bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of acoustical transmission and reflection from a sandy stratified rough sediment using the grain shearing model
Authors: Guillon Laurent , Aleshin Vladislav
Published: May 2008

A number of applications, such as geoacoustic inversion or object detection, require an appropriate theoretical consideration of the sound reflection and transmission problem. The analysis we present here includes three essential aspects: account for a constitutive behavior of a saturated unconsolidated granular material, presence of vertical gradients in material properties, and roughness of the sediment surface. Accepting the Buckingham grain shearing model (see e.g. JASA, vol. 117, pp. 137-152) for the stress-strain relationship in the sediment, the gravity-induced variations of the longitudinal and shear rigidity can be described. The corresponding numerical solution for the plane interface is presented and the influence of infinite rigidity gradients at the surface is discussed. Another important contribution is provided by the interface roughness that considerably improves the penetration conditions. This problem is solved using a statistical treatment of a number of roughness realizations with a given spatial spectrum. The developed numerical tool enables to study the influence of all these factors and estimate the penetrated energy for different acoustical frequencies, roughness parameters, and grain sizes (This work was founded by DGA and Thales Underwater Systems).
Biot-Stoll with squirt flow and shear (BICSQS) model: high-frequency correction
Authors: Chotiros Nicholas P.
Published: May 2008

The modeling of the grain to grain shear stiffness within the larger Biot-Stoll plus contact squirt flow and shear (BICSQS) model [N. P. Chotiros and M. J. Isakson, J. Acoust. Soc. Am. 116(4), 2011-2022, 2004] assumes Poiseuille flow, which must become invalid at high-frequencies. Specifically, the viscous shear drag term will be unphysically large. A correction is introduced based on Biot's solution for oscillatory flow between two parallel plane boundaries [M. A. Biot, J. Acoust. Soc. Am. 28, 179-191, 1956]. Although the original solution was derived for oscillatory fluid flow relative to stationary parallel plane boundaries, it can be readily adapted for oscillatory motion of the boundaries in opposite directions relative to the fluid, as in shear drag at the grain to grain contact. This correction extends the frequency range of the BICSQS model. Theoretical results, with and without the correction, will be compared. Work supported by the Office of Naval Research, Ocean Acoustics.
Sound absorption with fibre-free sintered aluminium in combination with thermally activated concrete slabs
Authors: Rottiers Wouter
Published: May 2008

Due to increasing ecological awareness and growing requirements of human well-being in working environments, contemporary interior design requires sustainable solutions. Consequently, cooling ceilings are an efficient alternative to conventional air conditioning systems with high energy demands. In order to maintain its thermal efficiency however, the ceiling surface must remain uncovered as much as possible. Conventional perforated or grooved acoustical materials allow for sound absorption only in combination with mineral wool or foam, thus presenting a thermal isolating barrier: they obviously decrease the performance of a thermal ceiling. Porous panels made of pure sintered aluminium offer a conductivity up to 96 kcl / mhC with a thermal radiation of 18.4 W / m2K, combined with a broadband sound absorption up to αw = 0.7 without the use of any additional thermally isolating material. The panels meet the environmental, hygienic and fire safety requirements: they are fibre-free, non-combustible (Euroclass A1), rust-, moisture- and chlorine-proof and can be recycled. The unvisible porosity does not give away the outstanding acoustical qualities. Available in several designs and any colour, the sheets are optically identical to a plain, matt aluminium panel. Several possible configurations are discussed.
Couchet Harpsichord soundboard vibroacoustics behaviour: An application of the Impact Nearfield Acoustical Holography (IPNAH)
Authors: Le Moyne Sylvie , Le Conte Sandie , Ollivier François
Published: May 2008

The Music Museum in Paris recently acquired a harpsichord made by Ioannes Couchet in 1652 in Anvers. As a masterpiece this instrument is considered as a "National Treasure" and therefore protected. A challenging problematic has risen when its restoration was decided since the aim was to play this instrument again in concert. In the objectives of increasing our understanding of the harpsichord ageing, improve a numerical model currently in process and develop a diagnostic method for conservation, an experimental modal analysis of the soundboard was performed by processing its sound field. A non intrusive method, the Impact Planar Nearfield Acoustic Holography, was used. This technique, developed by the authors, implements the well known inverse method NAH on the basis of the acoustic impulse response field and is well adapted to modal analysis. NAH is performed here in unusual conditions compared to literature, as they are far from the ideal: unbaffled source, low sound pressure level, unusually large measurement distance, preponderance of evanescent waves. An additional challenge was to muffle strings, as they should not be removed nor slackened. However, a very satisfying modal decomposition for [30-1500Hz] bandwidth is obtained. Results are confronted with literature and an energetic analysis is proposed.
Aspects of vibrato and micromodulation in double reed instrument sounds
Authors: Oehler Michael , Reuter Christoph
Published: May 2008

