bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical prediction of break-out noise from a reactive rectangular plenum with four flexible walls
Authors: Venkatesham B. , Tiwari Mayank , Munjal M. L.
Published: October 2010

This paper describes an analytical calculation of break-out noise from a rectangular plenum with four flexible walls by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The breakout noise from rectangular plenums is important and the coupling between acoustic waves within the plenum and structural waves in the flexible plenum walls plays a critical role in prediction of the transverse transmission loss. The first step in breakout noise prediction is to calculate the inside plenum pressure field and the normal flexible plenum wall vibration by using an impedance-mobility approach, which results in a compact matrix formulation. In the impedance-mobility compact matrix (IMCM) approach, it is presumed that the coupled response can be described in terms of finite sets of the uncoupled acoustic subsystem and the structural subsystem. The flexible walls of the plenum are modeled as an unfolded plate to calculate natural frequencies and mode shapes of the uncoupled structural subsystem. The second step is to calculate the radiated sound power from the flexible walls using Kirchhoff–Helmholtz (KH) integral formulation. Analytical results are validated with finite element and boundary element (FEM-BEM) numerical models.
Longitudinal changes in hearing sensitivity among men: The Veterans Affairs Normative Aging Study
Authors: Echt Katharina V. , Smith Sherri L. , Burridge Andrea Backscheider , Spiro Avron
Published: October 2010

Over 35 years (1962–1996), participants of the Veterans Affairs Normative Aging Study (NAS), a study of healthy aging in men, completed up to eight audiometric assessments. This report describes the age-related hearing trajectories of screened men (n=953) aged 23 to 81 years at enrollment, estimates the typical rate of change per decade in hearing sensitivity, and compares longitudinal and cross-sectional estimates of change in hearing sensitivity. The men were followed 14 years on average. The hearing trajectories, based on a mixed-effects model analytical approach to the data, provide converging evidence that hearing loss in aging is pervasive and progressive even among men initially selected for good physical health. Typically the men accrued early losses (>25 dB HL) in hearing sensitivity at the higher frequencies beginning in the early 40s, but maintained hearing thresholds better than 25 dB HL for lower frequencies into old age. The average rate of change per year across frequencies and age was 0.69 dB. Predicted cross-sectional estimates of change in hearing sensitivity reliably approximated longitudinal trajectories, with slight misestimations in the 8th decade.
Swept-tone transient-evoked otoacoustic emissions
Authors: Bennett Christopher L. , Özdamar Özcan
Published: October 2010

Transient-evoked otoacoustic emissions (TEOAE) are responses generated within the inner ear in response to acoustic stimuli and are indicative of normal cochlear function. They are commonly acquired by averaging post-stimulus acoustic responses recorded near the eardrum in response to brief stimuli such as clicks or tone pips. In this study a new long duration stimulus consisting of a frequency swept tone is introduced for the acquisition of TEOAEs. Like stimulus frequency generated OAEs, swept-tone responses contain embedded OAEs. With swept-tone analysis, OAEs can be recovered by convolving it with a time reversed swept-tone signal resulting in time-compression. In addition, higher order nonlinear OAE responses were removed from the linear TEOAE. The results show comparable phase and time-frequency properties between the click and swept-tone evoked OAEs. Swept-tone acquisition of TEOAEs has beneficial noise properties, improving the signal to noise ratio by 6 dB compared to click evoked responses thus offering testing time savings. Additionally, swept-tone analysis removed synchronized spontaneous OAE activity from the recordings of subjects exhibiting such responses in conventional click TEOAEs. Since swept-tone stimulus consists of a single frequency component at any instantaneous moment, its analysis also provides for direct comparison with stimulus-frequency OAEs and click evoked OAEs.
Microstructure based model for sound absorption predictions of perforated closed-cell metallic foams
Authors: Chevillotte Fabien , Perrot Camille , Panneton Raymond
Published: October 2010

Closed-cell metallic foams are known for their rigidity, lightness, thermal conductivity as well as their low production cost compared to open-cell metallic foams. However, they are also poor sound absorbers. Similarly to a rigid solid, a method to enhance their sound absorption is to perforate them. This method has shown good preliminary results but has not yet been analyzed from a microstructure point of view. The objective of this work is to better understand how perforations interact with closed-cell foam microstructure and how it modifies the sound absorption of the foam. A simple two-dimensional microstructural model of the perforated closed-cell metallic foam is presented and numerically solved. A rough three-dimensional conversion of the two-dimensional results is proposed. The results obtained with the calculation method show that the perforated closed-cell foam behaves similarly to a perforated solid; however, its sound absorption is modulated by the foam microstructure, and most particularly by the diameters of both perforation and pore. A comparison with measurements demonstrates that the proposed calculation method yields realistic trends. Some design guides are also proposed.
Quantitative estimation of minor conductive hearing loss with distortion product otoacoustic emissions in the guinea pig
Authors: Olzowy Bernhard , Deppe Christoph , Arpornchayanon Warangkana , Canis Martin , Strieth Sebastian , Kummer Peter
Published: October 2010

