bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating sea-water volume attenuation coefficients from mid-frequency, deep-water experiments in the Atlantic and Pacific
Authors: Tippmann Jeffery D. , Sarkar Jit , Verlinden Chris , Hodgkiss William S. , Kuperman William A.
Published: May 2016

A collection of mid-frequency deep-water experiments were performed off the U.S. Pacific coast and in the northeastern Atlantic using a short vertical array cut for 7.5 kHz. Previously presented analysis of a Pacific experiments have shown agreement between experimental estimates of attenuation coefficients to the decades old attenuation models. We present the comparison of experimental attenuation coefficient estimates from additional Pacific and Atlantic data and discuss the methodology for inverting for depth-dependent ocean properties using acoustic amplitude measurements. The data and methodology are also used to explore the feasibility of ocean acoustic attenuation tomography for determining the individual chemical attenuation coefficient terms strictly from in situ measurements.
Optical property changes in ex vivo tissues exposed to high-intensity focused ultrasound
Authors: Raymond Jason L. , Edwards Eleanor , Cleveland Robin O. , Roy Ronald A.
Published: May 2016

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Baseline changes in optical properties have been previously measured as a function of thermal-dose for tissues exposed to a temperature-controlled water bath (doi:10.1088/0031-9155/59/13/3249). In this work, the wavelength-dependent optical scattering and absorption of ex vivo tissues exposed to HIFU were measured using an integrating sphere spectrophotometric technique employed previously. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. We consider the impact of thermal dose, temperature elevation, and heating rate on the formation of HIFU lesions and the resulting changes in tissue optical properties. Recently, reported results (doi:10.1088/0031-9155/59/13/3249) refute the hypothesis that optical property changes in tissue are based solely on accumulated thermal dose—this claim will be explored further through the optical characterization of lesions formed in clinically relevant tissues. Results will show how wavelength-dependent optical property changes in tissues can be used to improve the AO sensing of lesion formation during HIFU therapy as an alternative to thermometry. [Work supported by the ASA F.V. Hunt Fellowship and the University of Oxford.]
A method to suppress harmonics in standing-wave thermoacoustic engines
Authors: Ibrahim A. H. , Emam M. , Fouad A. M. , Abdel-Rahman Ehab
Published: May 2016

Harmonic generation in thermoacoustic engines is regarded as a non-linear loss mechanism that extracts acoustic power from the fundamental wave into harmonics. It is shown that the use of specifically designed insert that limits the gas flow area over a very-limited part of the resonator can suppress this non-linear loss mechanism causing a significant increase in the generated acoustic power in the fundamental mode. In this experimental work, a standing-wave thermoacoustic engine is built and operated without inserts and with inserts of different shapes, porosities, and thicknesses. The self-generated dynamic pressure waves are captured under different operating conditions and then are decomposed into a fundamental component and harmonics. Results for different inserts are presented and discussed. All inserts caused lower harmonic content with respect to the no-insert case but inserts of low gas flow area cause severe flow blockage and thus a severe reduction in the produced acoustic powers. Results analyze the relationships between the generated acoustic power in the fundamental mode and the amplitudes of the dynamic pressures of the fundamental, first harmonic, and second harmonics. The blockage effects caused by the insert are discussed.
Optimizing an underwater transmit array of projectors with large variations
Authors: Noh Eunghwy , Chun Wonjong , Ohm Won-Suk , Seo Youngsoo
Published: May 2016

Uniformity of constituent projector elements is a prerequisite for building a high-performance underwater transmit array. Unless the element-to-element variations in transmitting voltage response (TVR) and directivity fall within specified limits, the resulting acoustic performance of the array will suffer significantly in terms of its sound output and directivity. Here, we consider a case in which projector elements exhibit a large scatter in TVR, say, over 6 dB, and present a design guide to still get the most of the array. The focus of the study is to explore how the relative placement of projector elements affects their mutual interaction and ultimately leads to the overall characteristics of the array. Finite element computations are carried out to derive an optimized design and the design guide. [This work has been supported by the Low Observable Technology Research Center program of Defense Acquisition Program Administration and Agency for Defense Development.]
Nonlinear dynamics helps explain how vowel influences register stability
Authors: Maxfield Lynn M.
Published: May 2016

Highly trained singers know what a registration shift feels like, where in their ranges it is likely to occur, and how to make small adjustments to make it less abrupt. They also know that the location of register changes differs depending on vowel choice and the style in which they are performing. Changing registers while singing can result in a significant timbral shift and, if approached unexpectedly, an abrupt jump in fo. If the source and filter interact in a purely linear fashion, fo should not be influenced by the shape of the vocal tract (vowel). This paper will demonstrate how nonlinear source-filter coupling may explain the strong relationship between vowel and registration. Eight volunteers performed fo glides while altering the dimensions of their vocal tracts, predictably changing the formant frequencies. It was hypothesized that if the source and filter operated as a purely linear system, fo stability should not be perturbed by formant/harmonic crossings in a linear system. Acoustic analysis revealed, however, that 85% of fo instabilities were aligned with a crossing of one of the first four harmonics with the first three formants, indicating that source-filter coupling likely occurred.
Investigating the feasibility of using mobile devices for remote noise monitoring and data acquisition
Authors: Dickerson Mike
Published: May 2016

