bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustical dissipation due to phonon-phonon interaction, thermoelastic loss and dislocation damping in MnO and CoO
Authors: Singh Rishi Pal , Singh Manish Pratap , Singh Rajendra Kumar
Published: May 2008

The temperature dependent acoustical dissipation due to phonon-phonon (p-p) interaction, thermo-elastic mechanism and dislocation damping due to screw and edge dislocations have been evaluated in MnO and CoO in fcc (NaCl-B1 type) phase, in a wide temperature range 50 ⩽ T ⩽ 500K for longitudinal and shear modes of propagation along three crystallographic directions viz. <100>, <110> and <111>. Electrostatic and Born repulsive potentials were used to obtain second order and third order elastic constants (SOEC and TOEC), taking interactions up to next nearest neighbours.The SOEC and TOEC obtained at diffrent temperatures have been used to obtain gruneisen parameters and non-linearity or anisotropic parameters which in turn were used to evaluate (α/f2) for longitudinal and shear waves. Specific heat (as function of Debye temperature), hardness parameter, lattice parameter have been used as input data. It has been found that (α/f2) increases with temperature and the acoustical dissipation is mainly influenced by p-p interaction.The possible implications of results have been discussed.
Numerical and experimental results on sonic band gaps in 1-D phononic crystals with a symmetric stub
Authors: De Billy Michel , Hladky-Hennion Anne-Christine , Vasseur Jérôme , Djafari-Rouhani Bahram
Published: May 2008

The wave propagation in periodic systems has received a great deal of attention during the last years. By analogy with the studies driven on photonic crystals, many works were conducted on phononic crystals. In this paper the propagation of elastic waves through a one dimensional chain of beads with grafted stubs is experimentally as well as numerically investigated. The results obtained by both approaches are well correlated and show that the stub introduces a dip in the spectral response of the chain. The numerical analysis shows that this dip is due to the excitation of a stub mode that cancels the transmission from one extremity of the chain to the other. The position and the shape of the dip in the response are related to the geometry and nature of the stub. The results show that it is possible to adjust the position of the dip and open potential applications of these structures for filtering or demultiplexing. Finally first results on periodically grafted stubs in the chain are presented.
Atomization and deviation of cylindrical water jets in a transverse acoustic field
Authors: Carpentier Jean-Baptiste , Baillot Françoise , Blaisot Jean-Bernard , Dumouchel Christophe
Published: May 2008

This work deals with a particular breakup mode experienced by cylindrical liquid jets when submitted to an intense transverse acoustic wave. Experiments on low speed water jets (< 1 m/s) of diameters 3 mm and 6 mm show that sound waves with a frequency ranging from 500 Hz to 1800 Hz can produce bulges along the jet. When the sound level is high enough, these bulges can trigger an effective atomization mechanism where the jet flattens as a liquid sheet before disintegrating. Sound field can also induce steady deviation of the jet. Both phenomena are theoretically studied. A first model, which treats bulges as outward marks of one particular mode of vibration of the liquid column, is proposed. This model leads to a criterion for the onset of atomization that satisfactorily agrees with experimental observations of the present work. A second analysis identifies deviations as radiation pressure effects. It predicts the direction of experimental deviations with success.
Numerical and experimental observations of azimutal shock waves
Authors: Marchiano Régis , Thomas Jean-Louis , Brunet Thomas , Coulouvrat François
Published: May 2008

Acoustical Vortices (AV) are acoustical beams with a phase singularity of screw type. They possess a phase with an helical structure which is winding around the axis of propagation. These twists of phase engender special properties such as the existence of an associated angular momentum and imply a coupling between the axial and transverse components of the beam. Propagation of AV of finite amplitude follows the classic rule of nonlinear acoustics. Beyond a shock formation distance, AV develop shocks, but the structure of the latters is noticeable. It will be shown by numerical simulations and experimental measurements, that the nonlinear propagation of AV gives birth to 3D shock waves: a classical shock in the direction of propagation plus an azimutal one in the transverse plane. The numerical simulation, based on an original algorithm solving the 3D Khokhlov-Zabolotskaya equation, is used to investigate the dynamic of the formation of the azimutal shock. Experimental observations made with ultrasonics in water confirm the existence of particular shock waves. Finally, a brief discussion of the potential applications will be proposed.
Water flow generation owing to interaction between pulsing bubble and rigid wall
Authors: Drozhzhin Alexey P. , Teslenko Vyacheslav S.
Published: May 2008

