bluuebunny/crossref_metadata_2025 huggingface dataset:
Pause length and speech rate as durational cues for prosody markers
Authors: Choi Jeung-Yoon
Published: October 2013

Two durational cues for prosody are examined for utterances in the Radio Speech Corpus. The acoustic cues are length of pause and speech rate associated with each syllabic segment. Pauses are defined as intervals where probability of voicing and energy (rms) fall below respective thresholds. Speech rate is defined as the reciprocal of the duration of the syllabic segment, without normalization with respect to speaker or segment identity. Each syllabic segment was assigned prosodic markers that are a combination of degree of accent and boundary, i.e., {unaccented, accented} × {nonboundary, intermediate boundary, intonational boundary}. Distributions of pause length and speech rate for each type of prosodic marker show that in general, mean pause length increases and speech rate decreases as the strength of the boundary increases from nonboundary to intonational boundary. Accented syllabic segments at intermediate or intonational boundaries showed longer associated pause length and slower speech rate than unaccented segments. Also, for different types of intonational boundary tones, mean pause length decreases in the order of: L-L%, H-H%, H-L%, L-H%. Preliminary classification results using the two durational cues show detection rates for intonational boundaries around 75%, with insertion rates around 25%.
Pure-tone audiograms and hearing loss in the white whale (Delphinapterus leucas)
Authors: Finneran James J. , Carder Donald A. , Dear Randall , Belting Traci , Ridgway Sam H.
Published: October 2013

A behavioral response paradigm was used to measure pure-tone audiograms for two white whales (Delphinapterus leucas). Tests were conducted over a 20 month period at the Point Defiance Zoo and Aquarium, in Tacoma, Washington. Subjects consisted of two males, aged 8–10 and 9–11 during the course of the study. Subjects were born in an oceanarium and had been housed together for all of their lives. Hearing thresholds were measured using a modified up/down staircase procedure and acoustic response paradigm where subjects were trained to whistle in response to hearing test tones and to remain quiet otherwise. Test frequencies ranged from approximately 2 to 130 kHz. Best sensitivities ranged from 40 to 50 dB re: 1 Pa. Both subjects had traditional U-shaped mammalian audiograms; however, one subject exhibited significant high-frequency hearing loss, above approximately 37 kHz. The experimental setup and procedure will be presented and the measured hearing thresholds compared to those previously measured in white whales. The potential role of ototoxic antibiotics in the observed hearing loss will be discussed. [Work supported by ONR Marine Mammal S&T Program and the U.S. Navy CNO(N45).]
Modal analysis of violin bodies viewed as three-dimensional structures
Authors: Rossing Thomas D. , Molin Nils-Erik , Runnemalm Anna
Published: October 2013

Modal analyses of violins show several strong modes in the low frequency range. Holographic interferograms suggest that four strong modes can be interpreted as doublets having two and three nodal planes that intersect a cylinder with a roughly elliptical cross section at the bridge [A. Runnemalm, N.-E. Molin, and E. Jansson, J. Acoust. Soc. Am. 107, 3452–3459 (2000); M. Roberts and T. D. Rossing, Catgut Acoust. Soc. J. 3, 9–15 (1998)]. This is especially clear when the instrument is viewed simultaneously from three sides using mirrors, and the holographic system is made sensitive to in-plane motion as well. These doublets are not unlike those observed in cylindrical vibrators such as bells, and they remind us that a violin is a 3-dimensional object.
Using the ideal function concept for machine noise control
Authors: Landsberger Brian
Published: October 2013

An engineered system reaches its ideal function when all its input energy is transformed efficiently into creating the output energy. This leaves less energy available for creating unwanted noise and vibration. A large hydraulic pump evaluation is used to demonstrate the relation between energy efficiency and unwanted noise. Measurements were taken while conducting speed sweeps at various load conditions. Sound in the hemisphere surrounding the pump, acceleration at various locations on and around the pump, and shaft rotation instantaneous phase measurements were used to determine the magnitude, character, and source of the sound. A particularly loud noise level associated with a certain operating region was determined to result from driven vibration of the pump case. The disturbance appeared to originate from pulsations in the pump flow and pressure. This operating region also had a several percent drop in pump efficiency. In this example, more efficient energy transformation would have the dual benefit of higher efficiency and lower noise.
Sound propagation in an urban environment. I: Preliminary analysis of measurements
Authors: Albert Donald G. , Liu Lanbo
Published: October 2013

Experimental measurements were conducted in a full-scale artificial village to determine the effect of buildings on sound propagation outdoors. The village consisted of 15 concrete block buildings arranged in a 150×150 m area. Explosive charges were detonated to produce acoustic pulses that were digitally recorded by sensors scattered throughout the village. The measurements confirm that diffraction acts as a low pass filter on acoustic waveforms, greatly reducing the peak pressure received by a sensor in the shadow zone. The measured data present clear examples of the effect of reflections on propagation down a street canyon and diffraction around building corners. Complex signatures formed by multiple reflections and diffractions were recorded in situations where the acoustic waves passed multiple buildings in propagating from the source to the receiver. [Work funded by the U.S. Army.]
Application of multisource discrimination to the HELS method
Authors: Rayess Nassif , Moondra Manmohan , Wu Sean
Published: October 2013