The feasibility of using the Faber Acoustical SoundMeter Pro app for mobile devices for remote noise monitoring and data acquisition was evaluated and tested. A data file acquisition protocol was created, a remote database storage system was developed, and a reporting system was prepared to test the feasibility. The data and results of this assessment are presented and discussed.
Effect of auditory-motor mapping training and speech repetition training on consonant and vowel accuracy in minimally verbal children with autism spectrum disorder
Authors: Chenausky Karen V. , Norton Andrea , Schlaug Gottfried
Published: May 2016

Various therapies exist for teaching first words to minimally verbal (MV) children with autism spectrum disorder (ASD). Previous outcome measures have focused on number of words imitated or produced spontaneously, or on communication rate. No studies thus far have examined phonetic accuracy in MV ASD as a result of therapy, yet understanding whether therapy improves articulation in MV ASD is important for understanding how speech is affected in ASD and how best to treat these children. In this preliminary study of 30 children with MV ASD, we report on perceptual analysis of their speech after 25 sessions of one of two therapies, employing bisyllabic stimuli with a variety of consonant types. Twenty-three children received Auditory Motor Mapping Training (AMMT), where stimuli are intoned at approximately one syllable per second. Seven children, matched on age and cognition to 7 AMMT participants, received Speech Repetition Training (SRT), where non-intoned stimuli are presented at a normal speech rate. ANOVAs indicated that AMMT resulted in greater gains in consonant production accuracy than SRT. Both therapies produced equally significant improvement in vowel accuracy. Additional, ongoing analyses concern participants’ accuracy for different consonant types, investigating whether accuracy is greater for earlier-appearing than later-appearing consonant types.
Exploring the effects of masker spectro-temporal coherence on the informational masking of speech
Authors: Roberts Brian , Summers Robert J.
Published: May 2016

The effect of an extraneous formant on intelligibility is influenced by the depth of variation in its frequency contour. This study explored whether masker impact also depends on spectro-temporal coherence, using a method ensuring that interference occurs only through informational masking. Three-formant analogs of natural sentences were generated using a monotonous periodic source. Target formants were presented monaurally; the target ear was assigned randomly on each trial. A competitor for F2 (F2C) was presented contralaterally; listeners must reject F2C to optimize recognition. In the reference condition, F2C was created by inverting the F2 frequency contour and using a constant RMS-matched amplitude contour. In the coherent conditions, the F2C frequency contour was preserved but the amplitude contour was divided into abutting 100- or 200-ms segments using a raised-cosine envelope (10-ms rise/fall); these values were informed by typical syllable durations. Segment order was randomized in the incoherent conditions, introducing abrupt discontinuities into the F2C frequency contour. Adding F2C lowered keyword scores, but to the same extent for the reference, coherent, and incoherent conditions. This suggests that the impact on intelligibility depends critically on the overall extent of frequency variation in the interferer, but not on its spectro-temporal coherence. [Work supported by ESRC.]
Subarray compressive beamforming for midfrequency active sonar on a cylindrical array
Authors: Botts Jonathan , Summers Jason E. , Gaumond Charles F.
Published: May 2016

Subarray compressive beamforming is adapted to a cylindrical array for midfrequency active sonar detection of low-Doppler targets in reverberant environments. Low Doppler targets are difficult to detect due to spreading caused by side-lobes and the width of the main lobe. Compressive beamforming and, in particular, subarray compressive beamforming will be shown to drastically mitigate Doppler spreading and interference from static objects. A straightforward application of compressive beamforming to simulated data results in nearly perfect suppression of spread due to sidelobes and good isolation of low Doppler targets from the zero Doppler ridge. Artificially subdividing the array allows for multiple fully resolved sparse estimates of the incident sound field. The set of estimates from the set of subarrays may be combined to form a single sparse estimate, often fully suppressing zero Doppler clutter. Performance of both compressive beamforming and subarray compressive beamforming will be demonstrated using simulated data having realistic Doppler spreading due to multipath and environmental sources of Doppler spreading. Performance will be compared to conventional beamforming methods on the cylindrical array. In addition to practical applications, some theoretical challenges with adaptation to the cylindrical array will be discussed. [Work supported by a NAVSEA Phase I SBIR award.]
Three-dimensional underwater target localization with circular vector sensor array in strong reverberation environment
Authors: Yu Ge , Piao Shengchun
Published: May 2016