Generating a directed water flow in periodic forming a non-symmetrical acoustic field was experimentally investigated in the work. Periodic acoustic wave field was formed with the help of a vapor-gas bubble pulsing in the hole of a thin diaphragm near a rigid wall. Alternate formation of two water flows moving in opposite directions was found. During the bubble growth stage the flow at velocity V1 was formed in the opposite direction of the plate, and during the bubble collapse stage the flow at velocity V2 was formed towards the plate. By changing the parameter k=R/r where R was a distance from the hole center to the rigid wall, and r was a hole radius, the possibility to control average values V1 and V2 was shown. It was found that at k=R/r=5.8 V1=V2, at k>5.8 V1>V2, and at k<5.8 V1 was less than V2. It was shown that due to variation of the distance between a pulsing bubble and a rigid wall it was possible to control velocity V and direction of the total flow of water through the hole. The maximum value of velocity V reached 40 cm/s in the experiment.
A pair of spectral notches which plays a role as a spectral cue in the vertical localization, and it's application to estimation of sound source elevation from binaural signals
Authors: Iida Kazuhiro
Published: May 2008

The author [Applied Acoustics, 68, 835-850 (2007)] proposed a parametric HRTF model for vertical sound localization. The parametric HRTF is recomposed only of the spectral peaks and notches extracted from the measured HRTF. The results of the median plane localization tests, which were carried out using the parametric HRTFs with various combinations of spectral peaks and notches, show that the pair of first and second notches (N1 and N2) above 5 kHz can be regarded as spectral cues. In this research, estimation of the elevation of sound source in the upper median plane by extracting N1 and N2 frequencies from binaural input signal was carried out. The kinds of sound sources were female voice, male voice, music, white noise, and pink noise. The results show that the estimation is accurate for almost of all the elevation and of all the kind of sound sources.
Trading of intensity and interaural correlation cues in the perception of loudness
Authors: Culling John F. , Lewis Hannah G.
Published: May 2008

When a signal is added to noise in the NoSπ binaural configuration, a reduction in interaural cross-correlation (IACC) occurs at the signal frequency. Increases in tone intensity produce decreases in IACC. Consistent with this relationship, direct manipulations of IACC can result in the perception of an added signal and progressive reduction in IACC produces progressive increases in the loudness of this signal [Culling et al. 2001 J. Acoust. Soc. Am. 110, 1020-1029]. In the present study, a narrow sub-band of noise (460-540 Hz) embedded within a broadband (0-3 kHz) diotic noise was manipulated in both intensity and IACC in a 3-interval, odd-one-out task. In the reference intervals, IACC was zero and the spectrum was flat. In the target interval, both the IACC and the intensity of the target band were incremented. These increases have opposing effects on loudness. Correct identification of the target interval followed a U-shape as a function of the size of intensity increment. The minimum of the function was at chance performance, indicating that the opposing cues were fully traded.
IPods listening levels on London Underground
Authors: Dance Stephen , Wash Phil
Published: May 2008

In the last 5 years the prevalence of the iPod/MP3 players has grown exponentially. The use of such in-earphones under urban conditions has been reported widely in the press at the anecdotal level. This study compared listening levels under quiet conditions and that representative of a London Underground train journey. Calibrated recordings of underground trains running in tunnels were played through loudspeakers in an anechoic chamber, whilst pop music or speech podcasts were played through the iBuds. Thirty-three participates listened to the iPod whilst a Binaural Head and Torso measured the noise levels through the in-earphones. The participants had time to adjust the volume setting on each occasion. A small audiometric study was undertaken for those participates with particularly high and low volume settings a week after the tests were completed. Results show very high volume settings were used when speech was played with the train noise.
The Healthy Benefits of Isolating Earphones
Authors: Voix Jeremie , Le Cocq Cecile , Hager Lee D.
Published: May 2008

With the ubiquitous presence of Personal Stereo Players (PSPs), namely iPods™ and the like, many hearing conservationists have raised concerns about the temporary and permanent hearing damages that could result from long exposure to loud music playback, especially among adolescents and teenagers. The crux of the problem can be identified as an overexposure of the auditory system. In order to reduce the dose received by the PSP listener, the playback level and/or the duration should be reduced. Assuming that the duration of the music playback experience is really up to the user, the remaining parameter is the music playback level. The purpose of this study is to first understand - from the available public and scientific literature - what factors are influencing the PSP playback level; and second, to investigate if the use of earphones featuring good attenuation of the ambient noise level would lead to a reduced playback level, hence a reduced dose and eventually less auditory damage. Other benefits on sound quality that are associated with isolating earphones will be presented in a third part. Finally the article will review other safety mechanisms that could be used in earphones and PSP to make them safe for the hearing.
Auditory and somatosensory goals for sibilants
Authors: Perkell Joseph S. , Matthies Melanie L. , Ghosh Satrajit S. , Maas Edwin , Hanson Alexandra , Guenther Frank H. , Lane Harlan , Ménard Lucie , Tiede Mark
Published: May 2008

