bluuebunny/crossref_metadata_2025 huggingface dataset:
Rayleigh wave method of measuring the frequency-dependent shear modulus
Authors: Muller Marius J. , Mongeau Luc
Published: June 2017

The viscoelastic characterization of biomaterials is needed to develop compatible injectable implants for versatile medical applications. The present study is an investigation of injectable hydrogels for use in healing scarred soft tissues. A Rayleigh wave method was used to measure the frequency-dependent shear modulus of viscoelastic materials. A block of synthetic material was cast and excited by a shaker over a wide frequency range. The transverse velocity of the surface was recorded via an accelerometer and Laser Doppler Vibrometry (LDV). The linear phase delay validated the use of a transfer function method. The complex elastic modulus and the loss factor were obtained from the measured wave speed, and compared to data from a torsional rheometer. The benefits of the wave propagation approach compared to conventional parallel plate rheometry are that the material properties are acquired over a greater bandwidth. There is also a possibility of applying the same technique in vivo and in cell-seeded materials.
Effect of microannulus on ultrasonic pulse-echo resonance, flexural, and extensional Lamb-wave cement-evaluation measurements
Authors: Klieber Christoph , Brill Thilo
Published: June 2017

Subterranean wells are usually constructed by cementing steel tubes, called casings, inside the borehole. The cement quality is typically verified through ultrasonic measurements deployed from inside the casing. Environmental effects such as cement shrinkage or changes in static pressure can alter the bonding properties between casing and cement with significant effects on the acoustic measurement response. The cement may detach from the casing, opening a gap, called a microannulus. This microannulus is sized from submicrometer to hundreds of micrometers and filled with either gas or liquid. The subwavelength nature of the microannuli does not allow a direct, unambiguous characterization through an ultrasonic measurement. We studied the measurement signature of ultrasonic-pulse-echo resonance, and flexural and extensional Lamb waves for air- and liquid-filled microannuli for various annulus materials and steel-casing thicknesses. This characterization allows statistically linking measured results to microannulus widths. The highest-precision measurements used in-situ laser interferometry through transparent annulus samples to characterize the microannulus thickness.
A simplified compression test for the estimation of the Poisson’s ratio of viscoelastic foams
Authors: Bonfiglio Paolo , Pompoli Francesco
Published: June 2017

The present paper describes a simplified procedure for determining the Poisson’s ratio of homogeneous and isotropic viscoelastic materials. To that end, a cylindrical shaped material is axially excited by an electromagnetic shaker and displacement waves are investigated. Using a frequency sweep as an excitation signal, the frequency domain displacement response is measured upstream and sideways of the sample itself and, by using a plane cross section analytical model of the experimental setup, the Poisson’s ratio is estimated using a minimization based procedure applied on radial displacement once the complex modulus has been directly determined under the assumption of spring-like behavior of the axial displacement. The results are presented and discussed for different materials and compared with well-established quasi-static and finite element simulations.
Characterization of natural and recoil-induced vibration of an AR-15 rifle at the cheekbone-stock interface
Authors: Cyders Timothy J. , DiGiovanni Jeffrey J. , Wilhelm Jay
Published: June 2017

Effects of sound pressure and shock on hearing loss have been widely studied. Studies involving direct assessment of sound pressure levels and influencing variables related to rifle discharge, especially with respect to standard military small arms have mostly focused on the effects of external pressure on hearing. Other studies have characterized physiological effects of external vibration on animals and humans. Shock phenomena and high-pressure waves have been linked to effects from gradual changes in tissue thickness to traumatic brain injury and other central nervous system maladies. Rifle shooters, including soldiers, law enforcement officers, and hunters, typically shoulder rifle-type firearms in a way that puts the buttstock in direct contact with the cheekbone, known as the “cheek weld.” This work experimentally characterizes the vibrations experienced by the shooter at the cheek/buttstock interface, and discusses expected physiological and acoustical effects as a result of conduction into the skull.
Vibration control with a bistale nonlinear absorber
Authors: Iurasov Volodymyr , Mattei Pierre-Olivier
Published: June 2017

The goal of our research is to develop a nonlinear absorber that will be effective at low frequencies and low amplitudes of vibration, notably in the domain of vibroacoustics. From this perspective, the usual Nonlinear Energy Sinks (NESs) based on the idea of the internal resonance have certain limitations due to the relatively high activation threshold. In order to decrease this threshold we developed the idea of a bistable absorber. The bistability provides a chaotic regime in the absorber dynamics that leads to effective dissipation by the NES. While this energy transfer is completely different from the well-known energy pumping, the two types share the main features such as the activation threshold and the functioning region. The bistable NES that we propose consists of a clamped-clamped buckled beam and an attached mass. The experimental and numerical tests performed for our particular realization of a bistable absorber have shown its high efficiency and robustness.
Physical implementation of immersive boundary conditions in one dimension
Authors: Becker Theodor S. , van Manen Dirk-Jan , Donahue Carly , Robertsson Johan O.
Published: June 2017