Subclinical conductive hearing losses (CHLs) can affect otoacoustic emissions and therefore limit their potential in the assessment of the cochlear function. Theoretical considerations to estimate a minor CHL from DPOAE measurements [Kummer et al. (2006). HNO 54, 457–467] are evaluated experimentally. They are based on the fact, that the level difference of the stimulus tones L1 and L2 for optimal excitation of the inner ear is given by L1=aL2+b. A CHL is presumed to attenuate both L1 and L2 to the same extent such that excitation of the inner ear is no longer optimal. From the change of L1 that is necessary to restore optimal excitation of the inner ear and thus to produce maximal DPOAE levels, the CHL can be estimated. In 10 guinea pig ears an experimental CHL was produced, quantified by determination of compound action potential (CAP) thresholds at 8 kHz (CHLCAP) and estimated from DPOAE measurements at 8 kHz (CHLDPOAE). CHLs up to 12 dB could be assessed. CHLDPOAE correlated well with CHLCAP (R=0.741, p=0.0142). Mean difference between CHLDPOAE and CHLCAP was 4.2±2.6 dB. Estimation of minor CHL from DPOAE measurements might help to increase the diagnostic value of DPOAEs.
Does fundamental-frequency discrimination measure virtual pitch discrimination?
Authors: Micheyl Christophe , Divis Kristin , Wrobleski David M. , Oxenham Andrew J.
Published: October 2010

Studies of pitch perception often involve measuring difference limens for complex tones (DLCs) that differ in fundamental frequency (F0). These measures are thought to reflect F0 discrimination and to provide an indirect measure of subjective pitch strength. However, in many situations discrimination may be based on cues other than the pitch or the F0, such as differences in the frequencies of individual components or timbre (brightness). Here, DLCs were measured for harmonic and inharmonic tones under various conditions, including a randomized or fixed lowest harmonic number, with and without feedback. The inharmonic tones were produced by shifting the frequencies of all harmonics upwards by 6.25%, 12.5%, or 25% of F0. It was hypothesized that, if DLCs reflect residue-pitch discrimination, these frequency-shifted tones, which produced a weaker and more ambiguous pitch than would yield larger DLCs than the harmonic tones. However, if DLCs reflect comparisons of component pitches, or timbre, they should not be systematically influenced by frequency shifting. The results showed larger DLCs and more scattered pitch matches for inharmonic than for harmonic complexes, confirming that the inharmonic tones produced a less consistent pitch than the harmonic tones, and consistent with the idea that DLCs reflect F0 pitch discrimination.
Stability of the parametrically excited damped inverted pendulum: Theory and experiment
Authors: Carbo Randy M. , Smith Robert W. M. , Poese Matthew E.
Published: October 2010

The parametrically driven, damped, inverted pendulum can be dynamically stabilized in particular regions of the parameter space. The impact of damping on dynamic stabilization can be stabilizing or destabilizing depending on the location in parameter space (i.e., drive frequency and amplitude). Floquet analysis and numerical simulations were used to determine the stable regions. An experiment was conducted that verifies the model. Physical explanations and simple bounding approximations are provided to summarize findings. The utility of the highly damped pendulum results are illustrated by drawing the analogy to dynamic stabilization of the Rayleigh-Taylor instability: it permits ready demonstration that dynamic stabilization is impossible in that system absent surface tension.
Relative contribution of off- and on-frequency spectral components of background noise to the masking of unprocessed and vocoded speech
Authors: Apoux Frédéric , Healy Eric W.
Published: October 2010

The present study examined the relative influence of the off- and on-frequency spectral components of modulated and unmodulated maskers on consonant recognition. Stimuli were divided into 30 contiguous equivalent rectangular bandwidths. The temporal fine structure (TFS) in each “target” band was either left intact or replaced with tones using vocoder processing. Recognition scores for 10, 15 and 20 target bands randomly located in frequency were obtained in quiet and in the presence of all 30 masker bands, only the off-frequency masker bands, or only the on-frequency masker bands. The amount of masking produced by the on-frequency bands was generally comparable to that produced by the broadband masker. However, the difference between these two conditions was often significant, indicating an influence of the off-frequency masker bands, likely through modulation interference or spectral restoration. Although vocoder processing systematically lead to poorer consonant recognition scores, the deficit observed in noise could often be attributed to that observed in quiet. These data indicate that (i) speech recognition is affected by the off-frequency components of the background and (ii) the nature of the target TFS does not systematically affect speech recognition in noise, especially when energetic masking and/or the number of target bands is limited.
Decentralized control of sound radiation using iterative loop recovery
Authors: Schiller Noah H. , Cabell Randolph H. , Fuller Chris R.
Published: October 2010