The perceived naturalness of real and synthesized oboe and bassoon vibrato sounds has been investigated in several perception experiments. The stimuli were generated by means of a currently developed synthesis and analysis framework for wind instrument sounds (first presented at 152nd ASA meeting), based on the pulse forming theory. The framework allows the control of amplitude and frequency parameters at different sound production levels. The stimuli were rated by 60 subjects from "natural" to "unnatural". A conducted ANOVA showed (p<.01) that the different types of modulation significantly affect the perceived naturalness of vibrato sounds: The synthesized stimuli with combined pulse width and cycle duration modulation (source modulation) are perceived as natural as the real sounds. The subsequently modulated synthesized stimuli (AM and/or FM near the end of the signal path) are perceived significantly less natural (p<.01). The results support the hypothesis, that source-affected timbre modulation is an important factor for the perceived naturalness of oboe and bassoon vibrato sounds. The use of the developed framework for wind instrument sounds is an alternative method to analyze (micro-)modulation effects. Further investigations may be useful for exploring new sound synthesis algorithms as well as for other experiments in the field of timbre research.
A case study on the validation of models that predict the impact of aircraft noise on sleep
Authors: McGuire Sarah , Davies Patricia
Published: May 2008

The impact of aircraft noise on sleep disturbance is not accurately assessed by cumulative noise metrics that are often used to predict community impact, such as Ldn, because sleep disturbance is highly dependent on the noise level of individual events. Most existing sleep disturbance models are dose-response relationships that relate the noise level of individual events, as measured by SEL(A) or LAmax to the percent awakened, and independence of responses to individual events is assumed. There are a few models that also incorporate additional parameters such as time of night and noise sensitivity, and some that predict the impact of noise on sleep structure. In order to determine whether a model should be used as a general aircraft noise sleep disturbance prediction tool, its performance in a variety of situations must be evaluated. Data was collected from a number of sleep disturbance studies and comparisons were made between responses and model predictions of awakenings and sleep stages. The sufficiency of the collected data for estimating the parameters of more complex models of sleep disturbance is also discussed.
Comparison of various procedures for the assessment of prominent discrete tones using a large number of sound samples
Authors: Schmidt Lothar , Sagemuehl Dirk
Published: May 2008

The procedures from the standards ISO 1996-2 and DIN 45681 as well as the two procedures (TNR and PR) from ISO 7779 are compared. In the first section, characteristic features of the procedures (e.g. signal analysis parameters, degree of automation and characteristics of the prominent discrete tone analysis) are compared. In the second section, the procedures are applied to approximately 70 sound samples. Besides natural sounds (e.g. from machines), synthetic sounds (e.g. peak in a trough) are also used. The results are compared against assessments of the sounds by human subjects. The results of the comparisons are discussed, with special attention paid to cases where significant deviations occur. The third section looks at the results of the comparisons under the aspect of requirements for a standard (e.g. robustness, precision). Overall it was determined that none of the procedures investigated provides optimal results for all sound samples.
Evidence for vortex transport by surface acoustic waves in a high-Tc superconductor
Authors: Hucho Carsten , Rakel Munise , Wirsig Arno , Jachmann Fabian
Published: May 2008

The interaction of surface acoustic waves (SAW) with the magnetic vortex system in YBa2Cu3O7 is investigated. A 100nm YBCO film is deposited on a piezoelectric substrate and structured for electrical 4-point measurements. Interdigital transducers are fabricated on the same substrate. When applying an external magnetic field perpendicular to the film surface a SAW-induced dc-voltage perpendicular to the acoustic sound-path is observed. This is interpreted as consequence of directed dragging of vortices by the SAW induced dynamic pinning structure [1]. The piezoacoustic wave acts as a conveyor for mobile flux quanta. Additional ac-dc-conversion as result of the nonlinear current-voltage characteristics close to the superconducting transition temperature can be resolved and separated. In order to observe the sound-induced vortex motion directly, the flux distribution is analyzed magnetooptically. Magnetooptic imaging allows for time resolved analysis of flux distribution. Quantitative analysis of changes in the magnetization distribution when acoustic driving fields are applied is carried out. The influence of piezoacoustic waves on the pinning properties and sound-induced depinning is discussed. [1] F. Jachmann and C. Hucho, Sol. State Comm., 142 (4) (2007), 212
A comparison between interaural level difference and interaural correlation uncertainty on binaural signal detection thresholds
Authors: Le Goff Nicolas , Kohlrausch Armin , Breebaart Jeroen
Published: May 2008

Experiments were performed to study the effect of the presence of interaural level differences (ILDs) on binaural detection abilities. The subjects had to detect an interaurally out-of-phase 500-Hz tone in the presence of a diotic noise masker that had a bandwidth of either 1 kHz, 100 Hz or 10 Hz. Experiments were conducted for both frozen and running-noise conditions and ILDs up to 30 dB were applied to both signal and masker. The results indicate an ILD dependency that varies with the bandwidth of the masker. Furthermore, with increasing ILDs, the difference in detection thresholds between frozen and running-noise conditions was larger for narrow-band noise conditions. Similar observations were made by previous investigations on the influence of reduced masker correlation. Both data sets are compared in order to find possible similarities in the mechanisms involved in the detection tasks.
Effects on cochlear frequency selectivity after hypobaric pressure exposure
Authors: Brännström Jonas , Grenner Jan
Published: May 2008