In most engineering applications, the acoustic fields are usually generated by multiple incoherent sources. When such acoustic fields are sampled and taken as input data to the Helmholtz equation least-squares (HELS) formulations directly, the reconstruction might not be accurate. Hence there is a need to discriminate the contributions from individual sources and separate the composite sound field into a set of spatially coherent subfields that are also mutually incoherent. In this paper, we apply the principal component decomposition technique to the HELS method to reconstruct acoustic radiation from multiple incoherent sources in a free field. The key ingredients of this technique include a diagonalization by singular value decomposition (SVD) of the cross-spectral matrices generated by a number of reference microphones. Each diagonal term corresponds to a subfield that results from a so-called virtual sound source. Even though such virtual sources are not always representative of the actual sources, they are nonetheless incoherent and thus can be used as input to HELS. Experimental validations of this technique on reconstructing acoustic pressure and time-averaged normal acoustic intensity on the surfaces of multiple incoherent sources are presented. [Work supported by NSF.]
Distributional and statistical bases of allophonic groupings
Authors: Morgan James L. , White Katherine S. , Kirk Cecilia , Peperkamp Sharon , Dupoux Emmanuel
Published: October 2013

Segments of a given language do not all have equal status: some are phonetic variants of others. These variants occur only in certain contexts. In addition to occurring in more restricted contexts, however, variant allophones typically occur with lesser frequency. Which (if either) of these asymmetries is important for infants learning of allophonic groupings? Infants were exposed to artificial languages with allophones. Either stops or fricatives were intervocalicly voiced; these voiced segments did not otherwise occur. Infants were then tested on preference for passages like ‘‘rot pazo na bazo rot pazo na bazo’’ or ‘‘na zine rot sine na zine rot sine...’’ All items were grammatical for both groups. For the stop allophone group, /pazo/ and /bazo/ should be one word, whereas /zine/ and /sine/ should be two words; vice versa for the fricative allophone group. In previous work using a similar technique, infants listened longer to passages containing what was perceived as two variants. Across a series of experiments, the number and frequency of contexts in which allophonic variants occurred were manipulated. Cross-experiment analyses reveal the relative contributions of distributional and statistical asymmetries. We interpret and discuss our findings in light of current statistical learning approaches to language acquisition.
Phonotactic probability and neighborhood density effects in the perception and production of speech in adults
Authors: Vitevitch Michael S. , Armbruster Jonna , Fitzer Julia
Published: October 2013

Phonotactic probability refers to the frequency with which phonological segments and sequences of segments occur in a language. Neighborhood density refers to the number of words that sound similar to a given word. Awareness to phonotactic probability and neighborhood density occurs early in life and seems to influence lexical development. Recent research in our lab suggests that these two variables also influence the on-line processing of spoken words in adults. In the case of spoken word recognition, when sub-lexical representations dominate processing, high probability stimuli are responded to more quickly than low probability stimuli. However, when lexical representations dominate processing, stimuli with sparse neighborhoods are responded to more quickly than stimuli with dense neighborhoods. Similarly, in speech production, pictures of high probability words are named more quickly than pictures of low probability words. However, in contrast to speech perception, pictures of words with dense neighborhoods are produced more quickly than pictures of words with sparse neighborhoods, suggesting that statistical regularities in the language may be used differently depending on the demands imposed by a given process or task.
The effects of distributional information on the formation of nonspeech sound categories by infants
Authors: Hay Jessica F.
Published: October 2013

In order to learn native sound categories, infants may be attending to the distributional information available in their native language environment. The present study examined eight-month-old infants ability to form categories with small amounts of exposure to distributional information. Infants were exposed to a bimodal distribution of nonspeech sounds (narrow-band noise bursts that vary in center frequency). Their ability to discriminate within (same mode) and between category (different mode) differences was then assessed through a habituation-dishabituation procedure. Data were interpreted in terms of dishabituation to change stimuli. The change stimuli were equal in physical step size and either came from within the same mode of the bimodal distribution or from the other mode. The findings may have implications regarding auditory category formation in general and could lend support to the hypothesis that infants use distributional information available in their ambient language environment to learn their native speech categories. [Work supported by NIDCD.]
Field measurements of attenuation and permeability of shallow water sediments
Authors: Yamamoto Tokuo , Sakakibara Junichi
Published: October 2013