A decentralized model-based control strategy is designed to reduce low-frequency sound radiation from periodically stiffened panels. While decentralized control systems tend to be scalable, performance can be limited due to modeling error introduced by the unmodeled interaction between neighboring control units. Since bounds on modeling error are not known in advance, it is difficult to ensure the decentralized control system will be robust without making the controller overly conservative. Therefore an iterative approach is suggested, which utilizes frequency-shaped loop recovery. The approach accounts for modeling error introduced by neighboring control loops, requires no communication between subsystems, and is relatively simple. The control strategy is evaluated numerically using a model of a stiffened aluminum panel that is representative of the sidewall of an aircraft. Simulations demonstrate that the iterative approach can achieve significant reductions in radiated sound power from the stiffened panel without destabilizing neighboring control units.
Relative contribution to speech intelligibility of different envelope modulation rates within the speech dynamic range
Authors: Stone Michael A. , Füllgrabe Christian , Moore Brian C. J.
Published: October 2010

The contribution of envelope cues at different rates to intelligibility in a competing-speech task was measured as a function of the short-term envelope level. The target and background mixture was processed using tone vocoders. Envelope signals for each vocoder channel were simultaneously extracted with two low-pass filters, the cutoff frequency of one filter (L) being two octaves below that of the other (H). The envelope from the H filter was used at the peaks and that from the L filter at valleys, or vice versa. This was achieved by cross-fading between the two envelope signals based on a “switching threshold” that was parametrically varied relative to the long-term RMS level of the channel signal. When the cutoff frequencies of the H and L filters were 50 and 12.5 Hz, changes in speech intelligibility occurred mainly when the switching threshold was between −18 and +10 dB. The range was slightly narrower when the cutoff frequencies of the H and L filters were 200 and 50 Hz. Intensity-importance functions for higher-rate envelope modulations suggested that levels ranging from 20 dB below to about 10 dB above the channel RMS level were important, with maximum importance for levels around −5 dB.
Overshoot using very short signal delays
Authors: McFadden Dennis , Walsh Kyle P. , Pasanen Edward G. , Grenwelge Erin M.
Published: October 2010

The detectability of a 10-ms tone masked by a 400-ms wideband noise was measured as a function of the delay in the onset of the tone compared to the onset of the noise burst. Unlike most studies like this on auditory overshoot, special attention was given to signal delays between 0 and 45 ms. Nine well-practiced subjects were tested using an adaptive psychophysical procedure in which the level of the masking noise was adjusted to estimate 79% correct detections. Tones of both 3.0 and 4.0 kHz, at different levels, were used as signals. For the subjects showing overshoot, detectability remained approximately constant for at least 20–30 ms of signal delay, and then detectability began to improve gradually toward its maximum at about 150–200 ms. That is, there was a “hesitation” prior to detectability beginning to improve, and the duration of this hesitation was similar to that seen in physiological measurements of the medial olivocochlear (MOC) system. This result provides further support for the hypothesis that the MOC efferent system makes a major contribution to overshoot in simultaneous masking.
Cancellation of spurious arrivals in Green’s function retrieval of multiple scattered waves
Authors: Snieder Roel , Fleury Clement
Published: October 2010

The Green’s function for wave propagation can be extracted by cross-correlating field fluctuations excited on a closed surface that surrounds the employed receivers. This study treats an acoustic multiple scattering medium with discrete scatterers and shows that for a given source the cross-correlation of waves propagating along most combinations of scattering paths gives unphysical arrivals. Because theory predicts that the true Green’s function is retrieved, such unphysical arrivals must cancel after integration over all sources. This cancellation occurs because the scattering amplitude of each scatterer satisfies the generalized optical theorem. The cross-correlation of scattered waves with themselves does not lead to the correct retrieval of scattered waves, because the cross-terms between the direct and scattered waves is essential.
Trends in contemporary theater design: Arup Acoustics.
Authors: Myrbeck Shane , Deuchars Angus , Crowe Ned
Published: October 2010

This presentation will describe the design process for a quartet of drama theaters completed by Arup Acoustics over the past decade. While the theaters addressed include both US and UK facilities, in this paper we will largely focus on the two US venues: The Las Vegas Academy Theater and the Tempe Center for the Arts. Along with the discussion regarding the room acoustics aspects of geometry, finish materials, and sound isolation, the integration of electroacoustic enhancement systems to provide acoustic variability will also be described. This presentation is being given in association with the publication of an ASA book on the subject of drama theaters, which will include the facilities mentioned here.
New theaters built in Brazil.
Authors: Nepomuceno José
Published: October 2010