The effects of hypobaric pressure chamber exposure was measured in noise in ten patients with monaural fluctuating low-frequency hearing loss (FLFHL) such as Ménière's disease using psychophysical tuning curves (PTC), transiently evoked otoacoustic emissions (TEOAE), binaural pitch matches and speech recognition scores (SRS) in noise. In the literature, reversible hearing losses have been observed in about 50 % of the patients, but sometimes improved SRS can be observed in patients without hearing threshold improvement. This indicates possible effects of pressure treatment on cochlear frequency selectivity. The relative overpressure in the middle ear obtained after repeated exposures in hypobaric pressure chamber (total duration 18.5 to 28 minutes) was used to impose pressure gradients to the inner ear. The results indicated that the treatment effects were small, but slightly improved SRS in noise, TEOAEs emission strength and PTCs were observed after treatment. Pure tone hearing thresholds improved only for patients exposed to longer treatment durations. Subjective improvement at follow-up could not be predicted from the results. Although the effects were small, the data suggest that hypobaric pressure treatment may improve cochlear frequency selectivity in the affected ear in patients with monaural FLFHL.
Perceptual explanations of articulatory variability in the realisation of the nasal feature for the consonants
Authors: Vaissière Jacqueline
Published: May 2008

This paper illustrates how the perceptual constraints explain the observed articulatory and aerodynamic inter-speakers and inter-languages variability between initial nasal consonants (/n/), and unreleased final consonants (/N/). In the case of /n/, only a short, well-defined region around the consonant release needs to be nasalized for the consonant to be perceived as nasal. In the case of /N/, because of the lack of a nasal release, a longer span is needed for deciphering the presence of nasalisation; contextual nasalization of the preceding vowel can be avoided, but in that case, the nasal murmur has to be long to be perceived (since the first part of the murmur is perceptually masked by the vowel), and/or /N/ has to be released. Such observations argue for the division of the nasal consonant into three parts, onset, murmur and release: the realisation of the nasal feature is aligned around the /N/ onset, and around the /n/ offset. It also argues for a better integration of the perceptual requirements and masking phenomena in modelling the observed variability. Finally, it shows that a feature can be realized very differently depending on the position of the phoneme in the syllable.
Double focus in general American English
Authors: Liu Fang
Published: May 2008

This study investigates the acoustic realization of double focus in statements and declarative questions in English. Five speakers produced eight sets of utterances with alternating focus (medial, final, or double) and sentence type (statement or declarative question) conditions. F0 analyses indicate that the effect of double focus on the global pitch range and the local pitch target is somewhat moderate when compared to that of single focus: 1) Post-focus pitch range suppression shows a smaller magnitude in double- than in medial-focused statements, 2) Post-focus pitch range raising is less dramatic in double- than in medial-focused questions, and it ends before the stressed syllable of the second focus in double-focused questions, in order to realize a rising pitch target for the on-focus stressed syllable, and 3) pitch targets of on-focus stressed syllables are more fully realized (i.e., showing steeper slopes or higher registers) in single- than in double-focused sentences. Duration analyses indicate that the length of the double-focused item is in between those of the corresponding single- and non-focused item, with the single-focused stressed syllable having the longest duration. These findings demonstrate a delicate balance among the realization of lexical stress, focus, and sentence type in English.
Model-based algorithms for detecting damage in ultrasonic nondestructive evaluation measurements
Authors: Clark Grace A.
Published: May 2008

This work addresses the "As-Built" modeling problem in ultrasonic nondestructive evaluation (NDE), in which one is given measurements of a mechanical part before and after use. The condition of the "as-built" part (prior to use) is known, so that after the part has been used, it can be tested for damage. This enables a two-step model-based approach: (1) Given input-output measurements (A-Scans), estimate a dynamic prediction-error model of the "as-built" measurement(s) using system identification algorithms. The model is validated by testing the innovations (residuals) for statistical whiteness and then stored for future use. (2) Later, when testing the part for damage, the error between the measurement and the output of the stored model is tested against a short-term whiteness confidence interval test statistic. If the part passes the test, this implies that the model remains valid and the part is declared undamaged. If the part fails the test, this indicates a model mismatch, which means that the part's acoustic properties have changed, and the part is declared damaged. Performance of the algorithms is demonstrated using real measurements, receiver operating characteristic (ROC) curves and a confidence interval about the probability of correct classification.
Underwater channel characterization using opportunity sources : a time-frequency-phase approach
Authors: Ioana Cornel , Jarrot Arnaud , Gervaise Cédric , Quinquis Andre , Mars Jérôme I.
Published: May 2008