As reverberation can be regarded as an output of time-varying stochastic filtering of the emitted signal, it always leads to high false alarm in shallow water. In this case, some methods have been used to suppress reverberation such as empirical mode decomposition filter, match filter, etc. However, a strong correlation between transmitted signal and reverberation restricts the performance of these methods. In this paper,a novel method based on a circular vector sensor array is proposed to detect and locate multiple targets, respectively, in a strong reverberation environment by using the difference of the Doppler shift distribution between reverberation and target echo. First, spherical harmonic decomposition and beamforming are used to process the wideband signal and generate multiple beams which contain spatial information of interested region. Then, fractional Fourier transform is adopted to get Doppler shift distribution and localization information of reverberation and target echo. Multiple targets can be detected and located separately by estimating variance fluctuation associated with the reflections in different beams. Simulation result shows that this method performs efficiently and reliably in server reverberation environment without any prior information.
Circular synthetic aperture sonar images of backscattering enhancements on solid elastic cubes due to Rayleigh waves and other mechanisms
Authors: Bollen Viktor , Plotnick Daniel S. , Marston Philip L.
Published: May 2016

Aspect dependent backscattering enhancement mechanisms aid in detecting and identifying underwater objects. This work examines enhancement mechanisms on a solid metal cube observed in acoustic images, emphasizing Rayleigh type surface waves that undergo retroreflection at the corners of the face of the cube [K. Gipson and P. L. Marston, J. Acoust. Soc. Am. 105, 700–710 (1998)]. Backscattering from a steel cube insonified in water was measured using a circular synthetic aperture sonar system. Image reconstruction was performed using Fourier based algorithms. Rayleigh waves are launched on a face of the cube when the local incident angle is equal to the Rayleigh coupling angle. The presence of four right-angle retroreflectors on each face means that multiple reverberations of this wave are observed. In reconstructed images of the cube, the Rayleigh wave mechanism is responsible for some of the brightest features. If the relative orientation of the circular aperture and the cube is such that specular glints are suppressed, edge and corner diffraction features are clearly observed. This relative orientation may be deduced from the reconstructed image. Discussions of both the spectral response and temporal response of the cube as a function of viewing angle will also be included. [Work supported by ONR.]
A comparison of the predictions of two competing sediment acoustic models for the scattering from inclusions in a sandy sediment
Authors: Bonomo Anthony L. , Isakson Marcia
Published: May 2016

Currently, there are several competing models that have been used to describe the acoustic properties of sandy sediments. These models include those that assume the sediment to behave as an acoustic fluid, a viscoelastic solid, and as a porous medium following Biot theory. Perhaps the two most sophisticated acoustic models that have been applied to sand are the Viscous Grain Shearing (VGS) model of Buckingham and the Extended Biot (EB) model of Chotiros. While both of these models have been used to fit measured sound speed dispersion and attenuation data, the reflection and scattering predictions made using these models differ. In this work, the finite element method is used to compare the scattered pressure predictions of these two models for the case of a sand half-space with a single inclusion. The geometry is assumed axisymmetric, and the inclusions are allowed to be either a fluid or an elastic solid. [Work supported by ONR, Ocean Acoustics.]
Statistics of near surface underwater scattered sound including wave induced Doppler
Authors: Walstead Sean
Published: May 2016

The interaction of underwater sound with the ocean surface is explored. Analytic expressions for the Doppler shift and Doppler spread of surface reflected signals are developed. Statistical models for surface scattered intensity, arrival time, and Doppler fluctuations are developed in relation to wave shape, transducer position, and transmission frequency. Measurements from two experiments are considered. Data collected from AUTEC explore surface scattering effects in the frequency regime of 8 kHz–10 kHz, while data collected in a variable speed wind wave channel at Scripps Institution of Oceanography explore scattering statistics in the 200 kHz–400 kHz (VHF) frequency regime. Physics based analytic expressions for the equations of motion of specular reflection points (SRPs) along a time-evolving wave surface are derived. The time-varying Doppler shift of VHF underwater acoustic signals is attributed to SRP motion associated with surface wave propagation. Model predicted values are compared to experimental measurements and differences between the two tested frequency regimes are highlighted. This work has direct application to the improved performance of phase coherent underwater acoustic communications systems and the remote sensing of gravity-capillary waves.
Utilizing the sound of predators to cast out wild animals
Authors: Kim Myungsook , Ahn Ik-Soo , Bae Myung-Jin
Published: May 2016

Recently, there have been many reports of damages caused by animals such as wild pigs and wild dogs in the rural farms of Korea. Damages were extensively widespread from agricultural crop and produce to domestic animals. To efficiently cast out wild animals, the recorded sound of predators such as lions and tigers was used. The speakers were installed around the farms and broadcasted the sound of predators every 3 h. Although the damages were a little bit reduced after broadcasting, it did not complete its purpose and still some damages were reported. We analyzed the recording quality of the sound and found out some deficiencies in it, the lack of low frequency sound below 100 Hz in particular. In order to improve its sound quality, we installed the speakers inside of water pipes with 1 m in diameter. As a result, we earned 90% in the index of similarity between the original crying sound and the broadcasted crying sound of predators in its sound spectra. Since the improved sound recording was broadcasted for 1 min every 3 h in the farms, the damages have not been reported.
Comparison of pressure-based intensity measurements for different probe designs and estimation methods
Authors: Rose Michael T. , Torrie Darren K. , Rasband Reese D. , Gee Kent L. , Sommerfeldt Scott D.
Published: May 2016

