrowband non-reciprocity constrains the bandwidth that can be used. We have developed the theory for linear nonreciprocal broadband acoustic waveguides using a distributed feed forward control scheme that exhibits significant broadband, nonreciprocity while maintaining stability. We discuss the different systems for which the paradigm may be adopted along with the theoretical formalism to predict the stability and dispersion relations for this class of waveguides.
Load identification by coherence analysis of structural response
Authors: Milana Silvia , Sinibaldi Giorgia , Marino Luca , Culla Antonio
Published: June 2017

Aim of this paper is the identification of uncorrelated forces acting on a structure based on a coherence analysis of the structure response, performed entirely in operative condition. In order to identify the position and the amplitude of the applied load only the responses of the structure and the experimental FRF are required. The proposed procedure consists of three steps. First, the number of acting loads is established by the analysis of the responses coherence, second the position of the acting forces is identified using an index obtained by the knowledge of experimental FRF and of the responses of the structure, then, the amplitude of the acting forces is computed in correspondence of the excited points. The procedure is tested by two experiments. First experiment consists in the excitation of a complex structure in several places with an instrumented hammer. The identification is performed by the accelerations measured on a set of points of the structure itself. The second experiment is carried out by exciting a structure with a fluid flow in a wind tunnel. The accelerations of the structure vibrations and the structure-born acoustic noise are measured and used to identify the fluid pressure acting on the structure.
Sensitivity of the radiated sound power to amplitude dependent damping
Authors: Wuehrl Mario , Klaerner Matthias , Kroll Lothar
Published: June 2017

Using low shear resistant cores in metal plastic composites offers the possibility of an increased damping and therefrom improved acoustic properties of extensive metal sheet structures which are sensitive to vibrations. The damping of the single components in the composite shows an amplitude dependency. Established numerical material models in the finite element method do not consider any amplitude dependency. Therefore, the influence of the damping on the radiated sound power is evaluated numerically for monolithic rectangular steel plates and subsequently extended for the metal plastic composite. The results of the experimental characterization of the amplitude dependency for the components of the composite are described. Relevant parameter ranges are identified and their effect on the sound radiation is outlined.
Experimental characterization of short-glass-fiber polymer composite for vibroacoustic applications
Authors: Zerrad Mehdi , Totaro Nicolas , Rinaldi Renaud G. , Leclerc Quentin , Eller Benjamin
Published: June 2017

In order to design vehicles with diminished CO2/km emissions level, car manufacturers aim at reducing the weight of their vehicles. One of the solutions advocated by the automotive engineers consists in the replacement of metallic parts by lighter systems made of polymer composites. Unfortunately, the numerical simulations set to evaluate the vibratory and acoustic performances of systems made of this kind of materials are often not sufficiently effective and robust so that convincing test/simulation correlations are rarely met. Indeed, for polymer-based materials, numerous parameters affect the vibroacoustic behavior of the system. For the present study, focusing on Polyamide 6 reinforced glass fiber plates (PA6-GF35), it will be demonstrated using DMA (Dynamic Mechanical Analysis) and FAT (Force Analysis Technique) analysis that the viscoelastic properties depend on the temperature and frequency but also on the humidity content. We will compare the FAT method which permits to identify the equivalent complex Young’s modulus of a flat structure as a function of frequency to the DMA measurements which give access to the complex modulus of the intrinsic constitutive materials at small frequency (<20Hz). Finally, the anisotropy of the PA6-GF35 has been evidenced using X-ray tomography images and confirmed by DMA and FAT method analysis.
Vibration of a baffled piezoelectric ceramic circular disk in lower radial modes, with near- and farfield sound radiation
Authors: Storheim Espen , Lunde Per , Vestrheim Magne
Published: June 2017

Accurate knowledge of the sound field generated by an ultrasonic transducer is important in certain applications, such as custody transfer oil and gas flow measurement. Near- and farfield diffraction effects may influence on the measurement result, demanding a need for control of magnitude and phase influences. In many situations, the simplified model of a planar and uniformly vibrating baffled piston is used to approximate the transducer’s sound field. The Rayleigh distance of the piston model is often used as a measure of the near- and farfield transition range. Real transducers typically exhibit a non-uniform vibration distribution at the front, with significant side and rear vibration. It is of interest to investigate the accuracy of the traditional piston and Rayleigh distance approaches for real transducer sound fields. A circular and baffled Pz27 piezoelectric ceramic disk with diameter 12.7 mm and thickness 2.0 mm is studied, operating in air. Finite-element modeling, supported by analytical and numerical modeling, is used to investigate the near- and farfield sound pressure field over the 0-500 kHz range, including radiation at the two lowest radial modes of the piezoelectric disk. Significant nearfield effects are observed well beyond the Rayleigh distance, both on and off the acoustic axis.
Relating ambulatory voice measures with self-ratings of vocal fatigue in individuals with phonotraumatic vocal hyperfunction
Authors: Mehta Daryush , Van Stan Jarrad , Masson Maria Lúcia , Maffei Marc , Hillman Robert E.
Published: June 2017