Analyzing natural signals constitutes the main tool for characterization of physical phenomena. Underwater channel is an example of a natural environment potentially characterized by signals generated by various sources : underwater mammals, human activity noise, etc. In order to efficiently exploit the information from these signals two major problems should be addressed. First, since the signals are unknown or disturbed by unpredictable factors, we are deal with a blind processing context. That is, the lack of a priori hypothesis has to be considered. Generally, the signal has a complex shape characterized by multi-component non-linear time-frequency structures. The proposed solution consists in focusing our processing on non-parametric time-frequency analysis considering also fundamental signal items such as time-frequency energy and local phase analysis. The second problem is related to the complex connection between physical parameters of a phenomenon and parameters of signals characterizing this phenomenon. The proposed approach consists of combining the physical model with the information provided by a parametric representation of the signal. This framework helps to the definition of the concept of underwater passive tomography which provides the characterization of the underwater channel of interest by taking advantage of environmental signals : mammals vocalizations, motion sources, etc.
Horizontal structure of acoustic intensity fluctuations in the ocean
Authors: Uscinski Barry J. , Nicholson Jim
Published: May 2008

In April 1989 an acoustic experiment was performed over the abyssal plain south of Msderia in which transmissions were made, for about an hour, at 482, 680 and 740Hz from a ship steaming at 5kts to a receiving array towed by another ship 65km away travelling on a parallel course at the same speed. The signals arrived by two paths, an upper path trapped in the surface duct and a lower path via the main sound channel. This paper describes the experiment and analyses the intensity fluctuations in the signal received by the lower path. We investigate the horizontal structure of intensity fluctuations in the ocean when these are mainly due to internal waves. This aspect of such acoustic intensity fluctuations has received little attention until now. The experimental results are compared with theoretical predictions based on the parabolic moment equations for propagation and scattering in randomly irregular media, and on the stnadard Garrett-Munk model for ocean internal waves. The experimental results and theoretical predictions agree quite well but some new questions arise about the correlation of intensity fluctuations as the acoustis transmission frequency is varied.
Numerical design of Alberich anechoic coatings with superellipsoidal cavities of mixed sizes
Authors: Ivansson Sven M.
Published: May 2008

Thin rubber coatings with cavities in a doubly periodic lattice are able to reduce reflections of underwater sound by redistributing normally incident energy such that absorption in the surrounding rubber is enhanced. For spherical scatterers, the anechoic effect can be studied numerically by the layer multiple-scattering method. In comparison to more flexible but also more computer intensitive methods, such as FEM modeling, there are two important advantages. An improved physical understanding of the anechoic effect can be achieved by simplified semianalytical analysis, and the high computational speed allows modern global optimization techniques to be applied for coating design. In this paper, the flexibility of the layer multi-scattering method is improved by combination with an efficient algorithm for numerical computation of transition matrices for superellipsoidal scatterers. Extensions to mixtures of nonspherical scatterers of different types are also considered, in order to enhance the broad-band performance. Symmetry properties are used to reduce the size of the pertinent equation systems. Examples of numerical coating design for underwater acoustic applications are presented, using differential evolution algorithms for the optimization.
The influence of absorption on statistical distribution of free path lengths in rooms
Authors: Sumarac Pavlovic Dragana , Mijic Miomir
Published: May 2008

The ray tracing method in sound field simulation in a room allows the calculation of the free path lengths distribution (FPL) by superimposing all rays paths generated in the analysis. In room acoustics the statistical theory of sound field defined this distribution as an indicator of room geometrical properties which are independent of absorption. Accordingly, some commercial softwares for ray tracing simulation allow user to calculate that global distribution of FPL only. This paper is concerned with the analysis of the changes in the shape of FPL distribution as a consequence of nonuniform arrangement of absorption in room. Particularly is analysed the impact of absorptive auditorium in different global forms of the halls where all other interior surfaces are acoustically hard.
Measuring the mixing time in auditoria
Authors: Defrance Guillaume , Polack Jean-Dominique
Published: May 2008

The goal of prediction, in Room Acoustics, is to synthesize the impulse responses (IRs) of a hall, in order to derive acoustic indices or to allow auralization. The process assumes the hall to be a time invariant linear system. Furthermore, the IR is known to behave stochastically when the sound field becomes diffuse, that is, after a certain time called mixing time. This study aims at characterizing the IR mixing time. Three methods are presented for visualizing and detecting the time evolution of the IR behaviour. The first one highlights the transition from early reflections to diffuse sound field by monitoring the phase evolution versus time. The two others exploit the gaussian distribution of pressure in a diffuse sound field, when the IR becomes statistical. These methods are applied to measurements, carried out in Salle Pleyel, and confirm the simple relationship found earlier between mixing time and volume.
Prediction method for the acoustic performance of permanent form systems
Authors: Chene Jean-Baptiste , Guigou-Carter Catherine
Published: May 2008