Immersive boundary conditions (IBCs) are a novel approach to target-oriented numerical wavefield modeling. When implemented physically, IBCs allow the construction of anechoic chambers that actively suppress the reflection of wavefields from the boundaries of a physical domain, such as a wave propagation laboratory. Moreover, IBCs can be used for immersive wave propagation experimentation by linking the wave propagation in the physical domain with the propagation in a virtual domain enclosing the physical domain. In this case, the IBCs correctly account for all wavefield interactions between the two domains. The physical implementation of IBCs is achieved by densely populating the boundary surrounding the physical domain with transducers that enforce the necessary boundary conditions. To estimate the signals that need to be emitted at the injection boundary, a second surface of transducers slightly inside the physical domain records the propagating wavefield. The recorded wavefield is extrapolated to the injection boundary by evaluating a Kirchhoff-Helmholtz integral in real-time using an FPGA-enabled data acquisition and control system. A recently constructed one-dimensional acoustic wave propagation laboratory provides an ideal setup for the physical installation of IBCs in one dimension. In this work, we demonstrate the implementation of IBCs on one side of this laboratory.
Improvement of acoustic and vibration models by temporal error metrics
Authors: Liem Alyssa T. , McDaniel James G.
Published: June 2017

Analyses and examples are presented that explore the limits and accuracies of a technique for improving acoustic and vibration models by temporal comparisons to experimental data. In a previous presentation, the authors proposed the use of impulsive excitations followed by time windowing of responses. This approach allows comparisons between experimental data and model predictions over an isolated spatial region whose volume is a fraction of the entire system volume. The advantage of this spatial isolation is that it significantly reduces the number of model parameters that must be varied to bring the model predictions into agreement with the experimental data. In the present work, the method is analyzed in detail to quantify the limits and accuracies of the method relative to window size, number of measurement locations, and excitation. Two types of examples will be presented to illustrate these findings. The first involves the improvement of material properties for a homogeneous region. The second involves the improvement of the coupling conditions between two homogeneous regions. Results of these examples will be reviewed in the context of existing and emerging measurement technologies, such as digital image correlation.
Validation of a hybrid boundary and finite element method for the simulation of large membrane-based piezoelectric transducer arrays in immersion
Authors: Shieh Bernard , Sabra Karim G. , Degertekin F. Levent
Published: June 2017

Membrane-based piezoelectric ultrasonic transducers, especially piezoelectric micromachined ultrasonic transducers (PMUTs), are a promising technology for the realization of large transducer arrays for use in integrated imaging, sensing, and actuation where a broadband response is desirable. In this work, a hybrid boundary and finite element method is proposed for the transmit simulation of large PMUT arrays in immersion. Finite element software (COMSOL) readily handles the simulation of single membrane structures, from which static deformation (stiffness) and harmonic displacement data is extracted. A boundary element formulation based on these inputs handles the membrane-to-membrane acoustic cross-coupling through the calculation of a mutual impedance matrix. For arrays consisting of hundreds of membranes or more, the problem of quadratic storage and cubic time complexity for boundary element is avoided by employing a multi-level fast multipole algorithm (Shieh et al., IEEE Trans. UFFC, 63, 1967-1979). We validate this hybrid method for common membrane geometries, including square and circular membranes with varying degrees of electrode coverage.
Two methods of ship structure health monitoring sample expansion: A comparison study
Authors: zhang linke , Li Hejun , Tan You
Published: June 2017

The fault diagnosis of ship structure-borne sound transfer path is mainly based on data binary classification, which requires enough transfer functions or training samples. Actually, the data collection sensors installed on the ship are always limited resulting in quite lack of real training samples. Hence, it is of great significance to solve such a small sample problem for the ship structure acoustic fault identification and location. In this paper, some theoretical studies have been conducted to compare two methods of structure acoustic fault sample expansion including extracting the local Green’s function from cross-correlations of ambient vibration and dynamic monitoring based on the transmissibility function. Then a novel model of fault sample expansion was put forward and verified through a simulation example. The research shows that the proposed two methods have their respective pros and cons. Some suggestions on how to employ these two methods to ship structure health monitoring were also proposed.
Detection of structural bolt detorquing using direct acoustic measurement
Authors: Guarino Joe , Hamilton Robert
Published: June 2017

A method for detecting loosened bolts in a structural joint based upon open-loop acoustic measurement is presented. The acoustic measurement is taken direclty on the bolt head. The response of the bolt to a proximal hammer impact is evaluated and characterised using wavelet decomposition of the signal measured from the bolt head. Results are presented from a set of structural bolts in several conditions of preload and looseness. The study could enable a quick and simple method for detecting and evaluating detorqued bolts in structural joints.
Fricative and affricate productions of Mandarin-speaking children with cerebral palsy: A view from spectral moment analysis
Authors: Liu Chin-Ting Jimbo , Chen Li-mei , Hustad Katherine C. , Kent Ray D. , Wang Wan-Chen , Li Hsin-yu
Published: June 2017