Acoustic intensity measurements have traditionally used cross spectral methods with multimicrophone probes to estimate the required pressure and particle velocity. The phase and gradient estimator (PAGE) method increases probe bandwidth without modifying microphone spacing as compared to the traditional cross spectral method [D. C. Thomas et al., J. Acoust. Soc. Am. 137, 3366–3376 (2015)]. In this study, high-frequency probe bandwidth obtained using both the PAGE method and the traditional method is compared across three different multimicrophone probe designs: a three-axis, six-microphone probe with variable solid spacer, a three-axis, four-microphone spherical probe, and a two-axis, four-microphone probe developed in-house for rocket measurements. Broadband, anechoic loudspeaker measurements are used to examine the performance of each probe and estimation method. These include a single 7.6 cm diameter, enclosed loudspeaker driver, and two drivers of equal strength but opposite phase. Intensity measurements in a grid of 41 × 41 points inside a one square meter area are presented. Probe design robustness is determined by considering bias errors in calculation methods and probe scattering. [Work supported by NSF.]
Pitch control in professional and amateur singers
Authors: Bottalico Pasquale , Graetzer Simone , Hunter Eric J.
Published: May 2016

One aspect of major relevance to singing is the control of fundamental frequency. Ten amateur and ten professional singers sang two-octave arpeggi with three different levels of external auditory feedback, two tempi and two articulations (legato or staccato). The effects on pitch inaccuracy (defined as the distance in cents between the reference note and the sung note) of the following conditions were evaluated: (1) level of external feedback, (2) tempo (slow or fast), (3) articulation (legato or staccato), (4) tessitura (low, medium, or high), and (5) semi-phrase direction (ascending or descending). It was observed that inaccuracy was greatest in the descending semi-phrase arpeggi produced at a fast tempo and with a staccato articulation, especially for non-professional singers. The magnitude of inaccuracy was also relatively large in the high tessitura relative to the low and medium tessitura for such singers. Counter to predictions, when external auditory feedback was strongly attenuated or canceled by the hearing protectors, non-professional singers showed greater pitch accuracy than in the other external feedback conditions, which indicates the importance of internal auditory feedback in pitch control. With an increase in training, the singer's pitch inaccuracy decreases.
How singing experience affects the “brightness” of humming?
Authors: Yang Ae Na , Takabayashi Marina , Itagaki Sachi , Kikuchi Hayato , Kobayasi Kota
Published: May 2016

During singing practice, people are often told to sing in bright voice to improve singing performance. The purpose of this study is to determine how singing practice affects the acoustical characteristics and expressiveness of “brightness.” In this study, eight singers (having experience in chorus for 0 to 13 years) sang three types of humming with G4 (392 Hz). Singers were told to sing either “bright,” “dark,” or “normal” humming. Subjects (n = 16) listened to different types of humming in pairs, and judged which was brighter. The results showed that the subjects perceived “bright” humming as bright. As singers practiced longer, their “brightness” was more expressive. Acoustical analysis revealed that fundamental frequencies of “bright” humming were higher than dark humming by 3 Hz, and that bright humming had higher amplitude in spectrum from 4900 to 6400 Hz by 4.5 to 6.5 dB. In the following experiment, subjects listened to and judged the brightness of humming, whose amplitude in the range was systematically amplified. As a result, the more amplified the humming had in the range, the more likely subjects evaluated it as bright. Our results suggest that singers can obtain the ability to express “brightness” by producing these acoustical characteristics through practicing singing.
On-chip generation of acoustical vortices with swirling surface acoustic waves for single particle manipulation and vorticity control
Authors: Riaud Antoine , Baudoin Michael , Thomas Jean-Louis , Bou Matar Olivier
Published: May 2016

Surface acoustic waves (SAWs) are versatile tools for the manipulation of fluids at small scales. These waves can be used to displace, divide, merge, and atomize sessile droplets, but also actuate fluids embedded in microchannels. In this presentation, we will show that IDTs array and inverse filter technique enable on-chip synthesis of a new type of SAWs, called swirling SAWs, which degenerate into bulk acoustical vortices when transmitted to a liquid. These acoustical vortices can be tailored to create a 3D particle trap and thus selective single particle acoustical tweezers, with digital control of the trap position. They can also induce controlled vortical flows, whose topology essentially relies on the topology of the underlying acoustical vortex.
Sound characteristic analysis of sound-pipe-breakwater on the east-coast in Gangneung South Korea
Authors: Park Hyungwoo , Lee Won-Hee , Kim Myung-Sook
Published: May 2016