In prior studies [JSLHR 47, 1259-69, 2004; JASA 116, 2338-44, 2004], we found that speakers' auditory acuity for synthetic sibilant (/s/, /sh/) and vowel stimuli was correlated with the degree of acoustic contrast they produced. This outcome is consistent with the view that the articulatory movements underlying phonemic contrasts have auditory goals. There was also a cross-speaker relation between sibilant contrast and use of contact between the tongue tip and lower alveolar ridge for /s/ (but not /sh), indicating that such contact is a somatosensory goal for /s/. In the current study, another, larger group of subjects also showed relations between measures of auditory acuity and acoustic contrast for sibilants and vowels. To determine whether the idea of a somatosensory goal for /s/ would also be supported by a relation between acuity and contrast, we made measurements of somatosensory discrimination. Small plastic (JVP) domes with grooves of different spacing were pressed against each subject's tongue tip and the subject was asked to identify one of four possible orientations of the grooves. A wide range of individual performance was observed with a bias-corrected sensitivity measure. Correlations with produced sibilant contrast and further analyses will be reported. [Research supported by NIDCD, NIH.]
Production and perception of vietnamese short vowels
Authors: Viet Son Nguyen , Carré René , Castelli Eric
Published: May 2008

It is well known that vowels can be produced in isolation, acoustically stable in such a way that they are represented as points in the F1-F2-F3 space. Vietnamese language presents 13 vowels, however, Vietnamese can only pronounce 9 vowels [i, u, e, o, ω, a, σ, ε, γ] in isolated mode. A previous study showed that the 4 remaining vowels [α, δ , ν , ε ] have the same acoustic characteristics (F1, F2, F3) as, respectively, the vowels [a, ε, σ, γ], but their dynamic characteristics (the rate of CV transitions) are clearly distinct. Measurements show us that vowels durations of [α, ν] are always shorter than the one of corresponding classical vowels [a, γ] and are not acoustically stable. For test perceptions (with 10 Vietnamese people), synthesized syllables [a-t] and [γ-t] with changing vowel duration are recognized as [α-t, ν-t] when then duration of initial vowel [a, γ] are 60% - 70% shorter. It means that the vowel duration is an important parameter that allows Vietnamese distinguishing the long vowels and short vowels in Vietnamese language. This paper further analyses the production of Vietnamese CV, including long vowels and short vowels in terms of duration, formant evolution and rate of C.V transitions.
Audiovisual perception of prosodic contrastive focus in whispered French
Authors: Dohen Marion , Loevenbruck Hélène
Published: May 2008

This study investigates the potential contribution of visual information in the audiovisual perception of prosodic contrastive focus in French. Contrastive focus is used to attract the listener's attention to a specific part of the utterance. Mostly conceived of as auditory/acoustic, it also has visible correlates which have been shown to be perceived. This study aimed at analyzing the interaction between audition and vision for the perception of prosodic focus by using a whispered speech paradigm. It was based on audiovisual recordings from 4 speakers wearing no facial markers. It combined performance assessment to reaction time measurements and confirmed and extended preliminary results obtained on 2 speakers wearing facial markers (needed for a parallel articulatory analysis). The results showed that adding vision to audition for the perception of prosodic focus can not only improve perception performances but can also reduce perceptual cognitive load. A further analysis suggested that the two modalities are integrated for the perception of prosodic focus. Visual only perception was facilitated for whispered speech suggesting an enhancement of visual cues. Moreover, the absence of facial markers did not impair perception. Therefore facial markers do not seem to enhance the relative importance/salience of visual cues.
Melodic prominences structures: exploring to what extent the speaker variability is spreading
Authors: Caelen-Haumont Geneviève
Published: May 2008

Melodic prominences in speech have a deserved reputation of conveying a great part of variability, as they are greatly based on subjective impulse and feelings. We think that these specific contours are nevertheless relevant, and that their structure, while obeying to internal laws of regulation, allow also a range of speaker variability. Generally no specific tool was used to describe these FO contours with precision. An automatic analysis tool MELISM was then developed by Caelen-Haumont and Auran (2004) allowing accurate descriptions of F0 salience (melisms). This paper aims at 1° describing the MELISM tool, the automatic segmentation, the annotation, the melodic labelling of the melism structure it provides in the prosody domain 2° presenting the main results over 4 speaker exploring to what extent the speaker variability spreads. The melism structures are explored and analysed such as the whole variability is reduced through three major components (onset, nucleus, coda) and their respective subparts, where only the nucleus is the compulsory part. Statistics running on these structures put to light a set of interesting laws about the internal regulation of melisms but in the other side, the part devoted to the speaker variability.
Imaging the earth's subsurface via regularized inversion
Authors: Clapp Robert
Published: May 2008

Modern seismic exploration geophysics attempts to construct a model of the earth's subsurface using measurements taken at the earth's surface. The recorded measurements comprise datasets with billions to trillions of samples. Despite the size of the datasets, models are often poorly sampled because of the complexity of the earth's subsurface. Therefore, the resultant model is poorly determined for many components. The massive size of our problems introduce additional limitations. We are limited to adjoint-based inversion methods, we can never afford to iterate to true convergence, and most importantly we make approximations to the physics in our operators. These limitations introduce spurious events when inverting. Significantly improved results can be obtained by incorporating regularization that incorporates a priori knowledge of the physics and geology into the inversion process.
Evolution of the statistics of the unscattered component of low order acoustic modes as a function of range
Authors: Chandrayadula Tarun K. , Wage Kathleen E.
Published: May 2008