Spectral moment analysis has been adopted as a means of quantifying the differences in the place of articulation among fricatives and affricates produced by typically developing populations and individuals with language disorders in Mandarin Chinese (Jiang, Whitehill, McPherson & Ng, 2015, 2016; Lee, Zhang & Li, 2014). Therefore, this study intends to examine the fricative/affricate productions in Mandarin Chinese between typically developing children (TDs) and cerebral palsy children (CPs) with dysarthria by focusing on the spectral moment analysis (i.e. M1: mean, M2: standard deviation, M3: skewness and M4: kurtosis). Results from nine CPs (Mean:7;0) and ten TDs (Mean: 5;7) indicated that: 1) The average M2 values of all fricatives and affricates were significantly higher among CPs; 2) For individual segments, the M2 values of voiceless alveolo-palatal fricatives, aspirated/unaspirated voiceless dental affricates and the M3 values of voiceless velar fricatives from CPs were significantly higher than those from TDs. Based on the articulatory interpretations of the spectral moment analysis (Li, Edwards & Beckman., 2009; Li, 2012), it was concluded that CPs tended to have a more anterior place of articulation for certain fricatives and affricates. Future cross-linguistic studies might help identify if current observations are language-specific or universal.
Protophone codings for early speech development of infants with high risk of cerebral palsy in the first year of life
Authors: Wang Wan Chen , Chen Li-mei , Lin Yung-Chieh , Chen Li-Wen
Published: June 2017

Protophones (Oller, 2000) are regarded as precursors of the human speech. Deviation in the onset of the protophone patterns is associated with a variety of developmental disorders. This study investigated early speech development of three infants with high risk of cerebral palsy (CP) in the first year of life based on 6 categories of protophones: vocant, growl, squeal, cry, laugh, and others (including whisper, ingressive sound, raspberry, other consonant alone, and yell) (Buder et al., 2012). They were early identified with high risk of CP and had been detected disorders by pediatricians. Three recordings in the period of 4 to 12 months from each infant were perceptually categoriezed. The major findings were (1) The frequency of vocant increased over time; (2) others dominated in the vocalizations; (3) squeal (high pitch) show lower frequency than growl (low pitch). These preliminary findings displayed a profile of early vocalization of children with CP. In future studies, data from typically developing children should also be included to reveal the deviation of disordered speech. Moreover, more data from more participants should be included to trace how these six categories of protophones are variegated in the first year of life, and then develop toward mature speech categories.
Identification of the spectrotemporal modulations that support speech intelligibility in hearing-impaired and normal-hearing listeners
Authors: Venezia Jonathan , Martin Allison-Graham , Richards Virginia
Published: June 2017

Accurate encoding of the spectrotemporal envelope of speech is essential for intelligible perception. We have recently developed a psychophysical procedure that identifies the relative contributions of particular spectrotemporal modulations (STMs) to intelligibility. Here, we use the procedure to test the hypothesis that intelligibility is supported by different patterns of STMs in hearing-impaired versus normal-hearing listeners. A group of 20 hearing-impaired listeners and an age-matched group of 13 normal-hearing (≤ 25 dB HL from 0.25-4 kHz) listeners performed a speech recognition task in which acoustically-degraded sentences presented over headphones were repeated back verbally and scored for keywords correctly identified. Different patterns of STMs were removed on each trial by applying a randomly-shaped filter to the 2-D modulation power spectrum. Reverse correlation was used to identify STMs that predicted performance (i.e., intelligibility) across trials. Three main findings describe the results: (1) the group-average patterns of STMs supporting intelligibility did not differ between hearing-impaired and normal-hearing listeners; (2) greater individual variability in STM patterns was observed within the hearing-impaired group; and (3) hearing-impaired listeners required more overall STM information to perform the task. The results suggest hearing-impaired listeners rely on the same STM information as normal-hearing listeners but encode this information less efficiently.
Automated anaysis of syllable complexity in children as an indicator of speech disorder
Authors: Speights Marisha , Boyce Suzanne E. , MacAuslan Joel , Silbert Noah H.
Published: June 2017