There is mysterious sounds which can hear after 2010 the new breakwater construction, in a small port city “Yung-Jin” of Gangneung East Sea of Korea. In particular, the mysterious sounds are spread loud honk, when north-east wind are blown in fall and winter of the seasons. People, who have heard the sound that is regarded as a sinister sound, called that like “Kelpie sound,” “Sea whistle,” and “Pipe sound.” This is an ordinary concrete breakwater structure, which has prevented the waves by rocks and tetrapods. The waves are usually considered wind-driven waves. The wind and waves were blocked in rocks and tetrapods. In this time, the wind causes a vortex by the tetrapods. The waterway of the inner harbor and the ocean filter a particular sound out. We can hear and analyze the Mysterious Sound of sound-pipe-breakwater, although the design of the breakwater is not to produce sound. In this study, we investigate and analyze the truth of the strange noises of breakwaters.
Processing of defective ring data by “super-interpolators”
Authors: Martinez Rudolph
Published: May 2016

We develop an analytical-numerical scheme to make up for full or partial sensor failures in a ring array. The technique’s goal is to restore missing information to a recorded signal in the form of a Hermitian covariance matrix for an arbitrary dependent variable. Our analysis breaks the problem down into two: first, by considering the special case of an imperfect array in which the positions and degrees of failure of the flawed sensors are known, and, second, by generalizing that approach to one in which neither piece of information is presumed nor in fact is the knowledge of how many sensors are affected required. An important application of the first part is the retrieval of the perfect signal at equispaced points that have been left un-instrumented for reasons of economy or lack of physical access (a missing sensor becomes equivalent to one with a known null gain). The problem’s more general second part has led to a fundamental relationship for a periodic array’s total number of sensors, the bandwidth of the ideal signal being restored, and the rank of an integral equation developed from one of Fourier series’ dual statements of orthogonality. We call the products of our two-tier technique “super-interpolators” even though neither engages in that activity mathematically.
The role of rhythm perception in recognition and learning of disordered speech
Authors: Borrie Stephanie A. , Lansford Kaitlin L.
Published: May 2016

The musical advantage describes the idea that musicians, relative to non-musicians, are more successful at deciphering speech in challenging listening conditions. One assumption is that fine-tuned rhythm perception skills in the musical domain translate to fine-tuned processing of rhythm cues in the speech domain. But what happens when the rhythm cues afforded by the speech signal are, themselves, disordered? This study investigated whether the ability to perceive musical rhythms provides a perceptual advantage for recognition (initial intelligibility) and learning (intelligibility improvement) of dysarthric speech—a neurologically degraded acoustic signal characterized by rhythm abnormalities. Fifty young, normal hearing adults participated in two key tests including a rhythm perception test and a perception and learning test with standard pretest, training, and post-test phases. Initial intelligibility scores for each participant reflected words correct on the pretest, and intelligibility improvement scores reflected post-test words correct minus pretest words correct. The results revealed that rhythm perception scores predicted intelligibility improvement scores but not initial intelligibility scores. Findings are discussed in relation to theoretical models regarding the link between music and speech processing, and offer direction for new models that consider the perceptual consequence of rhythm abnormalities in disordered speech.
Simultaneous tracking and counting of targets in a sensor network
Authors: Chattopadhyay Pritthi , Ray Asok , Damarla Thyagaraju
Published: May 2016

Unattended ground sensors (UGS) are widely used to monitor human activities, such as pedestrian motion and detection of intruders in a secure region. This paper presents an algorithm for counting and tracking humans moving through a UGS network. Each node of this sensor network is equipped with a geophone (i.e., seismic sensor) and a microphone (i.e., acoustic sensor). The proposed method analyzes the relational dependence among the responses of sensors at various nodes as the targets walk through the network. The energy distribution across the network for different number of targets walking at different distances from the nodes has been analyzed to predict the number and location of targets in the sensor network field. The proposed concept has the advantages of having fast execution time and low memory requirements and is potentially well-suited for real-time implementation on in-situ computational platforms. Keywords—Personnel detection, seismic sensing, acoustic sensing, sensor-network-based fusion.
From macroscopic to microscopic glimpse-based models of intelligibility prediction
Authors: Cooke Martin , Tang Yan , Toth Mate A.
Published: May 2016

Miller and Licklider's explorations of the intelligibility of temporally interrupted speech, and later studies extending their findings to the spectro-temporal plane, have shown how the twin factors of sparseness and redundancy confer a high degree of robustness on speech in noise. The current contribution addresses two questions. First, to what extent can quantitative estimates of supra-threshold unmasked speech account for average (macroscopic) intelligiblity across a range of speech styles and masking conditions? We examine how well glimpse-based objective intelligibility metrics predict listeners' speech recognition scores for natural and synthetic speech in the presence of stationary and fluctuating maskers, and demonstrate reduced correlations for competing sources with an informational masking component. The second question concerns which additional components, beyond speech glimpses, are required to make (microscopic) predictions of actual listener confusions at the level of individual noisy speech tokens. Using corpora of speech-in-noise misperceptions, we show that in many cases the source of listener confusions is the misallocation of information from the masker, suggesting that estimates of supra-threshold unmasked speech alone are insufficient to explain speech intelligibility in noise.
Target localization in a reverberant shallow ocean waveguide with environmental uncertainty using a nonlinear frequency-difference signal processing technique
Authors: Worthmann Brian M. , Dowling David R.
Published: May 2016