Advancements in mobile and wearable technologies continue to enhance ambulatory voice monitoring for the improved assessment and treatment of behaviorally based voice disorders. Phonotraumatic vocal hyperfunction is one common behaviorally based voice disorder associated with faulty patterns of chronic vocal behavior that result in vocal fold tissue trauma, such as nodules or polyps. As a result, individuals often exhibit dysphonia and elevated levels of vocal fatigue. This study investigated the relationships between self-ratings of vocal fatigue and ambulatory voice measures in 44 patients with vocal fold nodules or polyps and a control group of individuals with normal voices matched for sex, age, and occupation. Using a smartphone-based ambulatory voice monitor, self-ratings were provided on a visual analog scale at five-hour intervals during the day, and data were continuously recorded from a subglottal neck-surface accelerometer. Voice dosimetry metrics and summary statistics of ambulatory voice measures were derived from accelerometer-based estimates of sound pressure level, fundamental frequency, and spectral and cepstral properties. Given the variance inherent in perceptual judgments, the analyses focused on comparisons between time periods that exhibited differences in self-ratings that were determined to be significant (>19.7 points on a 100-point scale).
Application of laryngeal landmarks for characterization of dysphonic speech
Authors: Ishikawa Keiko , MacAuslan Joel , Boyce Suzanne E.
Published: June 2017

Dysphonia is often a result of laryngeal pathology, which elicits greater aperiodicity and instability in a speech signal. These acoustic abnormalities likely contribute to the intelligibility deficit reported by speakers with dysphonia. Acoustic analysis is commonly used in dysphonia evaluation; however, currently available algorithms focus on describing aspects of the signal that are relevant to perception of voice quality. Signal abnormalities contributing to the intelligibility deficit may be better described by a linguistically-motivated approach. One such approach, landmark-based analysis describes a speech signal with acoustic markers that are relevant to speech production and perception. The analysis further denotes onset and offset of speech events. This study examined the utility of acoustic markers specifically designed to detect laryngeal events for differentiating normal and dysphonic speech signals. In particular, we examined three markers: two markers that detect periodic moments with different acoustic rules, [g] (glottal) and [p] (periodicity); and one marker that detects moments of abrupt F0 change, [j] (jump). The analysis was performed on recordings of the first sentence of the Rainbow Passage from 33 normal and 36 dysphonic speakers. Results suggest that, for the same speech materials, counts of these markers differentiate dysphonic from normal speech.
Vocal turn-taking between mothers and their hearing-impaired infants with cochlear implants
Authors: Kondaurova Maria V. , Reed Jessa , Zheng Qi
Published: June 2017

Normal-hearing (NH) infants participate in social exchanges soon after birth. What does the temporal organization of vocal turn-taking (VTT) look like in infants with hearing loss with cochlear implants? This study examined VTT during spontaneous play in eight dyads of mothers and their hearing-impaired (HI) or age-matched NH infants (mean age 17.4 m at time 1). Dyads came to two sessions, corresponding to 3 and 12 months post-implantation. Analyses demonstrated that although HI infants vocalized less than NH infants, the proportion of vocalizations involved in VTT exceeded that from NH infants at time 1 and was equal at time 2. For vocalizations involved in VTT, there was a higher proportion of simultaneous speech in HI dyads compared to NH dyads at time 1, but the direction reversed at time 2. At time 1, the number of turns was greater in the HI group but decreased compared to the NH group at time 2. Duration of between-speaker pauses (BSP) was shorter in infant-mother compared to mother-infant turns in the NH group only. At time 2, the duration of BSP was shorter in infant-mother compared to mother-infant turns in both groups. The results suggest that infant hearing status affects temporal characteristics of VTT.
Prosodic bootstrapping of syntax from cochlear implant-simulated speech
Authors: Hawthorne Kara E.
Published: June 2017