The velocity and attenuation of sands and clays in shallow oceans were measured by cross-hole tomography experiments using the pseudo-random binary sequence (PRBS) as source signals with the PRBS frequency of 1 and 3 kHz. Using measured velocity images, 2D velocity and density fluctuation spectra were calculated. The acoustic attenuation due to scattering by velocity and density fluctuations in the sediment volume was calculated using the measured velocity and density fluctuation spectra. The attenuation due to scattering occupies 30 to 98% of the total attenuation measured during the field experiments. The intrinsic attenuations of sands and clays were 0.3 to 1.5 dB/m/kHz and 0.01 to 0.02 dB/m/kHz, respectively. The permeability of the sands and the clays inverted by the Biot theory is 2.0 to 14.0 darcy and 0.1 to 120 md, respectively. The acoustically inverted permeability values agreed very well with the direct measurements of permeability of the sediments. The experimental results indicate that the acoustic attenuation measured in the fields is mainly due to volume scattering and that the intrinsic attenuation is due to the Biot mechanism of pore-fluid within the sediments. [Work supported by ONR Code 321OA and Kansai Power and Light Co.]
Mechanisms of action in dual-pulse lithotripsy
Authors: Sokolov Dahlia L. , Bailey Michael R. , Crum Lawrence A.
Published: October 2013

Dual-pulse lithotripsy has emerged as a promising technique for a safer and more effective shock wave lithotripsy treatment. A single source and confocal sources of various design have been used to produce either synchronous or asynchronous dual pulses. It has been shown that dual pulses enhance stone comminution and reduce tissue injury in vivo and in vitro. Pressure doubling at the focus of synchronous confocal sources contributes to increased fragmentation by a combination of direct shock-wave effects and increased cavitation, while decreased cell damage near the focus is largely a result of cavitation mitigation by the second, delayed shock wave. It follows that weaker pulses may be used to achieve complete stone fragmentation while further protecting surrounding tissue. Twin sources may also be fired asynchronously to enhance or mitigate cavitation as well as to minimize tissue damage by dividing the impact over two tissue paths. Numerical calculations using the Gilmore model and primary radiation force model as well as high speed camera images show little evidence that bubble translation contributes to the observed bioeffects. These results and the history and mechanisms of dual-pulse lithotripsy will be reported. [Work supported by NIH PO1 DK43881 and RO1 DK55674.]
Detection of buried mines with seismic sonar
Authors: Muir Thomas G. , Baker Steven R. , Gaghan Frederick E. , Fitzpatrick Sean M. , Hall Patrick W. , Sheetz Kraig E. , Guy Jeremie
Published: October 2013

Prior research on seismo-acoustic sonar for detection of buried targets [J. Acoust. Soc. Am. 103, 2333–2343 (1998)] has continued with examination of the target strengths of buried test targets as well as targets of interest, and has also examined detection and confirmatory classification of these, all using arrays of seismic sources and receivers as well as signal processing techniques to enhance target recognition. The target strengths of two test targets (one a steel gas bottle, the other an aluminum powder keg), buried in a sand beach, were examined as a function of internal mass load, to evaluate theory developed for seismic sonar target strength [J. Acoust. Soc. Am. 103, 2344–2353 (1998)]. The detection of buried naval and military targets of interest was achieved with an array of 7 shaker sources and 5, three-axis seismometers, at a range of 5 m. Vector polarization filtering was the main signal processing technique for detection. It capitalizes on the fact that the vertical and horizontal components in Rayleigh wave echoes are 90 deg out of phase, enabling complex variable processing to obtain the imaginary component of the signal power versus time, which is unique to Rayleigh waves. Gabor matrix processing of this signal component was the main technique used to determine whether the target was man-made or just a natural target in the environment. [Work sponsored by ONR.]
Acoustic landmine detection using binary maximum-length sequences
Authors: Xiang Ning , Sabatier James M.
Published: October 2013

Acoustic landmine detection using a LDV has demonstrated success in recent field tests [Sabatier and Xiang, IEEE Trans. Geosci. Remote Sens. 39, 1146–1154 (2001); Xiang and Sabatier, J. Acoust. Soc. Am. 113, 1333–1341 (2003)]. However, low detector signals and speckle noise are still challenging problems in the LDV-based acoustic-to-seismic detection of buried landmines. Scanning insonified patches over buried targets with the spatial resolution required in minefield applications demands processing of a large quantity of detection data. This work proposes the use of powerful signals-binary maximum-length sequences, as the acoustic excitation. By exploiting their excellent number-theory properties, high signal-to-noise ratios for the scanning results can be achieved. Furthermore, the fast maximum-length sequence transform is developed to allow the landmine detection algorithms to extract the impulse response of the acoustic-to-seismic soil / mine-soil system with efficient frequency-demodulation of the laser Doppler vibrometer signals. This presentation discusses some relevant issues associated with the detection system design and extensive field tests. [Work supported by U.S. Army CERDEC Night Vision and Electronic Sensors Directorate.]
A multi-carrier technique for ultrasonic Doppler vibrometry
Authors: Petculescu Andi , Sabatier James
Published: October 2013