Model-based signal processing for active sonar localization is typically infeasible due to insufficient knowledge of the acoustic environment. Additionally, in a shallow ocean environment, surface or bottom roughness create diffuse reverberation that can often obscure a desired target echo. Recently, a nonlinear signal processing technique was developed for passive acoustic source localization (Worthmann, et al., 2015) that is applicable to high frequency sources in uncertain shallow ocean environments. This technique exploits a nonlinear field product (the autoproduct) and uses in-band hydrophone array measurements to determine field information in a lower, out-of-band, frequency regime where environmental uncertainties are less detrimental. When extended to monostatic active sonar with a vertical array, this technique allows a model-based signal processing algorithm to combat the detrimental effects of reverberation. The nonlinear signal processing algorithm is presented, along with simulations in a 5-km range, 200-m deep ideal waveguide with environmental uncertainties and significant reverberation at frequencies between 2- and 5-kHz. Successful detection and localization of a mid-water-column target is found to be possible at simulated signal-to-reverberation levels as low as −5 dB. Comparisons to existing signal processing detection and localization algorithms are provided. [Sponsored by the Office of Naval Research and the National Science Foundation.]
Physical modeling sound synthesis using embedded computers: More masses for the masses
Authors: Berdahl Edgar , Blessing Matthew
Published: May 2016

Physical modeling for sound synthesis is a technique in which musical acoustic equations are simulated by computer to synthesize sound. In prior decades, either offline simulation or powerful desktop or laptop computers were required in order to synthesize high-quality sound. However, increasingly small and relatively low power embedded computers are presently becoming available that can natively perform real-time simulations using floating-point computations. For example, the Raspberry Pi 2 is an embedded computer, which incorporates a quad-core 1GHz embedded microprocessor, and currently costs only US$35. This implies that physical modeling sound synthesis may become accessible to a wide range of people for many diverse applications. Furthermore, larger and larger numbers of virtual masses will be computable in real time. A poster with embedded Raspberry Pi 2 and amplified speaker is presented that uses Synth-A-Modeler to simulate a wide variety of physical models in real time.
Active control of noise radiated from an x-ray tube
Authors: Cao Yin , Succo Kelli , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: May 2016

The application of implementing an active noise control system to globally attenuate noise radiated from a medical x-ray tube has been investigated. The noise radiated from the x-ray tube is characterized by the presence of numerous tonal peaks distributed over a broad frequency bandwidth. Furthermore, there is sufficient variability in the radiated field that coherence in the acoustic field was also found to be a challenge. It was determined that a properly placed structural sensor could be used as a reference signal to achieve good coherence between the reference signal and error microphone. In order to achieve global control, speakers were placed in close proximity to areas that had been identified as source regions through the use of SLDV and acoustic intensity measurements. The frequency band below 1500 Hz was targeted, and it was found that effective attenuation could be achieved at over ten of the most prominent frequencies, resulting in attenuations in that bandwidth on the order of 7 dB. Some of the challenges encountered and results obtained will be discussed and presented.
Derivative skewness values of shock-containing noise waveforms
Authors: Reichman Brent O. , Gee Kent , James Michael , Salton Alexandria , Neilsen Tracianne B.
Published: May 2016

Acoustic shocks present in military aircraft noise are often referred to as crackle, a component of jet noise that can significantly alter perception and annoyance. Quantifying the shock content within a waveform is important for gauging possible effects that these shocks may have. In the past, the derivative skewness has been used to quantify the steepening of waveforms throughout propagation, representing average behavior throughout the waveform. Though past use has been mostly qualitative, recent work has given physical meaning to derivative skewness values of sinusoids and provided recommendations on sampling rate and thresholds that can indicate significant shocks within the waveform. Using these recommendations, the derivative skewness of high-performance military aircraft noise is estimated for various locations and engine conditions. Derivative skewness values are compared with shock counting schemes based on various criteria. The comparisons show a strong relationship between high derivative skewness values and the strength and number of shocks within a waveform.
Modeling of the pressure distribution, acoustic streaming, and formation of bubble structures in an ultrasonic horn reactor
Authors: Gadi Man Yezaz A. , Trujillo Francisco J.
Published: May 2016