Scattering due to internal waves in the ocean causes the acoustic modes to exchange energy as they propagate. At a specific range, the mode signal consists of two components: the unscattered component is the energy that has propagated only in the designated mode and the scattered component contains the contributions from other modes. The unscattered component dominates the signal at short ranges, but decays to zero at longer ranges. If the unscattered component can be isolated from the scattered energy, it could be used in tomographic inversions. Signal processing techniques are needed to detect the unscattered component. A statistical model for the unscattered component that would help design signal processing techniques is currently unavailable. This talk describes a new model for the unscattered component that was developed using coupled mode and parabolic equation simulations. The model characterizes the statistics of the unscattered component using parameters such as frequency and time coherence. The characteristics of the unscattered component are then compared with the scattered component. The implications of these results for the design of detectors is briefly discussed. [Work supported by ONR Ocean Acoustics Graduate Traineeship Award]
Exact and approximate moments for dispersive pulse propagation
Authors: Cohen Leon , Loughlin Patrick
Published: May 2008

We derive exact moments for pulse propagation in a dispersive medium. These moments are not only inherently interesting but clarify the validity of a recently proposed approximation scheme for wave propagation. The approximation method for pulse propagation is based on the Wigner position-wave/number representation and is very accurate, easy to apply, and moreover is physically illuminating. In particular one obtains the evolved approximate Wigner distribution from the initial Wigner distribution by a simple linear translation in phase space. Propagation with damping is also taken into account. We will show that the reason for the high accuracy of the approximation is that the important low order moments are exactly given by the approximation and that these low order moments preserve very well the basic shape of the pulse. Moreover, now that we understand why the approximation method works well, the approximation can be systematically improved. We give a number of specific examples of exactly calculable moments to illustrate the method and we compare exact and approximate moments. The work of PL is supported by The Research of LC was supported by AFOSR and the work of PL is supported by ONR (N00014-06-1-0009)
Effect of array element location on coherent inter-array processing
Authors: Debever Claire , Kuperman William A.
Published: May 2008

In the SWellEx-96 experiment, two 25-elements horizontal arrays, each of length 250 m, were moored 3.5 km apart [N.O. Booth et al, IEEE, JOE, 25, no 3, July 2000]. A broadband source (50 to 400 Hz tones) was towed from 1 km to 10 km away from the arrays. The data is processed using the simple conventional plane-wave beamformer for all the cases covering incoherent frequency and incoherent inter-array processing to coherent frequency and coherent inter-array processing as a function of source position relative to the arrays. The effect of noise and array element location mismatch on source localization and coherent processing gain is investigated. An attempt to improve array element localization is made using a self-focusing technique. [Work supported by ONR.]
Longitudinal Correlation Improvement with Model-based Technique
Authors: Zhang Renhe , Li Fenghua
Published: May 2008

Longitudinal correlation coefficient is one of the most important parameters for signal processing in ocean acoustics. Multi-path interference is an important effect on the decrease of the longitudinal correlation for low frequency sound propagation in shallow water. In this research, the Frequency-Phase-Shift Relationship (FPSR) between the Frequency Response Function (FRF) of sound propagation at two horizontally separated locations based on waveguide invariant is derived. The validity of the FPSR is demonstrated by both numerical simulations and data from two experiments. Experimental data also show that the decrease of the longitudinal correlation coefficient of low frequency signals from explosive source due to multi-path interference can be conquered significantly with the FPSR. [Work supported by the National Natural Science Foundation of China under Grand No 10734100].
Direct wave suppression using wavelet transform for bistatic sonar
Authors: Lei Bo , Ma Yuanliang , Yang Kunde , Sun Chao
Published: May 2008

The bistatic sonar is often influenced by the direct wave, especially when the target approaches the baseline of the system. The direct wave is above 50dB higher than the scattering signal level. The paper analyzes the effect of the direct wave, and proposes a new method based on wavelet transform for direct wave suppression. The strong direct wave is well eliminated while maintaining the weak scattering signal almost unchanged. The basic idea is that the direct wave is firstly removed form the received signal after wavelet transform. Then the signal is reconstructed in time domain, finally the cross-correlation is achieved to shown the doppler frequency shift of the weak scattering signal. Computer simulation is given. The cross-correlations of the received signal for both before and after the direct wave suppression are compared. It shows that the influence of the direct wave is correctly removed, the time delay and Doppler frequency shift are shown in the figure and the target is detectable.
Adaptive beamforming applied to underwater acoustic measurements
Authors: Orlov Denis , Fiks Iosif , Fiks Galina , Korotin Pavel , Turchin Victor
Published: May 2008