In the past 15 years new theaters have been designed in Brazil based on acoustical and theatrical concepts. Teatro de Paulínia and Teatro Bradesco were selected to represent this group. Teatro de Paulínia is a multipurpose theater seating 1330. The program includes popular music, opera, movie film, dance, musical, drama, and concerts. A concert shell is installed in the stage for orchestra presentations. Opened on 2008 the theater is very well received by musicians, actors, and the critics. Teatro Bradesco, was opened in 2009 and seats 1457. It is a multiuse venue for drama, dance, popular music, and musicals. The space was designed with theater and acoustics on top of design decisions, and as a result, since the opening night, is receiving excellent reviews from critics and users. The venue is built in a shopping mall and sound isolation measures were taken to minimize sound transmissions from adjacent facilities. The theater is surrounded by acoustical joints and built on bearing rubber pads. There are 76 pads with load capacity ranging from 20 to 1600 tons depending on the column. The paper will present their acoustical characteristics, models, tested parameters, and commissioning phase observations. Other theaters will be presented also.
Above and below: Acoustical challenges of theater fly-towers and displacement plena.
Authors: O’Keefe John
Published: October 2010

The Esplanade Arts and Heritage Centre is located in Medicine Hat, Alberta. It includes a 700 seat proscenium arch theater and a 150 seat studio theater. The larger room is a multi-purpose space that must serve the acoustical requirements of theater and symphonic music. The latter requirement dictated a taller room than the design architect preferred. An “acoustically transparent” ceiling was proposed which, in turn, prompted a physical scale model study; the limitations of computer modeling being inappropriate for this task. Small scale model auralization techniques were developed and played a key role in determining how much sound migrates into the fly-tower through a partially open orchestra shell. It turns out that computer models had dramatically over-estimated the propagation of sound through the shell, resulting in dangerously low predictions of early decay time. New design and analysis algorithms were also developed to predict and quantify the noise control properties of the building’s HVAC displacement system plenum. The project, or more specifically the project’s technological innovations, were recognized with The Schreyer Award, Canada’s highest distinction for engineering.
The “theater inside-out” and other spaces.
Authors: Kahle Eckhard , Jurkiewicz Yann , Wulfrank Thomas
Published: October 2010

Over the last years, Kahle Acoustics has had the opportunity to collaborate on several projects for innovative theatrical spaces. For The Curve in Leicester, UK, from the start of the design process the brief called for what was labeled the “theater inside-out,” a theater that would be visible from the street and breaks with the classical boundaries between front of house and back of house spaces. In the final design, the central stage opens onto both a 750-seat auditorium on one side and a 350-seat Black Box theater on the other side. In addition, the side walls of the stage house are vertically moving acoustic shutters, so that the stage can be opened to the glass-clad foyer surrounding the theaters. Other spaces include the more classical Royal Flemish Theatre (KVS) in Brussels and the Thâtre de l’Archipel in Perpignan, a theater with two configurations and variable seat count from 600 to 1100, and the highly flexible space La Commanderie in Dole, France, with variable seat count from 592 to 2700, and usage ranging from intimate theater to opera, classical concerts, as well as professional sports events and standing audience rock concerts.
The use of acoustic monitoring in the National Marine Fisheries Service marine mammal incidental take authorizations.
Authors: Guan Shane , Harrison Jolie
Published: October 2010

Under the Marine Mammal Protection Act (MMPA), the National Marine Fisheries Service (NMFS) is charged with conservation and management of marine mammals under NMFS’ jurisdiction. A regulatory mechanism is in place for NMFS to issue incidental take authorizations under the MMPA to operators whose activities may adversely affect marine mammals. As a mandate under the MMPA, mitigation and monitoring measures are prescribed to minimize any impacts on marine mammals and their habitat (prey species and acoustic environment) and to assess the degree of such impacts when such incidental take authorizations are issued. However, due to the limited visual range under and above water, monitoring measures using acoustical techniques are often required to supplement visual monitoring and to assist in making mitigation decisions. This presentation provides a summary of existing acoustic monitoring measures that are currently used in NMFS’ marine mammal incidental take authorizations; discusses the limitations, technical issues, practicality, and training needs involving acoustic monitoring; and highlights future needs in standardizing, improving, and expanding such techniques for more effective mitigation and monitoring measures.
Does environmental noise really affect reef fish behavior or are they talking while we cannot listen to them?
Authors: Rivera Chavarria Mario
Published: October 2010

Although it has been hypothesized that reef fish reduces sound production during extreme environmental events, it is possible that fish sounds are still present but only masked by elevated environmental noise. Although available acoustic technology makes it difficult to address this question, we can still generate hypotheses about the impact of environmental noise on fish sound production. Is there a behavioral response to environmental noise, or are fish sounds present at the same levels but masked and therefore undetectable without adequate filters? We recorded sciaenid (Pisces: Sciaenidae) sound production around Isla Tortuga, Costa Rica, during the “Nortes,” a period of strong winds caused by cold fronts and extreme variation of atmospheric pressure. Sciaenid sounds apparently stopped with almost no emissions during strong winds (56 miles/h) and transitioned to the normal emission rate on the next day when winds receded to 2 miles/h. We hypothesize that fish sounds were present at all times, but masked by wind-produced noise instead of a biological modulation as described by Mann and Grothues (2009) in similar conditions. I present circumstantial evidence in support of this hypothesis and discuss possible methods to test it directly.
Low-frequency sound scattering from microbubble distributions.
Authors: Carey William M. , Roy Ronald A.
Published: October 2010