It has been well-documented that prosodic boundaries often align with syntactic boundaries, and that both infants and adults capitalize on prosodic cues to bootstrap knowledge of syntax. However, it is less clear which prosodic cues—pre-boundary lengthening, pauses, and/or pitch resets across boundaries—are necessary for this bootstrapping to occur. It is also unknown how syntax acquisition is impacted for listeners who do not have access to the full spectrum of prosodic information. These questions were addressed using noise vocoded speech, which simulates speech perceived through a cochlear implant. While pre-boundary lengthening and pauses are well-transmitted through noise vocoded speech, pitch is not. In two experiments, adults listening to noise vocoded speech performed similarly to adults listening to unmanipulated speech in syntax acquisition tasks. This suggests that lengthening and pause cues alone are sufficient to facilitate acquisition of some syntactic structures, and that listeners with cochlear implants may be able to bootstrap syntax using prosody in a similar way as individuals with normal hearing.
Perception of voice gender in children's voices by cochlear implant users
Authors: Guest Daniel R. , Kapolowicz Michelle R. , Montazeri Vahid , Assmann Peter F.
Published: June 2017

Previous research [Assmann et al., J. Acoust Soc. Am 138, 1811 (2015)] investigated normal-hearing (NH) listeners’ ability to discriminate age and gender in children’s speech. Speech stimuli (/hVd/ syllables from 140 speakers between 5 and 18 years of age) were processed using STRAIGHT to simulate a change in perceived gender. Experimental conditions involved swapping the fundamental frequency (F0) contour and/or formant frequencies (FF) to the opposite-sex average at each age level. This research was extended by presenting the stimuli to cochlear implant (CI) users. Preliminary results from two CI users have led to two main conclusions. First, whereas NH listeners used both F0 and FF to discriminate voice gender, CI users relied primarily on F0. Second, NH listeners and CI users demonstrated differential patterns of voice gender misclassification, particularly in the case of young children. NH listeners, while frequently making errors, identified a majority of young boys as male and young girls as female. In contrast, CI users identified most young children as female.
Dyslexia limits listener responsiveness to indexical cues in speech
Authors: Fox Robert A. , Jacewicz Ewa , Long Gayle
Published: June 2017

Recent research has shown that the underlying phonological impairment in dyslexia (DYS) is associated with a deficit in recognizing indexical features in voices of multiple talkers, including talker dialect. This study further examined sensitivity (measured in A-prime) to indexical information using stimuli which varied the nature and the redundancy of acoustic cues. Twenty DYS adults, 20 DYS children and 40 corresponding controls from Ohio listened to three sets of stimuli: unaltered, low-pass filtered (LP) at 400 Hz (retaining voice information but little content), and eight-channel noise-vocoded speech (VS) (eliminating all harmonic information). Listeners identified talker dialect (Ohio, North Carolina) and sex. Compared with controls, performance of DYS listeners was significantly lower although the overall pattern was consistent for both groups: For the degraded stimuli, sensitivity to dialect was greater in VS than in LP, and sensitivity to talker sex was greater in LP than in VS. However, DYS listeners were disproportionally less sensitive to talker sex in VS. Overall, children performed significantly worse than did adults for all three stimulus types. The current results further revealed that individuals with dyslexia are deficient in utilizing indexical features, irrespective of the amount of the acoustic cues available in stimulus speech.
Covert acoustic markers of alveolar-velar stop contrasts in the speech of two-year-old children with and without repaired cleft palate
Authors: Eshghi Marziye , Zajac David
Published: June 2017

The development of backed alveolar stops in children with repaired cleft palate (CP) may be due to reduced maxillary arch dimensions (Zajac et al., 2012; Eshghi et al, 2013). Shriberg et al. (2003) have also suggested that otitis media (OM) may be a marker for backed articulation in children without CP. The present study sought to explore acoustic markers of alveolar and velar stops in two-year old children with and without repaired CP. All children were from American-English speaking families, had competent VP function as determined by nasal ram pressure (NRP) monitoring, and had hearing within normal limits. Speech samples consisted of words with initial alveolar and velar stops. Audio recordings of six children with repaired CP, (2 males, 4 females), seven children with OM (6 males, 1 female), and 13 typically developing (TD) children (7 males, 6 females) were analyzed acoustically. Results indicated that mean first spectral moment was smallest (6.03 kHz) for the alveolar sounds produced by children with CP, followed by children with OM (6.22 kHz), and then by TD children (6.61 kHz) (p = 0.15). These preliminary trends suggest that both maxillary anomalies and/or fluctuating hearing loss may contribute to the development of palatalized stops. [Research reported in this publication was supported by the National Institute of Dental & Craniofacial Research of the National Institutes of Health under Award Number 1R01DE022566-01A1.]
The impact of deictic gesture on vowel acoustics in childhood apraxia of speech
Authors: Connaghan Kathryn , Rusiewicz Heather
Published: June 2017