A novel and simple technique for a signal-to-noise-ratio augmenting in ultrasonic Doppler vibrometry is presented. The approach involves sending two probe frequencies separated by twice the modulation frequency. By adjusting the mutual phase of the carriers, the overlapped sideband can be twice as large as the nonoverlapped ones. Moreover, the phase-demodulated signal is also larger than is obtained in the case of one-carrier operation. Parallel results of electronic phase modulation and ultrasonic Doppler vibrometry (with commensurate modulation strengths) are presented. A practical implementation of the method to probe vibrations of a rough surface is then described. [Work supported by ONR.]
Viscoelastic properties of laryngeal posturing muscles
Authors: Alipour Fariborz , Hunter Eric , Titze Ingo
Published: October 2013

Viscoelastic properties of canine laryngeal muscles were measured in a series of in vitro experiments. Laryngeal posturing that controls vocal fold length and adduction/abduction is an essential component of the voice production. The dynamics of posturing depends on the viscoelastic and physiological properties of the laryngeal muscles. The time-dependent and nonlinear behaviors of these tissues are also crucial in the voice production and pitch control theories. The lack of information on some of these muscles such as posterior cricoarytenoid muscle (PCA), lateral cricoarytenoid muscle (LCA), and intraarytenoid muscle (IA) was the major incentive for this study. Samples of PCA and LCA muscles were made from canine larynges and mounted on a dual-servo system (Ergometer) as described in our previous works. Two sets of experiments were conducted on each muscle, a 1-Hz stretch and release experiment that provides stress–strain data and a stress relaxation test. Data from these muscles were fitted to viscoelastic models and Young’s modulus and viscoelastic constants are obtained for each muscle. Preliminary data indicates that elastics properties of these muscles are similar to those of thyroarytenoid and cricothyroid muscles. The relaxation response of these muscles also shows some similarity to other laryngeal muscles in terms of time constants.
Logarithmic temporal axis manipulation and its application for measuring perceptually salient acoustic features of loudspeakers based on multiple observations
Authors: Morise Masanori , Kawahara Hideki
Published: October 2013

A new procedure for measuring impulse responses of loudspeakers in a real world situations were proposed, specifically aiming at extracting perceptually saliant features of the acoustic systems. The procedure consists of two stages. The first stage is an impulse response measurement using specially designed test signals (TSP or M-sequence). Post-processing using a logarithmic transformation of the temporal axis and filtering enables selective elimination of a time-frequency representation of the response that does not consists of components stimulated by the input signal. The second stage is to extract perceptual ‘‘variance’’ based on multi-location observations. The procedure was optimized to provide the best inverse filter in terms of the signal duration of the compensated response. Simulations were conducted to test general behavior of the proposed method. Preliminary tests using a robot controlled measuring stage demonstrated feasibility and effectiveness of the proposed method. [Work partly supported by the grant in aids in scientific research (B) 14380165 and Wakayama University.]
Estimation of acoustic signals in reverberant conditions via the characteristic function
Authors: Dat Tran H. , Fumitada Itakura
Published: October 2013

In many circumstances at reverberant conditions, acoustic signals are mixed by the multiple reflections and scattering phenomena. Recently the independent component analysis (ICA) has gained great advantages for processing this class of signals. Many implementations for both temporal and temporal-frequency, stationary and nonstationary, second order and high order statistics are given. However in these cases, the dynamic structure described by the changing of the time of sources number was not considered. In this paper first we proposed a generalized stochastic model allowing describing both a static and dynamic structure of sources. Then the joint characteristic function is analytically obtained. Second, we examine the estimation of an empirical characteristic function for given models.
Equalization of a one-dimensional sound field using acoustic energy density
Authors: Chen Xi , Leishman Timothy , Sommerfeldt Scott
Published: October 2013

For many years, reproduced and reinforced sound fields have been equalized using acoustic pressures measured at discrete field points. In this paper, well-known problems associated with this equalization method are investigated using a one-dimensional model. An optimum equalization scheme is then suggested that is based on the spatially averaged mean-square pressure of the field. A practical method based on the energy density of the field is subsequently discussed and compared to the other methods. Although the energy density is evaluated at a single field point, its spatial uniformity is shown to provide results approaching those of the optimum equalization method.
High frequency intensity fluctuations: Comparison of theory with experiment
Authors: Lutz Steven D. , Bradley David L. , Culver R. Lee
Published: October 2013