Backscatter from the sea surface is governed by the roughness of the surface and subsurface micro bubble distributions. At low frequencies, due to the paucity of large bubbles, scattering results primarily from coherent and/or collective scatter from bubbles entrained by the subsurface vorticity or carried to depth by the Langmuir circulation and thermal convection. Theoretical treatments using the work of Mallock and Wood show that scattering from compact regions is a function of the volume fraction of air and to first order can be described by a Minnaert formula modified with the volume fraction. Experiments to test this theory were conducted in a lake and large tank facility. Back scattering from a submerged bubble cloud produced results consistent with our theory when parameters independently measured, such as bubble size distribution, volume fraction, and the cloud size, were used to calculate the resonant frequency with the modified Minnaert formula. This theory was further tested by backscattering experiments on bubbly liquid filled tubes, bubbly gel filled cylinders, and voided polyurethane spheres. Again the resonant frequency and backscatter measurements were found consistent with theoretical expectations; however, the effective dampening was found to depend on the nature of the material containing the microbubbles.
Low-frequency acoustical interactions and scattering from schools of swim bladder fish.
Authors: Feuillade Christopher
Published: October 2010

Low-frequency acoustic scattering from swim bladder fish is dominated by the bladder resonance response. Dense schools of these fish frequently consist of individuals of similar size, arranging themselves about one fish length apart. At near-resonance frequencies, acoustical interactions between the fish can cause the ensemble behavior of the school to become highly complex. Multiple scattering between neighboring fish affects the wave field of each individual. Additionally, since the wavelength at resonance is generally many times the fish spacing, the scattered fields interact coherently. Both features must also be incorporated to realistically describe scattering from fish schools. An effective methodology is available through the application of self-consistent multiple scattering techniques. The mathematical formalism used is based upon the solution of sets of coupled differential equations and incorporates a verified swim bladder scattering kernel for an individual fish. All orders of multiple scattering interactions between the fish are included, and the aggregate scattering field is calculated by coherent summation. Application to groups of closely spaced fish indicates significant deviations from the returns expected when incoherent scattering is dominant. The approach promotes an improved understanding of the ensemble physical properties of, as well as backscattering from, schools of swim bladder fish.
Acoustic estimates of size distribution for bubbles released from the seabed.
Authors: Weber Thomas C. , Williams Kevin L. , Tang Dajun
Published: October 2010

Bubbles rising from the seabed evolve as they rise through the water column due to gas transfer and changes in hydrostatic pressure. Consequently, the bubble’s acoustic response can change quite dramatically as it rises. For depth integrated measurements of target strength from these bubble clouds, depth dependent changes can confound acoustic inversions for bubble size distribution, void fraction, and the amount of bubbles (and hence gas) reaching the ocean surface. One approach to solving this problem is to implement a model for the evolution of the bubble as it rises through the surface and to then compute an effective, depth integrated scattering response for the bubble plume as a function of bubble size at the source. This effective scattering strength can then be used for inversions of frequency dependent, depth integrated target strength measurements to find the source distribution of bubbles. Such an inversion procedure has been implemented using an incoherent forward model, and tested for a steady stream of bubbles pumped through an orifice at a depth of 11 m. Broadband (1–30 kHz) target strength estimates were made at a distance of approximately 10 m. Inversions for the source distributions of bubbles are compared with estimates made directly with underwater video. Results of this acoustic inversion, and possible coherent bubble cloud effects, will be discussed.
Attenuation of low-frequency underwater sound using bubble resonance phenomena and acoustic impedance mismatching.
Authors: Lee Kevin M. , Hinojosa Kevin T. , Wochner Mark S. , Argo Theodore F. , Wilson Preston S. , Mercier Richard S.
Published: October 2010

Air bubbles can be a significant source of attenuation in underwater sound propagation, but such effects have not been experimentally verified for low frequencies in part due to the difficulty in creating large stable bubbles. This work is in part an extension of a previously reported study on the acoustic effects of large resonant encapsulated air bubbles in a 1-D waveguide [J. Acoust. Soc. Am. 127, 2015 (2010)]. Now, both bubble resonance effects and impedance contrast effects are investigated in a large (2600 m3) tank. Both of these mechanisms are shown to attenuate sound at low frequencies (50–200 Hz) through experiments in which a sound source is surrounded by a column of freely rising sub-resonant bubbles, a matrix of tethered resonant air balloons, and a combination of the two. Experiments with a matrix of thicker-shelled encapsulated bubbles demonstrate decreased attenuation due to weaker resonant interaction. The use of a polydipserse versus monodisperse encapsulated bubble size distribution demonstrates a flattened frequency response for fixed global void fraction. Finite-element models of both an effective medium bubble cloud and discrete stationary bubbles are discussed and compared with experiment. [Work supported by Shell.]
Effects of multiple scattering, attenuation, and dispersion on fish population density imaging with ocean-acoustic waveguide remote sensing.
Authors: Andrews Mark , Gong Zheng , Ratilal Purnima
Published: October 2010