In many applications, such as measuring the underwater noise level of moving ships, underwater acoustic measurements face serious difficulties related to several factors, including low signal-to-noise ratio, effects of surface and bottom on signal, as well as complicated spatial structure of the sea interference. The increase of the measurement interference resistance, compared to the case of a single receiver (hydrophone), can be provided by the use of spatially distributed receiving systems (antenna arrays), which are able to suppress the interference due to their spatial selectivity. The present work is aimed at developing adaptive methods for underwater acoustic measurements with the use of vertical antenna arrays. The method must provide the maximum reduction of external interference keeping the given measurement accuracy, i.e., the result must coincide with the output of a single receiver in the absence of interference. From the point of view of synthesis of array systems, the originality of the presented approach is mainly in conjunction of measurement functionality of the antenna array and the maximum interference suppression. The results of numerical simulation and experimental testing under sea conditions show that the proposed adaptive methods provide high precision of measurements under strong and/or complex interference conditions.
Modeling of underwater sonar barriers
Authors: Elminowicz Andrzej , Zajaczkowski Leonard
Published: May 2008

Commonly used Diver Detection Sonar (DDS) are characterized by detection and tracking as well as intruder warning in limited range 300 m ÷ 600 m. A new approach to underwater protection is focused on multi-monostatic, bistatic and multistatic active sonar barriers (ASB). This paper describes key features of a multi-monostatic (MM), bistatic (BS) and multistatic (MS) operation in the littoral beginning from system configuration, its performance and constraints. A new type of acoustic devices in a form of a transmitting/receiving module and its application in active sonar barriers (ASB) has also been presented. Coverages and ranges of barriers for various technical parameters, environmental conditions and wave propagation as well as modules location (including transducers' depth, azimuth and inclination) have been studied. The application of active sonar barriers (ASB), especially in protection systems, has been presented as barriers protecting docks, harbour basins, ships at piers or harbour entries. The new type of a monostatic/bistatic acoustic barrier in technology demonstrator form, has been designed and constructed. In order to display detection and localization of the small underwater objects as well as their tracking and classification the performance tests of the barrier will be conducted. The results of the tests will be attached to the paper.
Wideband sonar system for autonomous surveys using REMUS
Authors: Capus Chris , Pailhas Yan , Brown Keith E.
Published: May 2008

Many new roles are being proposed for Autonomous Underwater Vehicles (AUVs) to carry out hazardous tasks in harsh or remote locations and to free up valuable resources required for manned missions. These roles include marine environmental survey, target detection and classification and tracking of underwater pipes and cables. Suitable sensing and processing packages must be provided and building on recent wideband sonar research, the Ocean Systems Laboratory (OSL) is putting together a wideband system for deployment on board a REMUS AUV. The prototype sensor package comprises paired projectors and receivers mounted in a side-looking arrangement to provide complementary information to the standard REMUS sidescan modules. The sensor bandwidths cover a range from 30-130kHz similar to those used by the bottlenose dolphin. Data is gathered autonomously with a dedicated AMD Geode based PC104+ PC controlling a 4-channel 800kHz simultaneous sampling data acquisition module. Acquisition is triggered to coincide with mission requirements from a separate mission control PC on board the vehicle.
Optoacoustics: Can ultrasound become the preferred modality for molecular imaging
Authors: O'Donnell Matthew
Published: May 2008

Optoacoustics can be used to image the distribution of optical absorption in tissue, combining the specificity and sensitivity of optical imaging with the high resolution and penetration of ultrasound imaging. It represents one of the most promising techniques for molecular imaging because the optical absorption of bioconjugated nanoparticles can greatly exceed that of tissue over a range of wavelengths in which light can penetrate multiple centimeters into the body. We have explored several types of nanoparticles conjugated to a range of antibodies targeted to several important biological systems. Here we discuss two potential applications of bioconjugated gold nanorods, one for cancer cell targeting and the other to identify inflamed endothelial cells signaling the early stages of atherosclerosis. Optoacoustic images of cell cultures and animal models demonstrate the sensitivity and specificity of these nanosystems for molecular imaging. To translate these experimental findings into a clinically acceptable molecular imaging modality, we have also explored integrated optical systems able to deliver the optical pulse for optoacoustic excitation and detect the resultant ultrasonic waves using an all-optical transducer. The basic operating principles of this device, and the prospects for ultrasound-based molecular imaging using it, will be discussed.
Acoustical Society of America Distinguished Service Citation
Authors: Crum Lawrence A. , Hartmann William M. , Kuhl Patricia K.
Published: May 2008

The Distinguished Service Citation is awarded to a present or former member of the Society in recognition of outstanding service to the Society.
Acoustical Society of America R. Bruce Lindsay Award
Authors: Holland Christy K. , Roy Ronald A. , Crum Lawrence A.
Published: May 2008