Speech disorders affecting intelligibility commonly occur in young children. One way to differentiate normal versus delayed speech development is to measure the ability to articulate increasingly complex syllables. We present a computer-assisted approach, Syllabic Cluster Analysis (SCA) as an objective measure of syllabic complexity. SCA uses clusters of acoustic landmarks to detect articulatory complexity in the production of syllables. Although most research using landmarks focuses on the lexical content of speech, SCA focuses on non-lexical differences which is well suited for analysis of speech with decreased intelligibility. Feasibility of this system to predict disordered speaker group is tested. Words recorded by normal adult (n = 10) and typical child (n = 20) speakers and children with speech disorders (n = 10) were ranked using a published word complexity measure to establish a high complexity word list (n= 20). Multinomial logistic regression models are fit for Landmarks per Syllabic Cluster (LM/SC) and Syllabic Cluster per Utterance (SC/UTTs) counts as speech complexity predictors. LM/SC counts are a significant predictor of disordered status in the model when measuring a short set of complex words (p <.001). Future work toward the development of automated diagnostic tools is discussed.
Acoustic cues to distinctive features are modified in the speech of typically-developing versus atypically developing children
Authors: Talkar Tanya , Zuk Jennifer , Guerrero Maria X. , Choi Jeung-Yoon , Shattuck-Hufnagel Stefanie
Published: June 2017

Non-word repetition tasks have been used to diagnose children with various developmental difficulties with phonology, but these productions have not been phonetically analyzed to reveal the nature of the modifications produced by children diagnosed with SLI, autism spectrum disorder or dyslexia compared to those produced by typically-developing children. In this study, we compared the modification of predicted acoustic cues to distinctive features of manner, place and voicing for just under 30 children (ages 5-12), for the CN-Rep word inventory, in an extension of the earlier analysis in Levy et al. 2014. Feature cues, including abrupt acoustic landmarks (Stevens 2002) and other acoustic feature cues, were hand-labeled and analysis of factors that may influence feature cue modifications included position in the word, position in the syllable, word length measured in syllables, lexical stress, and manner type. Results suggest specific patterns of modification in specific contexts for specific clinical populations. These findings set the foundation for understanding how phonetic variation in speech arises in both typical and clinical populations, and for using this knowledge to develop tools to aid in more accurate and insightful diagnosis as well as improved intervention methods.
Automated screening for speech disorders using acoustic landmark detection
Authors: Speights Marisha , Ishikawa Keiko , Boyce Suzanne E. , MacAuslan Joel
Published: June 2017

Most children effortlessly learn how to coordinate movements for normal speech production. About one in twelve preschool-aged children, however, show delays in speech production capability that may put them at risk for academic and behavioral difficulties, if not identified and treated. Automated tools that can distinguish between children with and without speech and language impairments could serve as a useful clinical tool for early identification of speech related disorders in young children. In this study, we consider measures based on detecting sequences of acoustic landmarks characteristic of normal speech production over multisyllabic words and continuous speech samples. Ten normal adults, ten typical children and ten with speech disorders recorded twenty multisyllabic words and thirty-three sentences. Acoustic landmarks patterns within utterances and syllabic clusters are examined to characterize differences in landmark sequences between normal and disordered speech. Shannon’s Entropy and ROC analysis are used to evaluate the landmark patterns as potential diagnostic measures of a-typical speech production. We discuss these results and our future work toward developing a fully automated clinical screening tool.
Nasality patterns in word productions of children with cochlear implants: Evidence from Greek
Authors: Okalidou Areti , Koenig Laura L. , Psillas George
Published: June 2017

Typical speech production development requires adequate auditory input. Children who are born deaf or become deaf in early childhood display atypical speech patterns, especially for articulatory actions that cannot be seen. Such actions include tongue backing, laryngeal actions, and velar function. Several previous authors have discussed how inadequate auditory input affects anterior-posterior tongue positioning and laryngeal parameters, compromising phonetic contrasts (e.g., vowel and voicing distinctions), but few studies have directly assessed velar control in hearing-impaired children. This work presents nasometer data for Greek-learning children with cochlear implants [CI] and age- and sex-matched normal hearing [NH] controls, ages 5-16 years. Participants produced single words, elicited in response to visual and auditory prompts. Bisyllabic word types of varying stress pattern were contrasted in nasality and position of the target consonant. Based on the two nasometer microphone signals (oral and nasal), word and segment boundaries were defined, and nasometer values over these intervals were extracted. We will present whole-word data, comparing nasalance values between NH and CI children, and examples showing atypical oral-nasal timing in the CI population. This preliminary analysis shows some of the ways in which hearing-impaired children with cochlear implants may show unusual patterns of velar control.
Predicting intelligibility of dysphonic speech with automatic measurement of vowel related parameters
Authors: Ishikawa Keiko , Meyer Meredith , MacAuslan Joel , Boyce Suzanne E.
Published: June 2017

Speakers with dysphonia frequently report difficulty with being understood in noisy places. Perception of vowels plays an important role in intelligibility. Dysphonic speech is typically characterized both by shorter periodic intervals and an increased proportion of noise vs. harmonic components, potentially obscuring acoustic cues for identification of vowels. This study examined whether vowel-related acoustic measures would predict intelligibility of dysphonic speech. Sentences from the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) were recorded from 18 dysphonic speakers (6 adult females, 6 adult males, and 6 children) and 3 normal speakers (1 adult female, 1 adult male, and 1 child). These sentences were analyzed acoustically by SpeechMark® Wavesurfer plug-in version, a speech analysis tool based on the landmark theory of speech perception. The sentences were presented to 45 listeners for perceptual rating of intelligibility at 3 S/N ratios. The following output parameters were compared: vowel space area, number of vowels whose F1 and F2 values fell within a standard vowel quadrilateral (defined based on existing literature), and number of vowels with normal formant bandwidth. Preliminary results indicated that number of vowels with normal formant bandwidth falling within the quadrilateral significantly predicted the intelligibility ratings of dysphonic speech at all noise levels.
An optimized lumped model for tracheoesophageal speakers
Authors: Zanotelli Guilherme , da Silva Andrey R.
Published: June 2017