Permanent form systems considered in this paper combine a layer of porous or fibrous material onto which a concrete layer is poured. Such systems allow the fulfillment of French thermal regulations. However, their acoustic performance is quite limited. Indeed, the acoustic performance of the concrete layer is usually reduced by the presence of the porous or fibrous layer. The modeling of such multi-layered structures submitted to acoustic excitation is discussed in this work. The behavior of such a system is investigated by using a wave approach based prediction tool. The porous layer is modeled following Biot's theory. The effect of the metallic anchors that connect the fiber and the concrete layers is also investigated. The acoustic performance of such systems is studied both experimentally and analytically. A parametric study is performed to identify the most determinant parameters. The model is thus used to obtain insight into the behavior of such systems in order to develop solutions that result in improved acoustic performance.
A comparison of impulse-like sources to be used in reverberation time measurements
Authors: Horvat Marko , Jambrosic Kristian , Domitrovic Hrvoje
Published: May 2008

As a part of an extensive ongoing research on reverberation time measurements, efforts have been made to find an impulse-like source that will comply with certain demands concerning its spectral content and sound pressure levels it can provide. Although the relevant standards state that such kind of sources should be avoided due to the lack of measurement repeatability, their use has proved to be necessary due to inability of conventional omni-directional loudspeakers to provide adequate sound pressure levels, especially at the low end of the frequency range of interest, thereby ensuring sufficient dynamic range. Therefore, the emphasis of this investigation has been made on peak sound pressure levels and the amount of low frequency content each source is able to provide. The investigated sources include 6 mm and 8 mm pistols, firecrackers with different amount of explosive compound and explosive mixtures of acetylene gas.
Measuring Sound Insulation using Deconvolution Techniques
Authors: Hak Constant C. , Van Hout Nicole H. , Martin Heiko J.
Published: May 2008

To compare the acoustic performance of a building element with the given sound insulation requirements, measurements need to be done. Generally, a broadband noise source is used according to international standards. This method does not always work in practice due to high sound insulation values or high background noise levels. It is very inconvenient from a practical point of view or even impossible to perform an accurate sound insulation measurement for all frequency bands. A solution to this problem can be found in deconvolution techniques using mls or sweep signals. It is possible to increase the signal to noise ratio with these techniques by averaging measurements and spreading out the spectral sound energy in time. As a result an efficient use of available sound power is possible. In a laboratory is investigated how to use mls or sweep signals as a source signal and deconvolution as a measurement technique to obtain the sound insulation under noisy conditions.
Characterising a washing machine as a structure borne sound source on a lightweight floor
Authors: Lievens Matthias
Published: May 2008

The transfer of structure borne sound power depends on the mobility of the source and the receiver. If source and receiver are coupled through multiple points, the interaction between those points has to be accounted for. The force of a washing machine injected into a lightweight wooden floor is analysed to develop a simple measurement procedure for similar multiple point structure borne sound sources. A complete mobility model will be compared with a simplified model based on a reduced mobility matrix. The importance of different matrix components will be determined. Receiver structures used in real buildings will be investigated.
Influence of the source orientation on the measurement of acoustic parameters in a large reverberant cathedral
Authors: Arana Miguel , San Martin Ricardo , San Martin Maria Luisa
Published: May 2008

ISO 3382 standard describes both definitions and measurement procedures of different acoustic parameters derived from the room impulse response. Regarding to sound sources, most of the commercial dodecahedron loudspeakers comply with the maximum allowed directional deviations of the source specified in the standard. However, the influence of its specific orientation may affect the results obtained on some parameters more than their subjective just noticeable difference-jnd- at least in rooms with no high reverberation times. An interesting aim is to study such influence in function of the liveliness of the room. A detailed measurement set is been carrying out in a reverberant place (Cathedral of Tudela, Spain) with the objective to analyze the influence of the source's orientation-apart from its acoustic characterization. In addition to dodecahedron loudspeakers, pseudo-impulsive sources are been used in order to compare results from a statistical point of view. Results obtained will be compared with those obtained in several concert and theater rooms.
Uncertainty analysis in acoustical modeling of room
Authors: Mleczko Dominik
Published: May 2008

For a long time there is a need in industry of acoustical modeling of rooms. It is necessary for new production room design, machine exchange, renovation or enlargement of production rooms, change in a production profile or acoustical room adaptation for acoustical work conditions improvement. In such cases modeling quality is essential and thanks to uncertainty analysis it is possible to quantitatively estimate the effect that input parameters value variation has on model behavior. The article presents general rules for sound pressure level prediction uncertainty calculation in a room. By partial uncertainty calculation analysis of input parameters influence on uncertainty prediction an effort was taken to find parameters with biggest influence on the prediction process. As an example an industrial production room is presented which was modeled to predict noise level on a work stands after it was expanded.
Electrophysiological and behavioral measures of temporary threshold shift in a bottlenose dolphin (Tursiops truncatus)
Authors: Finneran James J. , Schlundt Carolyn E. , Branstetter Brian K. , Dear Randall L.
Published: May 2008