A framework is developed to simulate the acoustic streaming and the formation of conical bubble structures (CBS) in ultrasonic horn reactors. In these reactors, acoustic pressure waves propagate from the vibrating solid horn to the liquid. On its movements away from the horn, sound is attenuated producing acoustic streaming, which is exacerbated by the presence of inertial acoustic bubbles that diminish the pressure amplitude many fold very near to the acoustic source. This is a complex Multiphysics phenomena occurring at different time and length scales. Inertial bubbles, which have sizes of the order of few micrometers, oscillate, grow, and collapse as function of time within the period of the acoustic wave while acoustic streaming is a time independent hydrodynamic movement of the liquid occurring through the totality of the reactor. The four main phenomena, solid vibration, acoustic pressure, streaming and bubble generation and distribution, are simulated in COMSOL Multiphysics in a stepwise fashion. The first two phenomena are coupled and solved in frequency domain, and the resultant acoustic pressure forces are applied to solve turbulent streaming and a transport equation in time-independent mode. Steps are repeated sequentially until a good agreement is found with experimental CBS, power, and streaming.
Ultrasound directed self-assembly of user-specified patterns of nanoparticles dispersed in a fluid medium
Authors: Greenhall John , Guevara Vasquez Fernando , Raeymaekers Bart
Published: May 2016

We employ an ultrasound wave field generated by one or more ultrasound transducers to organize large quantities of nanoparticles dispersed in a fluid medium into two-dimensional user-specified patterns. To accomplish this, we theoretically derive a direct method of calculating the ultrasound transducer parameters required to assemble a user-specified pattern of nanoparticles. The computation relates the ultrasound wave field and the force acting on the nanoparticles to the ultrasound transducer parameters by solving a constrained optimization problem. We experimentally demonstrate this method for carbon nanoparticles in a water reservoir and observe good agreement between experiment and theory. This method works for any simply-closed fluid reservoir geometry and any arrangement of ultrasound transducers, and it enables using ultrasound directed self-assembly as a scalable fabrication technique that may enable a myriad of engineering applications, including fabricating engineered materials with patterns of nanoscale inclusions.
Real-time polymerization monitoring of a thermosetting resin around its glassy transition temperature
Authors: Ghodhbani Nacef , Marechal Pierre , Duflo Hugues
Published: May 2016

Real-time ultrasonic monitoring is investigated to quantify changes in physical and mechanical properties during the manufacture of composite structures. In this context, an experimental transmission was developed with the aim to characterize a high temperature polymerization reaction and post-curing properties using an ultrasonic method. First, the monitoring of ultrasonic parameters of a thermosetting resin is carried out in an isothermal polymerization process at 160°C. During this curing, the resin is changing from its initial viscous liquid state to its final viscous solid state. Between those states, a glassy transition stage is observed, during which the physical properties are strongly changing, i.e., an increase of the ultrasonic velocity up to its steady value and a transient increase of the ultrasonic attenuation. Second, the ultrasonic inspection of the thermosetting resin is performed during a heating and cooling process to study the temperature sensitivity after curing. This type of characterization lead to identify the ultrasonic properties dependence before, during, and after the glassy transition temperature Tg. This study is composed of two complementary parts: the first is useful for the curing optimization, while the second one is fruitful for the post-processing characterization in a temperature range including the glassy transition temperature.
Photoacoustic spectroscopy with SF6, an optically thick greenhouse gas
Authors: Park Han Jung , Murphy Wittmann S.
Published: May 2016

Photoacoustic spectroscopy was used to test the photoacoustic properties of sulfur hexafluoride, an optically thick and a potent greenhouse gas. Detection of trace amounts of the gas was also implemented. The conditions in which the gas was tested, gas cell length, temperature, concentration, and power of the laser, were varied to determine their effect on the photoacoustic signal, and the ideal conditions to detect trace gas amounts. A detection limit of 2.86 ppb was determined for SF6.
Effect of visual and vestibular information on auditory space perception
Authors: Sakamoto Shuichi , Hanakago Keishi , Cui Zhenglie , Teramoto Wataru , Suzuki Yôiti , Gyoba Jiro
Published: May 2016

We investigated how auditory space would be represented during linear self-motion and visually-induced self-motion (vection) (Teramoto et al., 2012, 2014). The previous studies indicated that the subjective coronal plane (SCP) was displaced during forward self-motion, while during backward motion in the case of vection. The present study investigated how auditory space perception would be altered when both visual and vestibular information were presented. A random-dot pattern simulating linear self-motion was used. At the beginning of the trial, the random-dot pattern started to move at a velocity of ±0.1 m/s. When an observer perceived vection, the velocity was changed at an acceleration of ±0.2, 0, and 0.4 m/s2. At the same time, the observer was moved forward at an acceleration of 0.2 m/s2 by using a linear-motor-driven chair. A short noise-burst was presented from a loudspeaker when the observer moved 2 m. The observers indicated the direction in which the sound was perceived relative to their coronal plane. The results showed that the direction of the SCP shift was different only when the acceleration of both visual and vestibular information was identical. These results suggest that auditory space distortion effect occurs closely related to the integration of vestibular and visual information.
Temporal integration of dynamic binaural events
Authors: Stecker G. Christopher , Stecker Julie M. , Diedesch Anna C. , Higgins Nathan C. , Da Costa Sandra
Published: May 2016