Since the advent of the first lumped model of the phonatory system by Flanagan and Landgraf (1968), many improvements have been made in order to capture more realistic features of the human phonation in glottal speakers. Although lumped models are quite limited when it comes to representing realistic structural and fluid dynamic aspects, they are very important to understand fundamental features of human phonation. Nevertheless, only a few lumped models have been proposed in order to investigate the dynamics of the pharyngoesophageal segment in tracheoesophageal speakers. This work presents some improvements on a lumped model of the pharyngoesophageal segment, firstly proposed by Schwarz et al. (2011). The improvements have been achieved by conducting an optimization process that involves the glottal volume flow as the optimization function, using as reference the experimental data obtained from tracheoesophageal speakers. The results suggest that the lumped model of the esophageal region can be extended to capture important features, such as the pressure threshold for the onset of self-sustained oscillation.
Effectiveness of an intervention program combining direct vocabulary instruction and individualized phonetic training for Mandarin-speaking young children with specific language impairment
Authors: Chen Yuchun
Published: June 2017

Children with specific language impairment (SLI) demonstrate deficits in vocabulary development and novel word learning process, which have been proposed to stem from their speech perception and phonological processing deficits. In this study, we designed an intervention program combining small-group direct vocabulary instruction and individualized phonetic training computer program. Twenty-five 5- to 7-year-old children with SLI participated in the study, and another 15 children with SLI served as control group. All participants in the experimental group attended 50-minutes direct vocabulary instruction class with interactive activities for ten weeks. The phonetic training computer games included AX discrimination and identification tasks of Mandarin consonant and lexical tones minimal pairs presented in single word and sentence levels. Children were asked to play the phonetic training games at least 30 minutes a week at home and encouraged to run more if they prefer. Results showed that children in the experimental group performed better than control group in the post test, including receptive and expressive vocabulary knowledge. In addition, there was a correlation between the gain in the post test and the time spent in the phonetic training game. The result suggests the vocabulary intervention programs incorporated with speech perception training promote children’s vocabulary abilities.
Vowel contrasts relative to schwa across tasks: Preliminary findings for Parkinson’s disease
Authors: Kuo Christina
Published: June 2017

The purpose of this study is to quantify acoustic contrasts of vowels in relation to the mid-central unrounded vowel schwa produced by speakers with Parkinson’s disease (PD) in different speaking tasks. The study is motivated by a hypothesis that schwa may serve as a speaker-specific reference for vowel contrasts given its associated anatomical properties of a neutral vocal tract. For the present study, a speaker-specific reference schwa is identified from averaged first and second formant (F1 and F2) frequencies of unstressed article “a” productions in citation form. Two questions are addressed. First, can speaking-task related changes in vowel contrasts be expressed by vowel-schwa distances in the acoustic space consistently across speakers? Second, do characteristics of schwa-referenced vowel contrasts differ for speakers with PD and healthy speakers? F1 and F2 frequencies of schwa and vowels /i/, /a/, and /u/ in three tasks including clear-speech, sentence reading, and passage reading are examined. The Euclidean distance between each vowel and schwa is evaluated for a given speaker across tasks. It is hypothesized that the within-speaker distances between vowels and schwa are task-sensitive in the direction of clear-speech to passage reading. Preliminary findings will be discussed within the framework of the acoustic theory and the Hyper- and Hypo-speech theory.
Comparison of thumb-pressure vs. electromyographic modes of frequency modulation for electrolaryngeal speech
Authors: Nagle Kathleen , Heaton James T.
Published: June 2017

Speaking with natural prosodic patterns is tremendously challenging when using an electrolarynx (EL). Some ELs enable dynamic fundamental frequency (f0) variation to provide prosodic patterns and thereby improve speech naturalness. This study compares EL speech produced using thumb-pressure f0 variation (TruTone™ EL) versus an experimental method wherein f0 variation is derived from submental (under chin) electromyographic (EMG) signals (EMG-EL). Eighteen Laryngectomees provided sentence-length samples of speech using these two EL devices, and measures of f0 mean, SD and range were made. The f0 coefficient of variation (f0CV; SD f0/mean f0) was also calculated as a measure of f0 variation relative to the mean (Cartei et al., 2012). Paired t-tests of f0 measures were used to compare EL devices within participants. Mean f0 range was significantly greater for the EMG-EL device than thumb-pressure EL device (16 of 18 speakers; p <.05). Although mean f0 was roughly the same across devices, f0CV was significantly higher for the EMG-EL than thumb-button EL (17 of 18 speakers; p<.05). The EMG-EL device enabled greater f0 variation than a thumb-pressure-controlled device, which is consistent with our prior findings that the EMG-EL supports more natural-sounding speech—even for EL users who own the thumb-pressure device.
Multi-frequency sparse Bayesian learning for matched field processing
Authors: Gemba Kay L. , Nannuru Santosh , Gerstoft Peter , Hodgkiss William S.
Published: June 2017