A growing literature supports the notion that manual gestures and speech are entrained, with one movement modulating the spatiotemporal properties of the other. For instance, Krahmer and Swerts (2007) demonstrated that gestures elicited unintentional prosodic stress production in healthy adult speakers. Understanding this relationship in individuals with motor speech disorders could inform both the underlying neuromotor impairment and the design of efficacious interventions. For example, two of the hallmark characteristics of childhood apraxia of speech (CAS) are atypical prosody and vowel distortions (ASHA, 2007). Given the impact of prosodic stress on vowel formants (e.g., Hay et al., 2006), enhanced prosody elicited through gestures may improve vowel clarity and consistency. The current investigation was designed to explore the relationship between manual and speech gestures in CAS by evaluating the consequences of deictic (pointing) gestures on vowel acoustics. Participants included children with CAS and healthy controls (ages 6-12 years). Vowel formants (F1, F2) were extracted from utterances produced with and without targeted stress and gestures. Metrics of formant centralization, vowel distinctiveness, and consistency of production were compared across stress and gesture conditions and between speaker groups. Preliminary findings suggest the potential of manual gestures to facilitate vowel production in CAS.
Acoustic consequences of speech treatment in children with cerebral palsy
Authors: Chang Younghwa M. , Eldib Sarah , McAuliffe Megan J. , Levy Erika
Published: June 2017

Cerebral palsy (CP) is the most common motor disability in childhood and can severely impact speech intelligibility. However, sparse evidence exists on which to base treatment. The current study examined the acoustic outcomes of Speech-Systems-Intelligibility-Treatment (Levy, 2014), a speech treatment aimed at enhancing intelligibility by targeting increased articulatory-working-space and vocal intensity through child-friendly prompts. Thirteen American-English speaking children with spastic dysarthria due to CP were assigned to a speech treatment group or a control group. Before and after treatment, participants repeated pre-recorded minimal pair nonsense words contrasting only in the initial consonant. Acoustic analysis of the children’s nonsense word productions indicated that on average, duration and sound-pressure-level (SPL) increased for the speech group post-treatment. Similar increases were observed in the control group’s SPL and duration, but to a lesser extent. Thus, preliminary results suggest promising treatment effects on speech acoustics for repeated words. Analyses of fricative-affricate contrasts, and F2 slope changes shed additional light on stability and changes in the speech of children with dysarthria in response to treatment. Additionally, changes in connected speech without a model talker may point to possible transfer of new skills to more spontaneous speech.
Bilinear problems and sparse arrays
Authors: Koochakzadeh Ali , Pal Piya
Published: June 2017

Inverse problems in imaging with sensor arrays often involve estimation of desired parameters (associated with targets or sources) in presence of undesired quantities such as modeling and calibration errors, or uncertainties in accurate modeling of the propagation medium. These errors and uncertainties introduce additional unknown parameters in the measurement model, giving rise to so-called “bilinear problems.” In such models, the measurements collected at the sensor array are linear with respect to the desired parameters, when the nuisance parameters are held constant, and vice versa. In this talk, we will address the question of solving such bilinear problems in a unified manner. Important distinctions will be made between gain/phase calibration errors, and sensor perturbation errors. We will show that while the former gives rise to conventional bilinear models, the latter produces a mixed affine-linear model, with completely different ambiguity sets. The role of sparse arrays and the pattern of repetitive elements in their difference sets will be shown to play crucial roles in determining the number of unknown parameters that can be provably inferred from such models, via clever elimination of nuisance parameters. We will also consider robust convex and non-convex algorithms for solving exact or relaxed versions of bilinear problems and compare their relative performances.
A total generalized variation approach for near-field acoustic holography
Authors: Fernandez-Grande Efren
Published: June 2017