The R. Bruce Lindsay Award (formerly the Biennial Award) is presented in the Spring to a member of the Society who is under 35 years of age on 1 January of the year of the Award and who, during a period of two or more years immediately preceding the award, has been active in the affairs of the Society and has contributed substantially, through published papers, to the advancement of theoretical or applied acoustics, or both. The award was presented biennially until 1986. It is now an annual award.
Irregular sound absorbers work better
Authors: Sapoval Bernard , Rozanova-Pierrat Anna , Félix Simon , Filoche Marcel
Published: May 2008

The diffraction and absorption of waves by a system with both absorbing properties and irregular geometry is an open physical problem. In the same time, irregular absorbers have been shown to be extremely efficient (1). A more reachable and closely related goal is the understanding of wave oscillations in confined systems containing an absorbing material with an irregular shape. From the theoretical point of view, the difficulty lies in the fact that part of the propagation occurs in a lossy material for which the wave operator is non-hermitian. It is found here that, in resonators containing an irregular shaped absorbent material, there appears a new type of localization. This phenomemon, that we call ''astride'' localization, describes the fact that these modes exist in both the lossless and the lossy regions. They are then both lossy and well coupled to sources in the air. A numerical computation of the time decay of acoustic energy shows that indeed sound absorbing devices work better when presenting a very irregular shape and that this is directly linked due to the existence of astride localisation. (1) Fractal Wall, product of Colas Inc., French patent N0-203404; U.S. patent 10/508,119.
A brief review on micro-perforated sound absorbers
Authors: Nocke Christian , Hilge Catja , Scherrer Jean-Marc
Published: May 2008

The theory and design of microperforated panel sound-absorbing constructions have been introduced by D.-Y. Maa in 1975. Since then many variations of micro-perforated sound absorbing devices and materials have been introduced. Materials that have been used to be micro-perforated have been metal, wood, plastics and many others. A survey of different applications of micro-perforation will be presented. Examples shown in more detail are the development of stretched foils and metal as micro-perforated panels. Results of sound absorption measurements of various assemblies for normal and statistical incidence of sound will be shown and compared with theoretical predictions. Finally the potential of the micro-perforated sound absorber will be discussed.
Distribution of Speech Intelligibility Metrics in Classrooms with Varied Signal to Noise (S/N) Ratios
Authors: Bayazit Tamer Nurgun
Published: May 2008

In a classroom to provide adequate speech intelligibility is vital especially when young children are concerned. Room acoustical characteristics of classrooms like reverberation times and background noise mainly define the speech intelligibility in classrooms. Excessive background noise deteriorates the signal to noise ratio (S/N) and leads to reduction in learning efficiency. An extensive measurements study is being used in Istanbul Elementary Schools as part of a project. This paper explains the results of the investigation of the influence of varying signal to noise ratios on different speech intelligibility metrics. Background noise are includes external noises such as outdoor traffic noise, noise from playground or noise from adjacent classrooms. STI, RASTI, Alcon(%) values of 20 different classrooms in 20 different schools are measured in 9 different positions. The measurements were repeated in each classroom while windows were open and closed respectively. The object of the work was to systematically study the influence of the S/N ratio variations and reverberation time on the different speech intelligibility metrics. Finally to elucidate the effects of different absorption treatments achieving recommended reverberations on the measured speech metrics are also discussed.
Speaker comfort and increase of voice level in lecture rooms
Authors: Brunskog Jonas , Gade Anders C. , Payà Bellester Gaspar , Reig Calbo Lilian
Published: May 2008

Teachers often suffer health problems or tension related to their voice. These problems may be related to there working environment, including room acoustics of the lecture rooms which forces them to stress their voices. The present paper describes a first effort in finding relationships between the objectively measurable parameters of the rooms and the objective voice power produced by speakers. In rooms with different sizes, reverberation time and other physical attributes, the sound power levels produced by six speakers where measured while giving a short lecture. Relevant room acoustic parameters were also measured in the rooms and subjective impressions from about 20 persons who had experience talking in these rooms were collected as well. Analysis of the data revealed significant differences in the sound power produced by the speaker in the different rooms. It was also found that these changes were mainly related to the size of the room and to the gain or support produced by the room. To describe this quality, a new room acoustic quantity called 'room gain' is proposed.
A new technique for the measurement of the normal incidence absorption coefficient using an impedance tube and a single microphone with fixed position
Authors: Vuye Cedric , Vanlanduit Steve , Van Nieuwenhuyse Karl , Guillaume Patrick
Published: May 2008

The normal incidence absorption coefficient of acoustic materials can be measured inside an impedance tube with different settings for the microphone(s). The two most widespread techniques are the standing wave method using a probe microphone and side-mounted two-microphone techniques. Errors that can occur here are related to phase mismatch between the two microphones and the knowledge of the exact locations of the (acoustic centre of the) microphones and test sample. These problems have (partially) been solved by, for example, calibrating the microphones by swapping them and calculating a calibration transfer function or by using one microphone techniques. In this article we will present a novel technique which will also avoid the need for the knowledge of the exact microphone location by continuously moving the sample under test. Different results will be presented and compared to the traditional techniques.
Measurement uncertainty of the sound absorption coefficient
Authors: Izewska Anna
Published: May 2008