Amplitude fluctuations were measured during August 2002 near San Diego using 20 and 40 kHz cw and fm signals. Source–receiver separation was 1 km; source depths were 10 m to 67 m; receiver hydrophone depths were 44 m to 217 m. A 15-element chain of CTD sensors was towed to measure horizontal temperature and salinity variation with 1m resolution. Theory exists explaining the relationship between amplitude fluctuations and acoustic frequency, source–receiver separation, and index of refraction patch size in the ocean [e.g., Flatte et al., Sound Transmission Through a Fluctuating Ocean (Cambridge Press, 1979); Uscinsky et al., ‘‘Intensity Fluctuations. Part 1: Theory,’’ J. Acoust. Soc. Am. 74 (1983)]. However, the amplitude fluctuations we observe are much lower than that predicted by theory [J. Acoust. Soc. Am. 113, 2333 (2003)]. Our frequencies are 1 to 2 orders of magnitude higher than those used in the experiments upon which the theory is based and our propagation ranges are considerable shorter 1 km versus many km. Results will be discussed from a more detailed analysis of the ray path locations within the water column activity (Langmuir cell formation and internal wave passage).
Stone orientation affects the mechanism of failure in artificial kidney stones subject to shock waves
Authors: Van Cauwelaert Javier , Cleveland Robin O.
Published: October 2013

Micro computed tomography (CT) imaging was used to follow the progressive development of cracks in artificial kidney stones. The artificial stones were made from U30 cement with a cylindrical shape (6.5 mm diameter and 8.5 mm long). The stones were held within a polypropylene vial in one of three orientations: vertical, horizontal, and angled at 45 deg. The stones were treated with an electromagnetic lithotripter and the initiation and growth of cracks was observed using microCT. The images show that the orientation of the stones with respect to the shock changes the dominant mechanism for fragmentation. Vertical stones developed a spall-like crack near the distal surface, which propagated from the surface to the interior of the stone. Initiation of a secondary spall-like crack was observed proximal to the first crack. Little surface damage was observed. Horizontal stones presented pitting in the proximal surface and erosion in lateral faces, indicating the action of cavitation. Angled stones presented both spall-like fracture in either the leading or the distal corners and surface damage (pitting) in the proximal surface. Experiments are being performed to follow the development of cracks in human kidney stones. [Work supported by the Whitaker Foundation.]
Development and application of compact piezoelectric ESWT devices
Authors: Ginter Siegfried , Krau Werner , Bauer Edgar , Dreyer Thomas , Liebler Marko
Published: October 2013

The usage of shockwave devices permanently expands from initially lithotripsy to orthopedics and perhaps to drug-delivery in future applications. This demands more compact and cheaper but still powerful shockwave devices, which should generate reproducible sound fields and should be adjustable in some way to the special requirements of the therapy. Here several self-focusing piezoelectric transducers based on a double-layer piezo technology are presented. Sound field measurement results show that it is possible to obtain maximal peak pressure amplitudes from 58 to 132 MPa from small to medium sized sources with diameters of aperture ranging from 70 to 220 mm. The peak pressure amplitude and the amount of energy delivered to the focal region can be adjusted in a wide range. Clinical results demonstrate the therapeutic effectiveness for the treatment of orthopedic indications. These compact devices have the ability to meet the requirements of an extended range of therapeutic applications.
Target re-acquisition using acoustic features with an autonomous underwater vehicle-borne sonar
Authors: Edwards Joseph , Schmidt Henrik
Published: October 2013

Concurrent mapping and localization (CML) is a technique for unsupervised feature-based mapping of unknown environments, and is an essential tool for autonomous robots. For land robots, CML can be applied using video, laser, or acoustic sensors, while for autonomous underwater vehicles (AUVs) the only effective transducer in most situations is sonar. In the Generic Oceanographic Array Technology Sonar (GOATS) experiment series, CML was effectively demonstrated using a single AUV. A further hurdle in the full implementation of AUV minehunting is to re-acquire and identify targets of interest. Target re-acquisition allows other vehicles to be called into a target location to further investigate with adaptive sonar geometries or alternative sensor suites designed for classification. In this work, the features in the CML-generated map are extended from only spatial coordinates to include acoustic features such as spectral response. It is demonstrated that the inclusion of acoustic features aids in the global positioning within the map, although the fine positioning is still accomplished through standard CML. In addition, areas that are sparsely populated with targets, e.g., a sandy coastline, are shown to be more readily navigable using acoustic features.
Acoustic sensitivity analysis of optimal asset allocation for ASW
Authors: DelBalzo Donald R. , Rike Erik R.
Published: October 2013

In 1946, Koopman [Operations Evaluation Group Report 56, Navy Department] characterized optimal search for a stationary target in terms of arbitrary space-time effort density, with the searcher’s effectiveness defined by cumulative detection probability (given by the exponential search formula). Koopman’s solution maximizes target exposure at time t, given failure to detect at all previous times. This plan is myopic because it does not look into the future. In 1980, Brown [Operations Research 28, 1275–1289] generalized this result for a moving target. Brown’s algorithm allocates effort to maximize target exposure, given failure to detect by all prior and future search efforts. It converges to an optimal allocation, and typically converges rapidly because it simplifies sensor performance to a single factor (sweep rate in each cell), which eliminates the need for detailed sensor performance predictions. Experience has shown that sweep rate is an excellent predictor of search effectiveness, for high-level analyses. This work describes an approach to optimize several searchers simultaneously and investigates optimal asset allocation for coordinated, multiship missions under detailed conditions. The results show that attention to acoustic details can significantly increase overall search effectiveness, especially when using sensors with different capabilities. [Work sponsored by ONR.]
Echoview as a multibeam sonar data processing and analysis toolkit for fisheries research
Authors: Buelens Bart , Pauly Tim , Higginbottom Ian
Published: October 2013