Near-field methods based on microphone array measurements are useful to understand how a source radiates sound. Due to discretization errors, these methods are typically restricted to low frequencies. Sparse approaches have gained considerable attention, as they can potentially recover a seemingly under-sampled signal with remarkable accuracy, extending the valid frequency range. However, near-field problems are generally not spatially sparse, and it is more appropriate to promote block-sparse solutions (i.e. spatially extended) rather than direct spatial sparsity. In this paper, a method is examined that promotes solutions with sparse spatial derivatives. The method seeks spatially extended solutions, valid over a wide frequency range, and suitable to near-fields and extended sources. The methodology is based on a Total Variation approach using higher order derivatives. The frequency range of validity is examined, as well as the robustness to noise. The performance of different finite difference stencils is investigated. Numerical and experimental results are presented, with particular focus on the estimated power radiated by the source. The method is benchmarked against conventional approaches.
Sparse distributed sensor placement via statistical restricted isometry property
Authors: Rogers Jeffrey S. , Edelmann Geoffrey F.
Published: June 2017

Perfect sensor coverage of large ocean volumes is an intractable problem for small N systems. Instead, this paper presents optimal placement of relatively few sensors in order to achieve coherent array processing. The sensor placement will simulate acoustic beam steering despite being a severely underdetermined problem. Utilizing the statistical restricted isometry property (StRIP), with high probability, a stable (invertable) sparse array will be formed. Additionally, sensor placement will be shown with spatial constraints such as improved field of view (resolution and side lobe suppression) in a direction of a priori interest. A comparison of the StRIP optimized network will be made with co-prime samplers, random arrays, and Wichmann and Golomb rulers. [This work was supported by ONR.]
Comparison of multiplicative and min processors for coprime and nested geometries using the Elba Island data set
Authors: Chavali Vaibhav , Wage Kathleen E.
Published: June 2017

Vaidyanathan and Pal describe nested and coprime array geometries that provide significant sensor savings when compared to densely populated Uniform Linear Arrays (ULAs) [IEEE Trans. Sig. Proc., 2010, 2011]. They show that a multiplicative processor can reconstruct the spatial power spectrum from the sparse measurements made by a Nested Array (NA) or Coprime Sensor Array (CSA). Multiplication of the beamformed outputs of two undersampled subarrays eliminates the ambiguity due to aliasing, but requires temporal averaging to mitigate cross terms. Prior work analyzes a multiplicative CSA processor using data from an underwater vertical array deployed near Elba Island [Chavali et al., Asilomar Conf. SS&C, 2014]. Compared to the conventional spectrum obtained with the ULA, the multiplicative CSA spectrum for the Elba data contains endfire interference due to cross terms associated with coherent mode arrivals. Liu and Buck propose an alternative processor, which uses the minimum of the two subarray outputs as the spectral estimate [IEEE SAM, 2016]. This talk compares performance of the multiplicative and min processors using the NA and CSA subarrays designed for the Elba experiment. The NA-min processor produces the best spectral estimate for this scenario. [Work supported by ONR Basic Research Challenge Program.]
Wideband source enumeration and direction-of-arrival estimation using sparse array periodogram averaging in low snapshot scenarios
Authors: Liu Yang , Buck John R.
Published: June 2017

Sparse arrays, such as minimum redundancy arrays and coprime arrays, often exploit the second-order statistics of the propagating field to localize more sources than sensors by constructing an augmented covariance matrix (ACM) from the estimated spatial correlation. The source localization performance largely depends on the number of snapshots available, which might be limited in many acoustical environments due to the propagation speed, large array aperture, and non-stationary field. This paper proposes a new approach for wideband source enumeration and direction-of-arrival (DOA) estimation on any sparse array geometry. The proposed algorithm decomposes the wideband signals into multiple disjoint frequency bands, computes the narrowband spatial periodograms and averages them to reinforce the sources’ spatial spectral information. The spatial correlation estimated from the wideband periodogram populates the diagonals of a Hermitian Toeplitz ACM. This ACM then goes through eigenvalue decomposition, where its eigenvalues are employed for source enumeration through a new information based criterion and its eigenvectors for DOA estimation through the MUSIC algorithm. Simulations show that the proposed algorithm achieves improved performance enumerating and estimating DOAs for more wideband sources than sensors in low snapshot scenarios when compared to existing approaches. [Work supported by ONR grant N00014-13-1-0230.]
Frequency-difference beamforming in inhomogeneous media
Authors: Douglass Alexander S. , Dowling David R.
Published: June 2017