The standard ISO/IEC 17025:2005 on the competence of testing and calibration laboratories requires that these laboratories shall apply procedures for estimating the uncertainty of their measurement results. One of the possibility is to evaluate the budget of uncertainty, taking into account all components that contribute significant uncertainty to the final result. In case of the sound absorption coefficient measurement, carried out according to the standard EN ISO 354:2003, the overall uncertainty is first of all influenced by the reverberation times T1, T2 and the power attenuation coefficients m1 and m2, calculated according to the ISO 9613-1 standard and representing the climatic conditions in the reverberation room. In spite of very little difference between the values m1 and m2 representing the change of climatic conditions (usually, it is the case in laboratory), exponential form of the coefficient's function causes that the uncertainty of measurement results increase with frequency very fast. Particularly for the high frequencies, the values of uncertainty are so important that the evaluation of the sound absorption coefficient is practically not possible.
On the use of scaled models in building acoustics
Authors: Wittstock Volker , Schmelzer Martin , Kling Christoph
Published: May 2008

Experimental studies of physical effects in building acoustics are usually time consuming and expensive. This is mainly caused by the building costs but also by the experimental effort. It is thus desirable to have another method for the investigation of basic effects in building acoustics. Building acoustic problems are characterized by the interaction between airborne and structure-borne sound fields. It is therefore possible to use scaled models when both sound fields are treated correctly. This means that the wavelengths in the airborne and in the structure-borne sound fields have to be scaled in the same way. With a scaling factor of typically 1:8, the costs can be reduced drastically and nearly all model parameters can be changed separately. Due to these advantages, this technique is used at PTB's building acoustics group. This contribution gives an overview on the physical background of scaled models, reports on validation experiments and on several applications e.g. investigations of the influence of temperature and static pressure, damping effects, geometry influence on the sound insulation of walls, the measurement of the flanking transmission of walls and the measurement of suspended ceilings.
Measurement of reverberation time with rotating microphone in test chamber and its problems
Authors: Sato Hiroshi , Yoshimura Junichi , Sugie Satoshi , Koga Takashi , Toyoda Emi , Ryu Jongkwan
Published: May 2008

When measurement of reverberation time is done in a test chamber to evaluate acoustical property of materials, spatial averaging of reverberation time should be done. Using microphone rotator is recognized as one of the tool to do spatial averaging. This study compares between three methods of spatial averaging of reverberation times measured in small rectangular test chamber (3m x 4m x 5m). The first method is averaging reverberation time measured at 5 of fixed position used as standard positions for testing, the second is at 72 fixed positions on the circle of microphone rotator, and the third is with microphone rotator (64 s/rotation). The result of comparison between three method revels that reverberation time measured by rotating microphone has more scatter than and presents different reverberation time from those measured by other method especially at lower frequency bands. Simulation of microphone rotation with the decay curves measured at 72 fixed positions suggests that spatial distribution of steady state sound pressure level, rotation speed of microphone, and reverberation time of test chamber are key factors of errors. As a conclusion, the strict guideline for measurement of reverberation time with microphone rotator should be presented to minimize errors.
Uncertainty in building acoustics
Authors: Scholl Werner , Wittstock Volker
Published: May 2008

In many countries, legal requirements exist with respect to the acoustical performance of buildings and building elements. Therefore information about the uncertainty of measured or predicted building acoustic properties is urgendly needed. The complexity of the problem becomes obvious taking sound recuction index R as an example: R represents the ratio of incoming and transmitted sound power of a building element. For practical reasons, the direct measurement of R is replaced by a spatiotemporally averaged sound pressure level difference in two limited rooms, adjusted by the absorption of the receiving room. In doing so, unwanted influences occur like modal effects, flanking transmission, structural power exchange between laboratory and specimen, deviation from ideal diffuse sound fields with unknown consequences etc. For economic reasons, often only one sample is tested and declared 'typical' for the whole family of products without regarding their spread. As a consequence, the uncertainty most often is felt to be too large to decide about the compliance with regulations but cannot be quantified. PTB in Germany has investigated the problem for the German authorities by calculation, evaluation of Round-Robin-tests und large measurement series in model houses. The results are presented in the talk.
Field measurements of acoustic performance in buildings: a Round Robin Test
Authors: Scamoni Fabio , Bassanino Maurizio , Bruno Giuseppe , Zambon Giovanni
Published: May 2008