Auditory evoked potentials are being increasingly applied to more advanced studies of marine mammal hearing, such as frequency selectivity, temporal processing, and temporary threshold shift (TTS). In this study, both behavioral and electrophysiological techniques were used to measure TTS in a bottlenose dolphin exposed to 20-kHz tones. Behavioral hearing thresholds were estimated using a modified staircase procedure and a whistle response. Electrophysiological thresholds were assessed using the multiple auditory steady-state response. Evoked potential stimuli consisted of seven frequency-modulated tones having carrier frequencies from 10-70 kHz and unique modulation rates. Tones were simultaneously presented and the evoked response at each modulation rate independently tracked to test hearing at all seven frequencies simultaneously. The behavioral and evoked response data both showed frequency-dependent patterns of TTS, with the largest shifts at 30 kHz; however, TTS measured using evoked potentials (up to 40-45 dB) was always larger than that observed behaviorally (19-33 dB). This discrepancy may be the result of the evoked response input-output function, which can be represented as the sum of two processes, a low threshold, saturating process and a higher threshold linear process, that react and recover to fatigue at different rates.
Directional sensitivity and hearing pathways in the beluga whale, Delphinapterus leucas
Authors: Pacini Aude , Nachtigall Paul E. , Mooney T. Aran , Castellote Manuel , Taylor Kristen A. , Esteban José-Antonio
Published: May 2008

Although much variation exists in jaw morphology among species, odontocetes are believed to receive sound primarily through the pan bone region of the lower jaw. In order to further examine this jaw hearing hypothesis, we tested the head receiving sensitivity and directional hearing of a beluga whale, Delphinapterus leucas. Hearing measurements were conducted with a 9-yr-old female beluga using the auditory evoked potential technique. A preliminary audiogram indicated that the subject had very sensitive hearing (45-55dB from 32-80 kHz) and heard up to 128 kHz. The pathway investigation used a piezo-electric transducer to present the click stimuli, whereas the hearing directivity was measured in the far field, also using broadband clicks. Like the bottlenose dolphin, the subject had a region of high sensitivity around the pan bone region (78 dB), however, unlike the bottlenose dolphin, we found that the region of maximum sensitivity was at the tip of the lower jaw (75dB). The subject also proved to have highly directional hearing. This study supports the shaded receiver hypothesis and also shows that hearing pathway variations appear to exist among odontocete species and are at least partially dependent on head morphology.
Interactions of frequency components of multi-component envelope following response in a beluga
Authors: Supin Alexander Y. , Popov Vladimir V.
Published: May 2008

The envelope-following response (EFR) in odontocetes is composed of overlapping ABRs produced by each cycle of rhythmic sound stimulus at a rate of a few hundred cycles per sec. It has been shown recently (Finneran et al., JASA 2007, 121: 1775) that a complex stimulus consisting of a few carriers modulated by different rates produces a complex EFR composed of components reproducing all the modulation rates. Using this technique, interactions between different components of complex EFR were investigated in a beluga whale Delphinapterus leucas. When all carriers of the complex stimulus were equalized by SPL, the interaction depended on both the SL of carriers (their level relative the threshold) and inter-carrier frequency spacing. Addition of components of higher SL (at low-threshold frequencies) dramatically reduced the amplitudes of other EFR components, especially at short frequency spacing. The leading factor of this reduction was decreasing of the modulation depth of each of the carriers when the overall power of the stimulus increased by additional components. The threshold estimate of each carrier little depended on the number of components; however precision of threshold determination fell down with increasing the number of stimulus components due to the reduced amplitudes of EFR components.
Validation of adjoint-generated environmental gradients for the acoustic monitoring of a shallow water area
Authors: Meyer Matthias , Hermand Jean-Pierre , Berrada Mohamed , Asch Mark
Published: May 2008

In the framework of the recent Maritime Rapid Environmental Assessment sea trial MREA07/BP'07 [Le Gac&Hermand, 2007] that was conducted in the same area south of the island of Elba as the earlier Yellow Shark trial (YS94), this paper examines the original YS94 acoustic data and the recent MREA07 oceanographic data to demonstrate adjoint-based acoustic monitoring of environmental parameters in Mediterranean shallow waters. First, adjoint-generated environmental gradients are validated for the application in geoacoustic inversion where the bottom acoustic parameters of the YS94 layered seabed are determined from the long-range waterborne propagation of a multi-frequency signal. Then, for the application in ocean acoustic tomography, the temporal variability of the MREA07/BP'07 oceanographic data is analyzed in terms of empirical orthogonal functions and the adjoint-based inversion scheme is used to track the time-varying sound speed profile of the experimental transect.
Geoacoustic Adjoint-Based Inversion via the Parabolic Equation
Authors: Papadakis John S. , Hermand Jean-Pierre , Flouri Evangelia T. , Meyer Matthias
Published: May 2008