Frequency-difference beamforming (Abadi et al., 2012, JASA, 132, 3018-3029) is an array signal processing technique that overcomes the limitations of the spatial Nyquist criterion by lowering the processing to out-of-band frequencies. This is accomplished using a quadratic product of complex signal amplitudes at different frequencies, resulting in wave propagation information at the out-of-band difference-frequency. Acoustic waves are susceptible to strong scattering in inhomogeneous media when the sizes of the inhomogeneities are comparable to or larger than the signal wavelength. Thus, conventional beamforming in random media at high frequencies with sparse arrays may be impossible, even in the presence of small inhomogeneities. However, at lower frequencies, acoustic propagation and beamforming in the same environment might not be significantly impacted. Thus, frequency-difference beamforming in the presence of high-frequency scattering is expected to maintain robustness similar to that of a low-frequency field. In this presentation, we present a theoretical framework that supports this hypothesis using the Born approximation. The theory is tested using experiments in a 1.07-m-diameter, 0.8-m-deep cylindrical water tank with an array of up to 16 receivers and 100 kHz to 200 kHz signal pulses that propagate through an inhomogeneous medium. [Sponsored by NAVSEA through the NEEC, and by ONR.]
An effective surface loss model for shallow water propagation and reverberation at mid-frequency that accounts for surface forward scattering
Authors: Thorsos Eric I. , Hefner Brian T.
Published: June 2017

A transport theory approach has been developed for modeling shallow water propagation and reverberation at mid-frequencies with emphasis at 1-3 kHz. With this approach, sea surface forward scattering can be taken into account in a 2-D (range-depth) approximation. The effects of surface forward scattering on reverberation level for typical conditions can be significant (>10 dB), even though bottom backscatter typically dominates reverberation in shallow water. However, effects of surface forward scattering have not been treatable with traditional ray-based codes, since it is implicit in these codes that the surface interaction is a specular reflection combined with some loss, and accounting for the change in grazing angle due to forward scattering, crucial for reverberation modeling, does not naturally come into it. A method to account for forward scattering with ray-based codes will be described. Transport theory results are used to develop an effective surface loss model. It is referred to as TOTLOS, for the surface loss for the total field, reflected plus scattered. While it is referred to as an effective surface loss model, the model can yield either loss or gain, depending on the grazing angle and other parameters of the environment. [Work supported by PMW-120 and ONR Code 322.]
Acoustic scattering from stainless steel shells with varying wall thickness using a biomimetic click: Modeling and interpretation
Authors: Qiao Gang , Qing Xin , Nie Donghu
Published: June 2017

Using broadband click pulse, dolphins can discriminate cylindrical shells with subtle difference in wall thickness. In this study, finite element models were built to calculate the acoustic scattering from stainless steel shells with varying wall thickness. In order to further analyze the mechanism of interaction between click pulse and shells, the scattering field in fluid and the stress distribution in solid were calculated by transient solver in time domain. The simulation results show that the acoustic solid interaction leads to object resonance, and then the elastic waves radiate into surrounding fluid. Furthermore, there are significant differences among the elastic waves from different shells with varying wall thickness. It suggested that the crucial information about shell’s wall thickness is hidden in elastic echo. The results show a promising way to further understand the target discrimination in dolphin’s biosonar.
Standards for processing and reporting metrics of underwater sound for use in risk assessment
Authors: Ainslie Michael A. , de Jong Christ A. , Halvorsen Michele B. , Ketten Darlene R. , Prior Mark K.
Published: June 2017

Anthropogenic underwater sounds create a potential risk to aquatic organisms. Many regulators require this risk to be assessed before allowing a sound-producing activity to proceed. Regulators typically set allowable exposure criteria for a range of acoustic parameters and require the assessment to address whether a given acoustic metric would exceed its specified threshold. While the value of the threshold is usually clear, the procedure required to calculate the metric is sometimes unspecified or described in insufficient detail, leading to ambiguity in interpretation. Processing and reporting procedures are described that enable intra- and inter-project consistency for processing and reporting of metrics. Quantities derived from sound pressure and sound particle motion are considered, resulting in metrics relevant to fish, aquatic invertebrates, and aquatic mammals. Specific metrics for which procedures are described include transient duration, zero-to-peak quantities, mean-square and time-integrated-squared quantities (e.g., sound exposure), and their spectral densities. The processing is relevant to ambient sound as well as sound from specified activities such as drilling, pile-driving, seismic imaging, or dynamic positioning. Specific issues addressed include the specification of one-third-octave bands, and the standardization of units and reference values used for reporting. [Work sponsored by the E&P Sound and Marine Life Joint Industry Programme.]
The noise of rock n’ roll: Incidental noise characterization of underwater rock placement
Authors: Portugal Rute , Cheong Sei-Him , Brocklehurst James , Evans Breanna
Published: June 2017