Ocean-acoustic waveguide remote sensing (OAWRS) instantaneously images and continuously monitors fish populations distributed over continental-shelf scale regions. It is shown that the areal population density of fish groups can be estimated from their incoherently averaged, broadband matched filtered scattered intensities. A numerical Monte-Carlo model is developed to determine the statistical moments of the scattered returns. It uses the parabolic equation to simulate acoustic field propagation in random range-dependent ocean waveguides. The effects of (1) multiple scattering, (2) attenuation due to scattering, and (3) modal dispersion on fish population density imaging are examined. Results of the model are applied to interpret OAWRS images of shoaling Atlantic herring populations acquired during the 2006 Gulf of Maine experiment. Multiple scattering and attenuation are found to be negligible at OAWRS frequencies employed in the experiment and for the herring densities observed. Coherent multiple scattering effects, such as resonance shifts, are significant for small highly dense fish groups on the order of the wavelength, but negligible for larger groups. Optimal sound speed for charting scattered returns in range within the random waveguide is found to roughly equal the group speed of mode 1.
Three-dimensional passive localization of cavitation activity for quality assessment of clinical high-intensity focused ultrasound devices.
Authors: Faragher Stuart , Gyöngy Miklós , Collin Jamie , Hodnett Mark , Hurrell Andrew , Coussios Constantin-C.
Published: October 2010

The widespread adoption of high-intensity focused ultrasound (HIFU) as a modality for non-invasive treatment of malignant tissue will rely heavily on the implementation of robust and reliable quality assessment (QA) procedures. Previous work has demonstrated the viability of using cavitation emissions as a QA tool for rapid mapping of the acoustic fields generated by HIFU transducers. The present work details the design, implementation, and experimental validation of a cylindrical array surrounding the HIFU focus for 3-D passive mapping of cavitating fields produced by clinical HIFU transducers. The configuration of array elements was first optimized for accurate mapping of cavitation activity both on-axis and off-axis by modeling the received signal from a collection of broadband sources. A novel 50-element array was subsequently manufactured from PVDF using a novel printed circuit board technique. Testing of the array has been conducted by mapping the extent and evolution of the cavitation field produced by various HIFU intensities in a tissue-mimicking material, and the results have been compared to the extent of the region over which cavitation would be expected from hydrophone-based characterizations of the HIFU field.
Modeling nonlinear acoustic waves in media with inhomogeneities in the coefficient of nonlinearity.
Authors: Demi L. , Verweij M. D. , van Dongen K. W. A.
Published: October 2010

The refraction and scattering of nonlinear acoustic waves play an important role in the realistic application of medical ultrasound. One cause of these effects is the tissue dependence of the nonlinear medium behavior. A method that is able to model those effects is essential for the design of transducers for novel ultrasound modalities. Starting from the Westervelt equation, nonlinear pressure wave fields can be modeled via a contrast source formulation, as has been done with the INCS method. An extension of this method will be presented that can handle inhomogeneities in the coefficient of nonlinearity. The contrast source formulation results in an integral equation, which is solved iteratively using a Neumann scheme. The convergence of this scheme has been investigated for relevant media (e.g., blood, brain, and liver). Further, as an example, the method has been applied to compute the 1-D nonlinear acoustic wave field in an inhomogeneous medium insonified by a 1 MHz Gaussian pulse propagating up to 100 mm. The results show that the method is able to predict the propagation and the scattering effects of nonlinear acoustic waves in media with inhomogeneities in the coefficient of nonlinearity. This motivates a similar extension of the 3-D INCS method.
Traditional brass instruments of the world.
Authors: Wheeler Paul A.
Published: October 2010

The brass family of musical instruments are lip-reed aerophones. In the western musical tradition, they are usually made of brass or other metals; however, in non-western musical traditions they may be made of shell, wood, bone, bark, bamboo, animal horn, or metal. In spite of the material used for construction, all lip-reed aerophones are commonly referred to as brass instruments. This paper introduces various brass instruments used in traditional music around the world. These include the erke of Bolivia, the alphorn of Switzerland, the amankondere of Uganda, the shofar of Israel, the sringa of India, the dung-chen of Tibet, the nabal of Korea, the didjeridu of Australia, and the conch of Oceania. The paper includes the cultural setting and sound clips of the various instruments.
Musical consequences of nonlinear sound propagation in brass instruments.
Authors: Logie Shona , Campbell Murray , Chick John , Myers Arnold , Gilbert Joel
Published: October 2010