Echoview is a hydroacoustic data analysis software package, widely used in the fisheries research and stock assessment communities. Originally developed to handle a variety of single-beam sonar data formats, Echoview has been extended to support multibeam data. Multibeam data logging, lossless compression, and real time beamforming and display are some of the software’s core features. Multibeam data has an additional dimension compared to single-beam data, and a 3D data viewer has been developed providing 3D visualizations of the seabed and fish schools detected by built-in algorithms. Since the multibeam module is just one of many software modules of the Echoview package, data from other sources such as single-beam sonar systems and current profilers can be combined and analyzed together with the multibeam data. The combination of coincident fish density estimates from calibrated single-beam backscatter data with school volume estimates from multibeam data will represent a significant improvement in stock assessment methods. Ongoing research and development will make it possible for Echoview to follow and even set new trends in multibeam water-column data analysis for fisheries research. Features under development include calibration, vessel motion compensation, improved feature detection, and enhanced and animated 3D displays.
Sound system coverage and intelligibility using AFR devices
Authors: Mapp Peter
Published: October 2013

AFR loudspeaker technology (audio full-range) combines the characteristics of distributed mode loudspeakers at mid and high frequencies with conventional loudspeaker piston action at low frequencies in a single driver. The combination retains the well-established advantages of the DML in respect of wide dispersion and improved interaction with reflective boundaries. A comparison study has been made using conventional 6-in. ceiling loudspeakers and AFR devices of comparable size in a typical open plan office situation. It is shown that the AFR devices exhibited noticeably improved coverage, clarity, and speech intelligibility. However, the use of traditional intelligibility measures, such as STI did not always reflect this subjectively observed trend. The use of STI or STIPa under high signal to noise conditions is questioned.
Performance comparison of above ceiling and through ceiling sound masking systems
Authors: Rosenberg Carl , Savereid Christopher , Horrall Thomas
Published: October 2013

Sound masking systems are an important tool for providing speech privacy in offices and similar spaces. These systems typically use an array of loudspeakers radiating masking sound above an acoustical tile ceiling. The ceiling acts to diffuse the sound laterally in order to minimize localization on loudspeakers by the listeners below. The diffusion also helps keep the speech-to-noise ratio relatively uniform spatially, which may help minimize variations in privacy conditions. Unfortunately, the ceiling material, the plenum, and the space below are rarely homogeneous acoustically. There are usually openings in the ceiling for HVAC return air and lighting fixture ventilation, and different parts of the ceiling often use a variety of materials and elevations for aesthetic reasons. Large ducts and structural elements may compartmentalize the plenum. These variations pose substantial acoustical challenges for the designer and additional costs for the owner, not all of which can be satisfactorily resolved. Recognizing these issues, several manufacturers have recently introduced masking systems that might be characterized as direct field systems. These systems use masking loudspeakers that radiate directly into the occupied space rather than into a plenum. This paper contrasts the typical performance and other characteristics of the two basic types of systems.
Development of a sea-well facility for calibrating multibeam sonar
Authors: Foote Kenneth G. , Hammar Terence R. , Liberatore Stephen P. , Doherty Kenneth W.
Published: October 2013

In order to calibrate multibeam sonars for use in quantifying water-column backscattering, a sea-well facility has been developed on Iselin Dock at the Woods Hole Oceanographic Institution. The suite of equipment and calibration instruments is described. This includes systems for mounting and rotating transducer arrays, a number of precision targets, systems for target suspension and positioning, and an external sonar-triggering unit. [Work supported by NSF Grant No. OCE-0002664.]
Estimating reverberation time in classrooms by the power method
Authors: Godfrey Richard D.
Published: October 2013

The Sabin equation relates reverberation time to room volume and absorption. If an acoustic source of known power is placed in a room, the absorption is also related to the power per bandwidth, volume, and pressure. Combining the Sabin equation with the power equation and solving for reverberation time yields a relationship for reverberation time as a function of volume, pressure, and the power of the source. This approach has been reported to deviate from the decay method at low frequency. In a laboratory reverberation room, it yielded reasonable results in the frequency range of interest in classrooms. Reasonable results were also achieved in real classrooms in the 500- to 2000-Hz frequency range. Based on these findings, it may be possible to make acceptable reverberation time measurements in less time with less sophisticated instrumentation than the decay method.
Parameters affecting the detection of microbubbles in blood
Authors: Coussios Constantin-C. , Zanetti Paolo , Roy Ronald A.
Published: October 2013