Underwater noise is a growing concern to conservation and stock management efforts to which supra-national organizations (e.g., OSPAR or the European Union) and governments (e.g., USA) are beginning to respond by building catalogues of the noise introduced in the marine environment by human activity. Rock placement is a construction activity for which there is scarcely any data available. In order to fill the knowledge gap, opportunistic recordings were taken while the Gardline Mk 3 hydrophone array was deployed for Passive Acoustic Monitoring and mitigation for marine mammals. The recordings were analyzed for their spectral and temporal characteristics, a correlation analysis between the amount of rock placed and the intensity of sound produced was made, and the suitability of the hydrophone array for the collection of this type of data was assessed.
Acoustic ground truthing of seismic noise in Chatham Rise, New Zealand
Authors: Cheong Sei-Him
Published: June 2017

Noise generated by seismic survey is widely recognised to have ecological consequences to marine ecosystem. Between the 31st January and 21st March 2016, a geophysical research survey was conducted in Chatham Rise, New Zealand to collect seismo-acoustic data using a Sercel seismic streamer in order to ground-truth the underwater noise impact assessment, conducted according to the DOC (NZ) Seismic Survey Code of Conduct. Data were analyzed to determine the received sound level at a distance up to 3 km from the source array. This paper establishes the method to predict the impact radii in order to validate the results obtained using Gardline 360M predictive model. The aim was to provide confidence to the capability of predictive modeling for estimating the impact zone of a seismic sound source. Data showed that multipath reflections can fluctuate significantly according to the seafloor topography; however, a very consistent trend can be obtained from direct propagation to confidently establish mitigation radii. Results show that the employment of a seismic streamer for the establishment of effective mitigation radii is technically feasible and maybe used as a tool to ground truth predictive modelling as part of mitigation plans to reduce the potential risk of acoustic trauma.
Environmentally adaptive acoustic sensing, communication, and navigation in distributed undersea networks
Authors: Schmidt Henrik
Published: June 2017

The explosive improvement in the capabilities of both hardware and software for unmanned underwater vehicles (UUV) is rapidly transforming the concept of operations for ocean science, exploration, surveillance and warfare. Thus, autonomous underwater vehicles, including autonomous gliders and propelled vehicles, are now standard tools on research vessels, cabled observatories and naval assets for environmental assessment on both local, regional and global scales. As was the case for manned undersea platforms, underwater acoustic s is critical to the operation of such systems, providing the only means for communicating information to, from and between undersea platform beyond a few tens of meters, and as such forms the basis for command and control, navigation, and remote sensing in the ocean. This in turn makes the operation of such systems highly sensitive to the acoustic environment with its convergence zones and extensive shadow regions, making it critical to robust operations to augment the network and platform control with an artificial intelligence framework which, using environmental acoustic modeling allows the network to autonomously adapt its configuration for optimal sensing, communication and navigation. Using the MOOS-IvP autonomy architecture, such a model-based environmental adaptation framework has been developed and demonstrated in simulation and in field deployments. [Work supported by ONR, DARPA, and Battelle.]
Near real-time passive acoustic detection and reporting of marine mammals from mobile autonomous platforms
Authors: Baumgartner Mark F. , Van Parijs Sofie M. , Hotchkin Cara F. , Ball Keenan , Partan Jim
Published: June 2017

Over the past two decades, passive acoustic monitoring has proven to be an effective means of estimating the occurrence of marine mammals. The vast majority of applications involve archival recordings from bottom-mounted instruments or towed hydrophones from moving ships; however, there is growing interest in assessing marine mammal occurrence from autonomous platforms, particularly in real time. The Woods Hole Oceanographic Institution has developed the capability to detect, classify, and remotely report in near real time the calls of marine mammals via passive acoustics from a variety of long-endurance autonomous platforms, including Slocum gliders, wave gliders, and moored buoys. The mobile Slocum and wave gliders provide marine mammal occurrence information in near real-time over spatial scales of hundreds to thousands of kilometers and temporal scales of a few months. Buoys and Slocum gliders are now being used regularly to accurately monitor baleen whales in near real-time off the east coasts of the U.S. and Canada. Our long-range goal is to incorporate this capability into regional and global ocean observatory initiatives to (1) improve marine mammal conservation and management and (2) study changes in marine mammal distribution over multi-annual time scales in response to climate change.
Transmission of side-scan sonar snippets from an underway unmanned underwater vehicle
Authors: Seto Mae L. , Danckaers Alice
Published: June 2017