This paper presents the experimental results of a round robin test performed on the same building by different teams working with three independent bodies: a research body, ITC-CNR, a university laboratory DISAT and the Regional Agency for Environment Protection of Lombardy, ARPA. A partition wall (the airborne sound insulation between rooms), a floor (the impact sound insulation between rooms) and a façade (the insulation of the façade against outdoor sound) were tested, using the measurement methods given in the relevant parts of the ISO 140 series. The accuracy of acoustic measurement methods in buildings depends on many factors. In this round robin test, the situation (varying from straightforward rectangular rooms to half open spaces with all kind of shapes) and the construction details were kept fix. The analysis was aimed at investigating the influence of the operating condition of the equipment (repeatable settings) and the reproducibility, using different types of acoustic instrumentation and varying the method (choice of source and microphone positions). In particular the tolerance limits in the verification of the requirements of tender specifications were investigated.
Previous results on the evaluation of the influence of sound level meter case in diffuse field
Authors: Molares Alfonso R. , Sobreira-Seoane Manuel A.
Published: May 2008

In order to evaluate the influence of the sound level meter case on real measurements, two different case geometries are tested using Boundary Element Method. Solving the coupled structural-acoustic problem by means of an iterative procedure, their correction curves are obtained for various angles of incidence and for diffuse field. The deviation due to the case is obtained by comparison against the result of the reference microphone. The results reveal that the influence of the case can be relevant at the middle frequency range with deviations that can exceed 0.4 dB under free-field conditions for normal incidence. At the time of writing this abstract the available results show that the deviation for diffuse field at middle frequencies can reach 0.2 dB, although further research is needed to evaluate the deviation at higher frequencies.
Recent developments in modeling and measuring scattering from trabecular bone
Authors: Wear Keith A.
Published: May 2008

Laboratories at the US Food and Drug Administration, the University of Paris and elsewhere have investigated scattering from trabecular bone. Recent analysis of data from 23 human femur samples in vitro suggests that the Faran Cylinder Model and the Weak Scattering Model accurately predict frequency dependence of backscatter coefficient. Shear mode conversion of incident longitudinal waves may be a significant source of scattering loss. Other recent work involves the effect of errors of attenuation measurements on backscatter coefficient estimates. Backscatter measurements must be compensated for attenuation in order to estimate backscatter coefficient. However, attenuation is often overestimated because it is often measured using phase sensitive receivers that exhibit phase cancellation artifacts. Recent analysis of data from 16 human calcaneus samples in vitro suggests that backscatter coefficient estimates that are based on phase sensitive attenuation compensation tend to overestimate 1) average magnitude of backscatter coefficient at 500 kHz by a factor of about 1.6 ± 0.3 (mean ± standard deviation) and 2) average exponent (n) of frequency dependence by about 0.34 ± 0.12 (where backscatter coefficient is assumed to be proportional to frequency to the nth power).
Development of a simple and accurate approximation method for the Gaussian beam expansion technique
Authors: Liu Wei , Ji Peifeng , Yang Jun
Published: May 2008

The calculation of the sound field can be greatly simplified by using the Gaussian beam expansion technique. The source distribution function is expressed as the superposition of a small number of Gaussian functions, and the expansion coefficients could be obtained by minimizing an object function in the spatial or k-space domain. In this paper, a fast algorithm is developed to determine the Gaussian function coefficients for a more accurate approximation. Two-stage procedures are employed in the proposed method. Firstly, two real coefficients are estimated by a simple search approach, and then the least mean square (LMS) algorithm is adopted for determining the optimal expansion coefficients. Finally, the presented method is evaluated in the case of calculation of sound fields radiated from a piston and a rectangular planar source. Simulation results show that, compared with the previous approaches, the developed scheme is simple to implement with high accuracy.
Acoustic characterization of thin polymer layers for Love mode surface acoustic waveguide
Authors: Robert Laurent , El Fissi Lamia , Friedt Jean-Michel , Cherioux Frederic , Ballandras Sylvain
Published: May 2008

We investigate the use of thin (1-10 um) polymer films as guiding layer for Love mode surface acoustic wave sensors. Beyond the great gravimetric sensitivity provided by the polymer guiding layer resulting from the low acoustic velocity, the use of photoresists provide ecnonomical means of depositing guiding layers of optimal thicknesses compared to inorganic layer deposition processes (typically PECVD deposition of silicon dioxide lasting several hours). The limit of very thick (> 100 um) layers provides means of propagating interface waves mostly insensitive to the environment (package-less sensors) whose properties only vary through modification of the bulk properties of the polymer. We here analyse the evolution of the properties of the guiding layer in terms of acoustic velocity and losses as a function of time (solvent evaporation following photoresist spin coating) and temperature (typical baking steps). The polymer films is deposited on AT-cut quartz patterned with interdigtated transducers for generating 40 um-wavelength shear waves converted to a guided Love mode in a delay line configuration. We complete the experimental results with data interpretation using a model of acoustic wave propagation yielding quantitative results including viscosity and density out of the velocity and insertion loss measurements, both for the guided Love mode and interface layers