Compressive sensing has been applied to underwater acoustic problems. Using multi-frequency sparse Bayesian learning (SBL), we present simulation and data results (SWellEx-96 Event S5) including mismatch. Mismatch is defined as a misalignment between the actual source field observed at the array and the modeled replica vector. Results for a multiple-source scenario indicate that SBL outperforms WNC and MUSIC when localizing a quiet source in the presence of a stronger source. Furthermore, simulations (including snapshots not corresponding exactly to replicas) and data results demonstrate that SBL offers robustness to mismatch including array-tilt. The array-tilt mismatch in the data varies over time and is especially pronounced at the closest point of approach, being 2 degrees. Because of its computational efficiency and performance, SBL is practical for real time applications requiring an adaptive and robust processor.
An international standard for the measurement of underwater sound radiated from marine pile-driving
Authors: Robinson Stephen P.
Published: June 2017

The pile-driving of marine foundations radiates substantial levels of low-frequency impulsive noise into the water column, which can propagate over large distances. Concern over the potential for impact on marine fauna often results in a regulatory requirement to measure the radiated noise level over distances which may extend to tens of kilometres. Furthermore, if the transmission loss is to be established or validated it is necessary to measure as a function of range from the pile at a number of positions and, because of the variation in acoustic output during the pile-driving, particularly if a soft-start is employed, it is desirable to perform the measurement at a fixed range for the duration of the pile-driving operation. The noise generation mechanisms are complex, and a number of factors influence the noise radiated into the water column, including the water depth (exposing a different amount of the surface area of the pile), the seabed properties, and the penetration depth into the seabed by the pile, the pile dimensions, and the hammer energy. A standard method for the measurement of underwater radiated sound from percussive pile driving has been developed and is described here. The method includes a combination of fixed-range recordings and range-dependent hydrophone deployments. The method was established by Working Group 3 of Technical Committee 43 (Sub-Committee 3) of the International Organization for Standardization (ISO), and is published in 2017 as ISO 18406.
Underwater noise assessment for energy extraction and production systems using unmanned arial vehicles (UAVs)
Authors: Lepper Paul A. , LLoyd Steven , Pomeroy Simon
Published: June 2017

Traditional operations such as oil and gas exploration and production have long undergone sound field and environmental impact assessments of underwater acoustic noise. More recently emerging industries such as renewables (wind, wave, and tidal energy production) have also required scrutiny in terms of underwater noise sound fields. To make these assessments, sound fields are typically measured using hydrophones deployed from boats, drifting systems or moored acoustic data loggers. These measurements are often complex and expensive requiring complicated equipment deployments, boat operations and personnel in often-dangerous or hazardous environments. Unmanned Ariel Vehicles (UAV) or drone based technologies offer the opportunity for rapid deployment of smart hydrophone systems arrays over a large spatial area with significantly lower operator and boat interaction improving deployment flexibility, cost and minimising safety concerns for boat based deployments. Results presented are from tests of a prototype multi-rotor system in an open water site, capable of flying to site, landing on the water, deploying a wideband hydrophone for underwater noise assessment and then returning to base. These developments and trials have demonstrated the overall feasibility of wide-scale rapid hydrophone deployment using UAV based sensors and its potential application to underwater sound field assessment across a variety of industries.
Explosive offshore structure removal noise measurements
Authors: Frankel Adam S. , Barkaszi Mary , Martin Jeffrey , Poe William , Giard Jennifer , Hunter Ken
Published: June 2017

The underwater structures that support wind turbines and oil drilling rigs must eventually be removed. Explosive severing is a commonly used removal method in which charges are inserted into a pile and placed below the seafloor to sever the pile. The open-water source level of an explosive charge is readily determined from its composition and weight (Urick 1986). However, the sediment and pile absorb much of the explosion’s energy. A recent study (BSEE project M13PX00068) measured explosive removals in the Gulf of Mexico. Peak pressure, impulse and energy flux density metrics were measured with a 12-element, two-dimensional array spanning 90 ft vertically and at distances out to 200 ft. Peak amplitudes, compared with theoretical open-water predictions, were reduced from 76% (75 lb charges) to 54% (200 lb charges). Measured results were also compared to predictions from the UnderwaterCalculator (Dzwilewski and Fenton 2003) that included pile and sediment attenuation effects. It accurately predicted the propagation from the current study and somewhat overestimated propagation for earlier data collected in shallower water with smaller charges. These data suggest that the model can be improved. Nevertheless the model is further validated for its primary purpose of estimating ranges to designated safety thresholds.
Constellation: A hybrid active accoustic system
Authors: Schwenke Roger W. , Parker Melody
Published: June 2017