Events occurring in different sensory dimensions (e.g., modalities) and within an interstimulus interval (ISI) of few hundred milliseconds typically appear simultaneous. The temporal “window” of sensory integration can be estimated by increasing the ISI until events appear discrete. Here, we adapt the simultaneity-judgment paradigm to investigate the integration of binaural events within and across dimensions of interaural time and level difference (ITD and ILD). Noise bands (353.5–707 Hz) of 2s duration were presented over headphones to normal-hearing listeners. Each stimulus contained two 10-ms binaural-change events, during which the ITD or ILD changed by 500 µs or 6 dB. Events could occur in the same or different cue dimensions (ITD or ILD), but always agreed in direction (leftward or rightward). ISI varied over the range ±600 ms. Listeners indicated the number and direction of each perceived shift in the lateral image, e.g., one (left-to-right) at short ISI, or two (left-to-center, center-to-right) at long ISI. The threshold for reporting two events was shortest for pairs of ITD events, suggesting greater temporal fidelity for ITD change than for ILD change. Thresholds did not differ between ILD and cross-cue event pairs, suggesting no additional cost of cross-cue integration. [Work supported by NIH R01-DC011548.]
Sensitivity to binaural cues beyond threshold as revealed by eye movements
Authors: Winn Matthew , Kan Alan
Published: May 2016

Binaural cues are paramount for sound localization along the azimuth. Studies on the perception of the critical binaural cues, interaural time and level differences (ITDs and ILDs, respectively), typically measure sensitivity at threshold using N-interval, forced choice paradigms. This approach gives little or no information regarding perceptual abilities beyond threshold. In this study, an anticipatory eye movement (AEM) paradigm (cf. McMurray, 2004) was used as a novel measure to study binaural cue sensitivity throughout a wide perceptual range. This paradigm is sensitive to gradient (rather than all-or-none) perception of auditory cues. Adults with normal hearing visually tracked the location of a ball that becomes hidden on a computer screen, and anticipated its motion and reappearance via eye movements guided by binaural cues. The auditory stimuli were 4.8-s 1/3-octave narrowband noises centered at different frequencies, and contained an ILD or ITD change, indicating the impending motion of the ball. Greater cue levels elicited systematically quicker and more accurate saccades. ILD-driven AEMs were elicited for all noise center frequencies, with greater sensitivity for higher frequency noises, consistent with ecological significance. Eye movements in this study suggest variation in binaural cue perception beyond threshold that is gradient in terms of latency and accuracy.
The role of early and late reflections on spatial release from masking
Authors: Srinivasan Nirmal Kumar , Stansell Meghan M. , Ellinger Rachel E. , Jakien Kasey M. , Kampel Sean D. , Gallun Frederick J.
Published: May 2016

It is well documented that older listeners have more difficulty understanding speech in complex listening environments than do younger listeners. Early reflections (occurring <50 ms following the direct sound) have been linked to improved speech intelligibility (Lochner and Burger, 1964), while later-arriving reverberant sound has been shown to limit speech understanding (Knudsen, 1929). However, we do not know how spatial release from masking (SRM) is affected by early and late reflections or how age and hearing loss interacts with the relative influences of each. SRM in two simulated reverberant environments was measured for listeners varying in age and hearing thresholds under three different signal processing conditions: (1) early reflections alone, (2) late reflections alone, and (3) all reflections. Results indicated that though all listeners performed better when only early reflections were present, the older hearing-impaired listeners benefited the most from the absence of late reflections. Effects of age and hearing loss on performance and SRM under these three different signal processing conditions will be discussed. [Work supported by NIH R01 DC011828.]
On the possible origin of voiceless implosives: Hints from Ese’eja (Takanan)
Authors: Demolin Ddiier , Wuillermet Marine
Published: May 2016

Voiceless implosives are reported in a few languages of Africa, Mesoamerica, and Amazonia. Ese’eja (Takanan) has bilabial [ɓ̥] and [ɗ̥] alveolar voiceless implosives in its phonemic inventory (Vuillermet 2006). These sounds are realized with a complete closure of the vocal folds, a lowering of the larynx during the glottal closure associated with a lowering of the pressure (Po) inside the vocal tract behind the labial or alveolar closures. This is followed by a rapid larynx rising. The acoustic characteristics are: a period of silence and a short prevoicing preceding a strong final burst. There are two possibilities to explain the origin of voiceless implosives in Ese’eja. The first is that they are the consequence of the devoicing of a voiced implosive. The second is that they are due to the combination of a glottal closure and a voiced stop. The lowering of the glottis and Po is anticipating the articulation of a following low or back vowel during the glottal closure. Voiceless implosives have been described as preglottalized stops in other languages. (Dimmendaal 1986) emphasizes that in Lendu there is a possible auditory confusion between voiceless implosives and preglottalized stops. Aerodynamic and acoustic measurements confirm this hypothesis for Ese’eja.