In this paper an analytic method is exhibited for recovering the acoustic parameters of the sub-bottom region in the ocean. The acoustic propagation problem is modeled via the wide angle parabolic equation and the bottom boundary condition used is in the form of a Neumann to Dirichlet or Dirichlet to Neumann map. The sub-bottom region is assumed homogeneous or horizontally stratified with homogeneous layers. The inversion is modeled as an optimal control problem, and the solution is based on the adjoint method. Several cost functions are introduced which make use of the relative amplitude of the observed complex field. The method is applied to several test cases and satisfactory convergence of the inversion scheme is exhibited.
Experimental confirmation of negative dispersion and Bayesian inversion of multimode propagation in a bone-mimicking phantom
Authors: Bauer Adam Q. , Anderson Christian C. , Marutyan Karen R. , Bretthorst G Larry , Wear Keith A. , Holland Mark R. , Miller James G.
Published: May 2008

Previously we demonstrated using numerical simulations that negative dispersion observed in bone can result from the interference of two propagating modes, each of which exhibits positive dispersion, consistent with the Kramers-Kronig predictions. [J. Acoust. Soc. Am. 120, EL55-61 (2006)] One goal of the present study was to demonstrate this negative dispersion experimentally using the simplest example of a bone-mimicking phantom that is capable of producing two such interfering modes. An additional goal was to establish that, with the experimental data serving as input to a Bayesian approach to the inverse problem [J. Acoust. Soc. Am. 121, EL8-15 (2007)], reliable estimates of the underlying properties of the bone-mimicking phantom could be obtained from the measured signals. The phantom consisted of a flat and parallel PlexiglasTM plate into which a step discontinuity was milled. The phase velocity and attenuation coefficient (3 to 7 MHz) of the phantom were measured with a 0.25-inch piezoelectric receiver and calculated using both broadband and narrowband data. Negative dispersion was observed at specific spatial locations near the step where the attenuation coefficient rose approximately linearly with frequency. Results demonstrate that interference between modes can result in negative dispersion and that Bayesian inversion can yield underlying material properties.
The role of bone marrow on acoustic properties of cancellous bone - finite difference time domain modelling study
Authors: Kallioniemi Antti S. , Töyräs Juha , Hakulinen Mikko , Jurvelin Jukka
Published: May 2008

Quantitative ultrasound (US) parameters are related to structure and properties of cancellous bone. The effect of bone marrow on US propagation, i.e. absorption and scattering, is still poorly understood. However, substitution of fatty marrow with water is known to significantly affect the US parameters. The present study investigates the role of marrow on US parameters, using microtomography based 3D-finite difference time domain (FDTD) modelling. Eleven human cancellous bone samples were analysed with a micro-CT system (SkyScan 1072) to determine microstructure and morphology. Wave 3000 Pro software (Cyberlogic Inc.) was used for simulations. Models were created to simulate experimental US measurement geometry with focused 1MHz transducers. Simulations were repeated before and after replacing the marrow with water. The voxel size of the simulation mesh significantly affected sample structure and simulations. US attenuation and speed decreased and increased, respectively, when marrow was replaced with water (p<0.01). US reflection at sample surface and backscattering from internal structures increased (p<0.01) when marrow was replaced with water. Contribution of bone marrow was stronger in samples with low bone volume fraction. This implicates that inter-individual differences in the composition of marrow may significantly affect measured ultrasound parameters, especially when investigating osteoporotic bone with low density.
A virtual headphone based on wave field synthesis
Authors: Laumann Klaus , Theile Günther , Fastl Hugo
Published: May 2008

The term "virtual headphone" refers to specially designed loudspeaker systems aiming for transmission characteristics equal to real headphones. Particularly of interest is the exact pre-filtering of the speaker signals to compensate the effect of head related transfer functions (HRTFs) between loudspeakers and ear canal. These so-called "HRTF inverse filters" are dependent on geometrical conditions and so they have to be updated with every head movement. In order to avoid problematic adaptive HRTF inverse filtering, the real loudspeakers are replaced by focussed sources generated according to the principles of Wave Field Synthesis (WFS). Head tracking controlled adjustment of driving functions allows easy source movement and thus fixed source positions in relation to the listener's ears, providing stable virtual headphone reproduction. A single static HRTF inverse filter network can be used. It is designed to ensure precise headphone equalization according to ITU-R BS.708 and offers accurate reproduction of e.g. binaural signals. A pilot study with a circular WFS array built in a panel above the listener's head has verified the functional capability of this concept.
Sound generation by airflow in a pipe having a small internal cavity
Authors: Kristiansen Ulf , Nygård Bo/rge
Published: May 2008

Gas flow through corrugated pipes is known to excite strong acoustic resonances within the pipe. In an attempt to better understand the flow acoustic phenomena involved, we have investigated experimentally a short pipe (0.6m long and 0.04m diameter) having a single small (5mm long, 2.5mm deep) circumferential cavity. It was found that if placed close to the pipe's inflow end, strong acoustic resonances were generated. The experimental results were compared to a model based on describing-function theory. The model involves two transfer functions, one associated with the pipe resonator, and the other the shear layer above the cavity. These are combined to a feedback system. This model gives the frequencies generated and the acoustic pressure levels (to within a constant) for different flow velocities. Reasonable agreement was obtained between the experimental results and the model predictions.
Notes on the reproduction of moving virtual sound sources
Authors: Ahrens Jens , Spors Sascha
Published: May 2008