The ability to detect small gas bubbles in blood depends on the relative magnitude of the acoustic power backscattered from the microbubbles (‘‘signal’’) to the power backscattered from the red blood cells (‘‘noise’’). Erythrocytes are weak, Rayleigh scatterers, and therefore the backscattering coefficient (BSC) of blood increases as the fourth power of frequency throughout the diagnostic frequency range. Microbubbles, on the other hand, are either resonant or super-resonant in the range 10–30 MHz. Above resonance, their total scattering cross-section remains constant with increasing frequency and the directivity pattern of the scattered wave changes significantly. Therefore, increasing the detection frequency may lead to a reduction in signal-to-noise ratio. An active cavitation detector (ACD) was utilized to observe the gradual obscuring of a steel target in blood with increasing frequency, and to measure the BSC of suspensions of Optison® microspheres in blood, as a function of microsphere concentration, hematocrit and frequency in the range 10–30 MHz. The experimental results were compared with theoretical predictions of the BSC of Optison® and blood, in order to determine whether the presence of tightly packed red blood cells affects the acoustic response of the microbubbles. [Work supported by the ASA, the US Army, and the NSF.]
Whistle suppression at a duct–sidebranch interface by boundary layer perturbation
Authors: Madden Andrew , Selamet Ahmet , Tallio Kevin V.
Published: October 2013

Whistles are generated when shear layer instabilities in a main duct couple with acoustic resonances in a sidebranch. Such flow-acoustic coupling phenomenon is suppressed by perturbing, thus thickening the boundary layer near the interface of the adjoining ducts in an experimental setup, consisting of a closed sidebranch connected to a main duct. The boundary layer is perturbed by inserting pins that protrude into the main duct immediately upstream of the sidebranch duct. The pin height, diameter, and spacing are varied. The sound pressure is measured at the inlet of the main duct using a sound level meter, followed by a spectral analysis to determine the whistle frequencies. Pressure is also measured at the end of the sidebranch by a piezoelectric transducer to quantify the resonant amplitudes. The large-magnitude whistles produced by flow-acoustic coupling are suppressed in nearly all cases by the use of pins which provide, at times, more than 10 dB reduction at peak amplitudes. Furthermore, the introduction of pins into the main flow does not increase the background noise in the duct.
Interaction of pipe tone and edge tone in organ pipe oscillation
Authors: Nolle A. W.
Published: October 2013

Inharmonic partials in an organ pipe tone can occur in clusters, at uniform frequency separation. The primary object of this discussion is to demonstrate that these clusters arise in a nonlinear process: Edge tone oscillation is modulated at the fundamental frequency of the pipe tone. The mechanism is demonstrated by a laboratory analog, in which periodic deflection of a jet producing an edge tone is forced by a transverse acoustic flow, and also by a numerical analog. Additional examples show that the simultaneous occurrence of a pipe tone and an unmodulated edge tone can occur at low amplitudes of oscillation, where the nonlinear interaction is unimportant.
Heat transfer of heat exchangers in a standing wave thermoacoustic cooler
Authors: Paek Insu , Braun James E. , Mongeau Luc
Published: October 2013

Standing wave thermoacoustic coolers require heat exchangers to move heat in and out of the working gas. Within most finned-tube type heat exchangers, heat is transferred from the oscillating gas to a liquid flowing through the tubes. Experiments were performed to evaluate the thermal performance of heat exchangers immersed in a standing wave thermoacoustic cooler. The gas-side convection heat transfer coefficient was calculated from the measured data, and compared to steady flow heat transfer model predictions. A simple relation between the Reynolds number in steady flow and the time dependent acoustic Reynolds number was obtained. The results suggest that substituting this relation into known steady flow correlations may yield accurate predictions of the heat transfer coefficient in oscillating flow.
Minor losses in high-amplitude acoustic resonators with varying changes in cross section
Authors: Doller Andrew J. , Atchley Anthony A.
Published: October 2013

In a previous paper [J. Acoust. Soc. Am. 112 (2003)], measurements of time-averaged pressure at the closed end of a high-amplitude resonator having a non-uniform cross section were presented. The motivation for this continued work is to better understand minor losses in high-amplitude oscillatory flows through changes in resonator cross section. The resonators consist of two sections of straight brass pipe of different diameters and joined through either step-like or conical couplers. They are driven at the end of the large diameter pipe with a rigid piston. The end of the small tube is rigidly terminated. In the current paper, data obtained from an improved experimental apparatus will be presented. The improvements consist of better temperature control and the ability to measure the power delivered to the resonator by the piston. Subtraction of the linear acoustic boundary-layer losses from the measured input power provides an upper estimate on the power dissipated through other mechanisms. The dependence of the time-averaged pressure and power dissipation on drive amplitude, junction type, and junction location in the standing wave will be discussed. [Research supported by ONR.]
System identification and energy-based active noise control performance
Authors: Faber Benjamin M. , Sommerfeldt Scott D.
Published: October 2013