Constellation is a hybrid active acoustic system that has been used in rooms ranging in size from a virtual reality cave to a sports arena. Constellation has been shown to control both the effective absorption of a room as well as the effective cubic volume. This paper will review how early reflections, effective absorption, and effective cubic volume have been controlled in rooms of various sizes. Recently, there has been a trend of larger classical ensembles performing in smaller venues. If the strength of the room is held constant, but the cubic volume is cut in half, the reverberation time is also cut in half. If a room has exclusively physical acoustics, it is impossible to replicate both the strength and reverberation time of a symphony hall in a space that is considerably smaller (such as a rehearsal room). A special emphasis will be made on how Constellation is uniquely suited to address this challenge.
Carmen and Carmencita electroacoustic systems
Authors: Jagla Jan , Chervin Paul , Martin Jacques
Published: June 2017

During the last 20 years, CSTB successfully installed many Carmen systems in prestigious venues requiring variable acoustics all around Europe. Electroacoustic systems like Carmen turn a performance hall with naturally dry acoustics into a multipurpose venue that can host any type of performance from theatre to symphonic music. Carmen is based on the virtual wall principle, meaning that it simply changes the perceived absorption of walls and ceilings and their perceived distance to the receiver by placing Carmen cells on them. This principle enhances the natural acoustics of the hall without introducing any kind of electronic reverberation. Due to the large number of Carmen cells (typically over 30) required to homogeneously enhance a hall reverberation time, Carmen is not suited to small venues (under 700 seats). Also, it is well known that the main limitation of assisted reverberation systems is their significant price. Therefore, CSTB developed a new system called Carmencita using much less cells (8 to 16) and introducing a specific reverberation matrix to provide to small venues a large panel of acoustic presets. Moreover, to meet the growing demand of spatially diffused sound effects for theatre and contemporary dance, Carmencita also features new real time spatial diffusion algorithms.
Crosstalk cancellation using multiple synthesis sources
Authors: Hartmann William M. , Tropiano Anthony J.
Published: June 2017

The technique of crosstalk cancellation uses two synthesis loudspeakers in an attempt to produce well separated signals in a listener's ear canals. A variation on the technique can be applied in precise psychoacoustical experiments by using probe tubes in the ear canals throughout the presentation. The probe-tube application exhibits remarkable immunity to amplitude and phase variations in the responses of all transducers because the same system is used for presentation and for initial calibration. The self-correcting nature of the method even confers immunity to variations in the depth of the probe tubes within the ear canals. Because the solution to the 2-ear-2-speaker problem involves the inverse of a 2x2 matrix, the solution can become unstable, leading to pathologically large amplitudes. This problem can be almost entirely alleviated by using more than two synthesis speakers, and solving the resulting underdetermined inverse problem through the Moore-Penrose pseudoinverse. Random perturbation calculations show that using three or four synthesis speakers also reduces the ear-canal amplitude and phase sensitivity to inadvertent listener movements. However, more realistic calculations for inadvertent head-rotations indicate an additional important role for synthesis speaker location. [Work supported by the AFOSR.]
Considerations regarding the equalization for spatial playback from spherical microphone array recordings
Authors: Meyer Jens , Elko Gary W. , Backer Steven
Published: June 2017

The encoding of spatial sound fields captured by spherical microphone arrays into Eigenbeams (HOA signals) provides a compact representation of the sound field that facilitates spatially realistic audio playback in Higher-Order Ambisonics (HOA) applications. For spatial audio reproduction, a typical Ambisonics decoder generates the loudspeaker signals from the HOA signals by applying only simple scalar weights. However, since the HOA signals derived from physical microphone arrays are frequency dependent, such a frequency independent scalar weighting scheme will not result in the desired loudspeaker sound field reproduction. An analysis of this frequency dependency and some equalization schemes to mitigate detrimental effects resulting from frequency independent loudspeaker decoding will be discussed.
Spatial perception in binaural reproduction with sparse head-related transfer function measurement grids
Authors: Ben-Hur Zamir , Alon David L. , Hillis James , Rafaely Boaz , Mehra Ravish
Published: June 2017