Wave field synthesis and higher-order Ambisonics are two representatives of sound reproduction systems that are based upon the concept of physical recreation of a desired sound field. Conventional implementations of such systems typically reproduce moving virtual sound sources as a concatenation of static source positions that change over time. This approach introduces various artifacts which are reported in the literature to be strongly audible. It was recently shown by the authors that the explicit consideration of the physical properties of the sound field of moving sources in the reproduction algorithm avoids these artifacts. It thus allows for the accurate reproduction of the Doppler Effect. In practical implementations of such sound field reproduction systems unavoidable artifacts arise. These are mainly a consequence of sampling and truncation of the loudspeaker distribution and appear both for static and moving virtual sound sources. For static sources, they are well documented in the literature. We revisit these investigations and point out the particularities of these artifacts with respect to the time-variant property of the reproduced sound field.
Acoustics in the public school classroom
Authors: Hansen Uwe J , Darvennes Corinne
Published: May 2008

As mentioned in a DAGA 07 paper 1, physical science preparation in American schools often leaves something to be desired. In recent years the ASA Committee on Education in Acoustics has made an effort to participate in finding relief for that problem. Three approaches have been of some influence. 1. Teacher workshops; 2. Hands-on student sessions. 3. Secondary school curriculum input. Teacher workshops have emphasized music as a vehicle to introduce science in the elementary classroom. Hands-on student sessions have included about 20 acoustics experiments of varying degrees of sophistication for students both in high school physics classes and in elementary general science classes. Secondary curriculum input has included both, development of laboratory experiments in acoustics, and exposure to relatively low cost educational versions of computational software. Examples of teacher workshop content, a number of hands-on experiments, and some finite element calculations will be discussed. 1Musik: Zugang zur Wissenschaft in der Grundschule. Uwe J. Hansen, DAGA 2007, Stutgart pp. 171-172.
Acoustics Modules Developed in the IIT Research Experience for Teachers Program
Authors: Muehleisen Ralph T.
Published: May 2008

From 2004-2008, the Illinois Institute of Technology (IIT) received funding from the US National Science Foundation (NSF) to institute a program to bring K-12 (primary and secondary school) teachers into University research labs for a seven week summer program where teachers work with an IIT faculty Research Mentor and develop an educational module for their students based on their mentor's research. The module's goal is to introduce students to engineering design concepts, utilizing scientific inquiry techniques, and incorporating an ethics component and a design project. Additionally, the modules must be linked to the Illinois State Board of Education Learning Standards. In 2005, a teacher developed a module for teaching high school algebra, geometry, and physics using musical acoustics, culminating with a woodwind instrument design project. In 2006, a teacher developed a module for a 3rd grade science class that explores the basics of sound and hearing, culminating in a noise control design project. This paper will present and discuss these two acoustic teaching modules. This project was supported by NSF grant EEC-0502174.
Ur[ban]sonate: Echoes of twentieth-century sound art in the urban elementary classroom
Authors: Summers Kevin N. , Summers Jason E.
Published: May 2008

The sonic arts provide a variety of cross-disciplinary entry points into the traditional lower-elementary curriculum. The exploration of sound poetry provides students with a workspace to deconstruct the connection between written and spoken language; phonemes; phonics; voiced, unvoiced, stressed and unstressed letter sounds and blends. Kurt Schwitters's "Ursonate," the music and scores of John Cage, various other sound art works and Deep Listening (TM) techniques provide a bridge to the study of acoustic sound and serve to validate/contextualize students' desires to creatively explore physical phonemes such as the relationship of pitch to frequency of vibration. After creating symbolic representations of sounds, writing sound poems and creating musical instruments, students synthesize learned material by scoring and directing the performance of original sound art pieces.
Vibrating-String Coupling Estimation from Recorded Tones
Authors: Lee Nelson , Smith Julius O.
Published: May 2008

Coupling of vibrational polarizations in a single string, for an instrument such as the acoustic guitar, produces psychoacoustically significant effects such as beating and two-stage decay (Weinreich, JASA v62 n6). Previous considerations of string coupling phenomena appear not to have addressed the practical problem of calibrating computational models based on recorded tones. In this work, we take a data-driven approach using measured data from a vibrating string from an acoustic guitar, the motion of the string in two orthogonal planes, and formulate a regularized least-squares problem for computing the coupling between the measurements. Such a formulation ensures that the resulting coupling is physically admissible, in that the resulting coupling factors do not generate energy, and are easily found as the problem is convex. Well-studied algorithms for solving convex problems, such as interior-point and gradient descent methods can be used and are widely available in the form of open-source libraries.