An active noise control system, which minimizes acoustic energy density, can often become unstable due to significant changes in the acoustical environment in which it operates. Typically, the control system of interest, which is based on a modified version of the filtered-x LMS algorithm, is operated with a fixed set of system identification filter coefficients. These coefficients are determined off-line, prior to execution of the main control algorithm. The performance of the control system depends on the quality of the system model obtained through the system identification algorithm. Changes in the system transfer function and impulse response, due to various factors, including temperature, boundary conditions, and sensor/actuator location, have been investigated. Results will be presented, which give indications regarding what types of changes to the system have the greatest effect on the transfer function and impulse response, and how sensitive the control system is to those effects. The effects of changing sampling rates and system identification filter lengths on the quality of the system model have also been investigated and will be discussed.
Acoustic control in a tractor cabin using two optimally designed Helmholtz resonators
Authors: Driesch Patricia L. , Koopmann Gary H.
Published: October 2013

A virtual design methodology is developed to minimize the noise in enclosures with optimally designed, passive, 20 acoustic absorbers (Helmholtz resonators). A series expansion of eigenfunctions is used to represent the acoustic=20 absorbers as external volume velocities, eliminating the need for a solution of large matrix eigenvalue problems. A determination of this type (efficient model/reevaluation approach) significantly increases the design possibilities when optimization techniques are implemented. As a full-scale demonstration, the acoustic response from 90–190 Hz of a tractor cabin was investigated. The lowest cabin mode proposes a significant challenge to a noise control engineer since its anti-node is located near the head of the operator and often generates unacceptable sound-pressure levels. Exploiting the low-frequency capability of Helmholtz resonators, lumped parameter models of these resonators were coupled to the enclosure via an experimentally determined acoustic model of the tractor cabin. The virtual design methodology uses gradient optimization techniques as a post-processor for the modeling and analysis of the unmodified acoustic interior to determine optimal resonator characteristics. Using two optimally designed Helmholtz resonators, potential energy was experimentally reduced by 3.4 and 10.3 dB at 117 and 167 Hz, respectively.
Acoustic signature of an AUV
Authors: Cuschieri Joe , Frandsen Susan
Published: October 2013

In this presentation further results from an experimental analysis of the acoustic signature of an Ocean Explorer class AUV are presented. The results to be presented include, data collected in an open water environment with the AUV operating at cruising speed, measurements performed in a reverberant test tank on an AUV model, and measurements in the reverberant test tank of an AUV under typical operating conditions. Different operating conditions and different mountings for the main propulsion and control module (podule) inside the AUV are considered. Inside the podule are the propulsion motor and the motors for the control surfaces with penetrations for the main propulsion shaft and the shafts for the control surfaces. Considered in the measurements is the influence of the propeller, the mounting of the podule, and the covering the podule with a compliant layer. It is shown that for the type of AUV considered here, the type of mounting of the podule is not very significant and that significant energy is transferred through the water trapped in between the podule and the AUV hull. Furthermore, the propeller has a significant influence on the acoustic signature.
Computational and experimental techniques for structural acoustics
Authors: Walsh Timothy F. , Sumali Hartono , Dohner Jeffrey L.
Published: October 2013

In this paper a discussion of various computational and experimental methods under development at Sandia for evaluating structural acoustic interactions will be presented. The driving applications range from the microscale to the macroscale. An overview will be given of Salinas, a massively parallel structural dynamics code that has been developed at Sandia, and its embedded structural acoustic capabilities. Salinas can perform coupled structural acoustic simulations of the interior and exterior of large-scale structures as well as Micro-Electro-Mechanical Systems (MEMS). An ongoing research effort in Salinas for including viscosity in the acoustic computations will be discussed. Viscosity is typically ignored in commercial acoustics codes. From the experimental side an acoustic wave tube will be described, which is to be used for validating structural acoustic computations and other acoustic experiments of interest. Also, acoustic experimental facilities for MEMS applications will be described. [Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy’s National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.]
Computer methods in vibrational ecology problems
Authors: Rybak Samuil A. , Makhortykh Sergey A. , Kostarev Stanislav A. , Gatina Aleksandra R.
Published: October 2013

In the paper formulations of direct vibrational ecology problems are described. Linearly spaced source of acoustic waves in the solid media is considered (e.g., tunnel in soil, simulated by the thin elastic shell). In this case the shell is exited by the inner force changing in time and spatial variables. The proposed computer prognosis method is realized in VibLab software of the Russian Tunneling Association for two versions of algorithms: in homogeneous and stratified two-dimensional media. Three general stratification types are considered: two waveguides (subsurface and waveguide with the axis on the depth H) and stratification with linearly increased wave speed. On the basis of these approximations the amendments, respectively, liquid soil case were calculated. A vibrational field in the ground is described by cylinder waves; modulation of this field type is assessed by a simple final elements scheme. The aspects of application of the proposed algorithms in inverse problems of media parameters determined are also discussed in the report. [Work supported by the Russian Foundation for Basic Research Grants No. 01-02-16127 and No. 02-02-17143.]