An unique vector quantization compression methodology was applied to compress and encode side-scan sonar snippets of mine-like objects generated by automated target recognition tools on-board underway unmanned underwater vehicles (UUV). These compressed and encoded images were then further formed into acoustic packets. The objective was to transmit these acoustic packets, underwater, as representations of the sonar snippets (mugshots). The ability to transmit sonar snippets underwater while the UUV is underway is important as it allows the above-water operator to examine an image of mine-like objects, without recovering the UUV, for a timely decision on whether the object is actually a mine. This vector quantization method was used because of its terseness and thus it could be transmitted by WHOI underwater micromodems integrated on IVER3 UUVs. This presentation describes the algorithm, its implementation, and its initial in-water validation in local waters. This capability was also validated and demonstrated during the Royal Navy Unmanned Warrior 2016 exercise. Results from this will also be presented and discussed.
Modern enhancement systems substitute room acoustic design?
Authors: Ahnert Wolfgang , Behrens Tobias
Published: June 2017

The acoustic properties of halls and theatres are traditionally achieved by the acoustic design regarding primary shape and secondary structure of interior design. Until now acousticians regularly use their experience and additionally various tools for predicting the acoustic properties of the acoustic design: Physical scale model measurements and/or since the 1990 ties computer simulation as a standard method now. The acoustic properties are evaluated later subjectively by visitors and objectively by engineers with the means of specially developed measures. Parallel to this traditional approach electronic enhancement systems have been developed allowing e.g. a multipurpose hall to convert into a space for concert performances. Since the 1970 ties different systems with different technical approaches have been developed, and it could be said that today electronically generated acoustic properties in halls can be achieved in highest quality satisfying both musicians and audience. After a short overview of this development the pros and cons are discussed to use these electronic enhancement systems more and more which could lead to reduced efforts in traditionally achieved high-end room acoustic design. Limits to substitute room-acoustic design by enhancement systems are discussed finally.
Various applications of active field control (AFC)
Authors: Watanabe Takayuki , Miyazaki Hideo
Published: June 2017

AFC was developed as a tool for an acoustical design and has been improved to meet various types of requirements for acoustic consulting projects. The current system is the 7th generation which consists of a hybrid of the regenerative and non-regenerative systems. The system configuration is adjusted depending on the objectives for a venue. Two unique cases of AFC applications are discussed. (1) Compensation of acoustics in the auditoria without orchestra shells. The objectives of the system are (a) the enhancement of early reflections for performers, (b) the extension of the reverberation time and the enhancement of the sound energy on the stage, and (c) the enhancement of early reflections in the audience area. This system showed an improvement of about 1 to 2 dB in STearly and more than 2 dB in G in the audience area, which is equivalent or better performance than simple mobile type orchestra shell. 2) Improvement of the acoustics under the balcony in the auditoria. The system is based on a non-regenerative system which recreates the sound field above the balcony area by using measured impulse responses. The result of the subjective experiments shows that the effectiveness of the system is significant.
Object based approach for electronic variable acoustics systems
Authors: Frutos-Bonilla Javier , Brix Sandra , Sladeczek Christoph , Rodigast Rene , van Munster Bjorn
Published: June 2017

Demand for spatially accurate high-quality sound reproduction in the audio entertainment industry is now at an entirely new level. In today’s world of immersive entertainment, sound reproduction is about more than just decibels—via the accurate localization of sound sources, performances can be immeasurably enhanced in classical concerts, operas, theatres, and every field of live entertainment. The days of two-dimensional PAs are over—a new era has arrived with 3D spatial sound and enhanced room acoustics. This paper describes a fully object-based approach to immersive sound reproduction, combining 3D positioning of audio sources and acoustic enhancement on the same unit by processing room reflections as audio objects. The algorithms combine the flexibility of traditional in-line digital reverberation devices with the quality and natural impression of a regenerative reverberation. The result of this process is a subset of discrete, early and late reverberant reflections which are convolved with the direct sound to serve as input objects for further processing. This unique object based system approach offers many advantages with respect to the traditional channel based approach. The technological principles of this approach, along with the results of successful applications throughout Europe, will be shown.