More than 20 years ago the pioneering work of Beauchamp showed that nonlinear sound propagation in brass instruments resulted in musically significant modification of the timbre of the radiated sound. Since then it has been demonstrated that nonlinear propagation is responsible for the “brassy” timbre which characterizes the sound of trumpets, trombones, and horns played at very high dynamic levels. It has also been recognized that different subgroups of the brass family can be distinguished by the rate at which nonlinear distortion develops during a crescendo. In this paper measurements are presented of the transfer function between mouthpiece and bell for brass instruments with different minimum pipe diameters and bore profiles, over a range of dynamic levels typical of those used in playing. These measurements are compared with the results of simulations of wave propagation based on weakly nonlinear 1-D propagation theory in an attempt to clarify the musically significant consequences of nonlinear propagation.
The natural frequencies of muted circular drums.
Authors: Young Frederick J.
Published: October 2010

The natural frequencies of circular drum heads are calculated by the use of finite elements. The results for unmuted drum heads are almost identical to the well known analytical solution expressed in Bessel functions. Mutes of various sizes and shapes are used to stop a section of the head from vibrating. For example, a circular damper having one-quarter of the drum head diameter raises the resonant frequencies of the first eight modes of vibration by 11%, 1.7%, 15.1%, 3.8%, 6.2%, 9.2%, 5.2%, and 10.1%. For the undamped drum head, modes two and three are identical. Modes four and five are identical as well as modes seven and eight. Each of the pairs have differing resonant frequencies. The changes in resonant frequencies are strongly influenced by where the mute is placed. It would seem that the calculated frequency changes could be used to musical advantage.
Modeling bar-resonator interaction in mallet instruments.
Authors: Neby Lindsey R. , Blodgett Earl D.
Published: October 2010

Mallet instruments, such as the marimba, rely on appropriately tuned resonators placed beneath the bar to enhance their sound. If the resonator is tuned to match the frequency of the bar, the loudness is enhanced in exchange for a reduced sustain time [I. Bork, Appl. Acoust. 46, 103–127 (1995)]. A simple model for the bar-resonator interaction is presented, treating them as a coupled system of damped oscillators. [Work supported by the U.S. Department of Education Ronald E. McNair Post-Baccalaureate Achievement Program.]
Evaluating violin quality: How consistent are skilled players?
Authors: Saitis Charalampos , Scavone Gary P. , Fritz Claudia , Giordano Bruno L.
Published: October 2010

A perceptual experiment was designed to investigate how consistent violinists are at evaluating violin quality. The objective was to examine both intra- and inter-subject consistency across a certain range of violins. Skilled classical violinists were asked to play a set of different violins, evaluate their quality, and order them by preference. Violins of different periods were used, varying from student to performance level. Low light conditions and dark sunglasses were used to hide the identity of the instruments as much as possible. Considering the bow as an extension of the player, violinists carried out the task using their own bow. Upon completing the task, participants had to comment on the ranking process and provide rationale for their choices. Preliminary results from a pilot study indicate that both intra- and inter-subject consistency are high when violinists are presented a small group of instruments that are fairly distinct from one another. Results of a more in-depth study (with more instruments, some very similar to one another) will be presented at the conference.
Wind turbine aeroacoustic noise and noise mitigation strategies.
Authors: Asheim Michael , Papas Paul , Moriarty Patrick , Collis Jon
Published: October 2010

Wind turbines are becoming an important piece of the solution to low-carbon power production. However, as more turbines are installed near population centers, the environmental impacts associated with these machines, such as noise, are also becoming more obvious. Aeroacoustic noise is generally thought to be the greatest source of acoustical noise in wind turbine systems. This study will present measurement results collected at the National Wind Technology Center on an operating wind turbine that characterize the total received acoustic field surrounding the turbine. Designs and preliminary measurements of trailing edge modifications to the outboard airfoil sections will be discussed as a means of partial noise mitigation. In addition, future aeroacoustic noise treatments and measurement plans will be mentioned.
Broadband active noise control with transfer path equalization.
Authors: Pabst Oliver , Sachau Delf
Published: October 2010

Active systems for noise reduction are typically of interest for applications in which low-frequency noise is a main source of disturbance and only limited amounts of installation space and payload are available. When applying active noise control methods in small aircraft cabin area such as the crew rest compartment of a long range jet, the transfer path between sensor and actuator is strongly influenced by room acoustics and transducer behavior, thereby affecting control in a frequency selective manner, especially when using filtered reference algorithms. In this study, a concept for transfer path equalization in a feedback-control approach with virtual microphones and the feedback filtered-reference least mean squares algorithm are evaluated. The implementation and influence of the prediction-error filter based equalizer on broadband active noise control are analyzed in simulation as well as in experiments in an acoustic mock-up. The use of the equalizer improves broadband attenuation (f < 350 Hz) by 3–4 dB with a total attenuation of 20 dB at the error sensor.
Talkers compensate for feedback shifts within their vowel regions.
Authors: Katseff Shira , Houde John F. , Johnson Keith
Published: October 2010