Growing interest in virtual reality has led to greater demand for immersive virtual audio systems. High fidelity spatial audio requires individualized head related transfer functions (HRTFs). Individualized HRTFs are, however, typically unavailable as they require specialized equipment and a large number of measurements. This motivates the development of a simpler more accessible HRTF estimation process. Previous work has demonstrated that spherical-harmonics (SH) can be used to reconstruct the HRTF from a smaller number of sample points, but this method has two known types of error: spatial aliasing and truncation error. Aliasing refer to loss of ability to represent high frequencies. Truncation error refer to the fact the SH representation will be order-limited which further limits spatial resolution. In this paper, the effect of sparse measurement grids on the reproduced binaural signal is studied by analyzing both types of errors. The expected effect of these errors on the perceived location, externalization and source width, is studied using a theoretical model and an experimental investigation. Preliminary results indicate relatively large effects of SH order on sound localization and smaller effects due to aliasing errors.
Omnidirectional measurement of room impulse response using a small bookshelf loudspeaker as a sound source
Authors: Hidaka Takayuki , Koyanagi Shin-ichiro
Published: June 2017

A dodecahedral loudspeaker is commonly used in room acoustical measurements as an omnidirectional sound source. However, inverse filtering to obtain an ideal room impulse response (RIR) is not easy because of its irregular frequency and temporal characteristics. When this RIR is convolved with music signals, the reproduced sound does not possess adequate fidelity to evaluate the acoustical quality of the concert hall. Hence a new measurement method of the RIR by an omnidirectional source is proposed: RIR’s are measured by a small bookshelf loudspeaker rotating around its acoustic center in multiple directions, and the RIR’s are averaged to obtain omnidirectional response. Physical characteristics of the RIR determined with this procedure are given and the room acoustical parameters are compared with those by the dodecahedral method. Finally, application to subjective experiments is described.
A new multifrequency acoustic method for the discrimination of biotic components in pelagic ecosystems: Application in a high diversity tropical ecosystem off Northeast Brazil
Authors: Vargas Gary , Frédou Flavia , Roudaut Gildas , Lebourges-Dhaussy Anne , Habasque Jérémie , Bertrand Arnaud
Published: June 2017

Underwater acoustics have an unrealized potential for multicomponent ecosystem characterization. Various methods are used for multifrequency classification. To improve scatter discrimination we propose a new method based on the distribution of scatters on multifrequency spatial planes. Groups of scatters are defined a priori (from in situ sampling). Then we apply a sensitivity analysis to maximize energy allocation within a given group when compared to the nearest one. This method was applied on four frequencies (38, 70, 120 and 200 kHz) data collected in the coastal and oceanic ecosystems of Northeast Brazil; an area characterized by a high biodiversity. By applying the method we discriminated six groups: Fish like, two types of High Resonant at 38 kHz associated with gelatinous, Fluid Like associated with crustacean macrozooplankton, High Resonant at 70 kHz associated with algae, and a group of Unclassified echoes. Results are coherent in terms of distribution pattern of each group. Among other, our results reveal that gelatinous are the dominant group close to oceanic islands where they form a dense layer above the thermocline. These results open new perspectives to improve knowledge on the patterns of distribution and the interaction of a variety of functional groups in different ecosystems.
The acoustic characteristics of bubbly liquids near the individual bubble resonance frequency
Authors: Wilson Preston S. , Roy Ronald
Published: June 2017

In biomedical, naval and oceanographic arenas, the acoustic characteristics of bubbly liquids have simultaneously confounded and been exploited by acoustic tools used in the respective fields. The work of Carstensen and Foldy [J. Acoust. Soc. Am. 19, 481-501 (1947)] served as a cornerstone of the post-World War II understanding of this system, but at high bubble concentrations near the individual bubble resonance frequency (IBRF), the quantitative prediction and measurement of bubbly liquid sound speed and attenuation remains an open topic. In 1989, Commander and Prosperetti [J. Acoust. Soc. Am. 85 732-746 (1989)] advanced the field with a rigorous model valid at the IBRF but it was limited to low void fractions. The data available in 1989 did not corroborate their model at IBRF, but at the time, it was unclear whether this was due to model or experimental deficiencies. This paper reviews an impedance tube measurement [J. Acoust. Soc. Am. 117, 1895-1910 (2005)] that did validate the model for bubble volume fractions up to about 10-4, and also reviews more recent work associated with an industrial underwater noise mitigation system, that validates their model up to void fractions exceeding 10-2, significantly higher than expected.
Quantifying uncertainties in predicting aircraft noise in real-world situations
Authors: Biwalkar Manasi , Sparrow Victor
Published: June 2017

A relatively new project in the ASCENT Center of Excellence at Penn State and Purdue is focused on validating aircraft noise models and quantifying uncertainties of both model prediction and measurement. Multiple data sets are being identified for the validation efforts, and these will be described. This presentation will particularly focus on the BANOERAC and Vancouver Airport Authority data sets. Meteorological influences are very important in assessing the uncertainties on received sound levels from aircraft, so having weather data in conjunction with sound level measurements is essential. An ultimate outcome of the project will be a better understanding of the needs for acoustic and meteorological data to validate modern aircraft noise propagation tools such as the FAA's Aviation Environmental Design Tool (AEDT) and the parabolic equation (PE) algorithm. [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]