The speech motor control system adjusts articulatory plans when there is a discrepancy between observed and expected feedback. Expected auditory feedback has been proposed to come from one of two sources: (1) an internal estimate of the speaker’s current articulatory state, as generated by passing the current set of motor commands through an internal model [K. Wolpert and B. Shadmehr (1999)], or (2) an acoustic region associated with the intended phoneme or syllable accessed from memory. This experiment tested whether vowel expectations are phoneme-specific or state-specific by examining responses to shifts in auditory feedback within a subject’s vowel region. A state-based feedback expectation predicts that talkers will detect and compensate for shifts within their vowel regions, while a phoneme-region-based feedback expectation predicts no ability to detect and compensate for such within-region shifts. Subjects in this experiment produced /Cud/ words “bood”, “food”, and “rude”. F2 feedback was shifted slowly up by 300 Hz or down by −300 Hz: the shifted vowel sounded either like the fronted /u/ in California English “dude” or like the back /u/ in California English “who’d”. Subjects compensated for these within-region feedback shifts as well or better than they did for out-of-region feedback shifts, consistent with a state-based feedback expectation rather than a phoneme-based expectation.
On the relation between overlap and release.
Authors: Ipek Canan
Published: October 2010

This study is about the relation between gestural overlap and acoustic release. The aim is to define a set of different temporal relations from which the presence/absence of release in between two consecutive gestures can be predicted. The overlap of two consecutive gestures is here defined as the co-occurrence in time of their articulatory closure intervals. In this study, however, what is measured is the acoustic closure duration of stop consonants. In this context, an acoustic index of overlap—closure duration ratio—and release percent in every binary combination of the voiceless stop consonants—p, t, k— have been measured at word and sentence boundary and at two different vowel contexts, /a/ and /e/. Stop release does not have a phonologically contrastive function, yet languages systematically differ from one another in whether stops are released or not at specific contexts. Resulting from this fact, the argument in this study is that release is a result of specific temporal relations between two consecutive gestures, and these relations are part of the phonological representation.
A test for errors of phonological rule processing.
Authors: Gormley Andrea , Logan John
Published: October 2010

As a cognitive process, phonological alternations should be subject to error under high cognitive load. An experiment was designed to determine if phonological processes err by comparing two sets of tokens; one that contained a rule and a second set, matched in form, that did not. Samples were obtained from 16 speakers for two types of stimuli: one targeting the phonological process of flapping and the other targeting the phonological process of schwa-insertion. Acoustic analyses were performed to determine the normal range for each speaker. Tokens that fell two standard deviations outside of this range were counted as errors. The frequency of errors was compared to see if the phonological rule condition had more errors. The forms with flapping and schwa-insertion did not induce more errors than the comparison forms without these processes. The results do not provide sufficient evidence for the existence of rule processing errors. This result calls into question the status of these phonological alternations as cognitive processes.
Gestural reorganization in Mandarin contracted syllables.
Authors: Li David C.
Published: October 2010

“Syllable contraction” is a type of spontaneous pronunciation in Chinese that reduces a sequence of syllables to a lesser number [Cheng (1985)]. The present study examines the phenomenon under the framework of articulatory phonology, in which speech is composed of gestures whose timing is controlled by a system of planning oscillators [Goldstein et al. (2006)]. The experiment tests the hypothesis that Mandarin contracted syllables result from a transition from anti-phase to the more stable in-phase coordination between vowel gestures of successive syllables. Such phase shifts have been implicated in sound changes in other languages [e.g., Parrell (2009)]. If such shifts occur, vowels in contracted words should exhibit coproduction of (lexically) sequential vowels. This is tested by comparing disyllabic function words, which are more likely to be contracted [Tseng (2001)], to non-function words. Results show that F2 is lower when the vowel in contracted disyllabic words is followed by a front vowel lexically and higher when the vowel in contracted words is followed by a front vowel lexically. The absence of such effects where the vowels do not differ in backness confirms that the effect is a result of coproduction. These results thus support the gestural organization hypothesis for Mandarin contraction.
Voicing assimilation and prosodic structure in Spanish.
Authors: Campos-Astorkiza Rebeka
Published: October 2010

Voicing assimilation of syllable final /s/ is a widely reported feature of the Spanish sound system ([razgo] “feature” versus [rasko] “I scratch”). However, there is a lack of non-impressionistic data supporting claims in the literature regarding its behavior. This study presents an acoustic analysis of this assimilation process and discusses its main phonetic correlates in relation to the production of voicing. Furthermore, voicing assimilation offers an ideal situation to test the interaction between a segmental process and prosodic structure. Previous research has shown that gestures are larger in prosodically strong positions, including stressed syllables [Beckman and Edwards (1994); Pierrehumbert and Talkin (1992)]. Thus, we would expect more assimilation when stress falls on the syllable following /s/ than when it falls on the syllable containing it (/rás.go/ versus /ras.gó/), under the assumption that greater gestural magnitude results in more overlap among adjacent gestures and, consequently, leads to more assimilation. This paper presents an experiment that tests the degree of voicing assimilation in Castilian Spanish under different segmental and prosodic conditions. Preliminary results suggest that assimilation is variable and does not always result in complete voicing of /s/. These findings are modeled as the result of changes in gestural magnitude and overlap.