bluuebunny/crossref_metadata_2025 huggingface dataset:
Close coupling or points of rendezvous? Connections between intonational events and the segmental grid
Authors: Mixdorff Hansjörg , Pfitzinger Hartmut , Werner Stefan
Published: May 2008

The authors examine the connection between the fundamental frequency (f0) contour and the segmental grid, employing the Fujisaki model for decomposing an f0 contour into phrase and accent components. As shown in earlier work by the first author, accent commands are closely connected with the accented syllables of the constituent words of an utterance. They reflect the temporal alignment of intonational gestures by their on- and offset times, as well as the magnitude of the gestures by their amplitudes. Their timing relates to phonemic function, and the amplitudes are strongly correlated with the prominence of an accented syllable. In this study the authors attempt to model the intensity contour of an utterance as a concomitant of the articulatory gesture, namely by low-pass filtering pulse-wise "syllable commands", yielding onset and offset points as well as amplitude values of the syllabic gestures and relate these data to the accent command data from the f0 tier. We examine the influence of phonemic distinctions on the alignment between the f0 contour and the segmental grid, as well as the influence of the intonational gesture on the realization of segments. The work is carried out on spontaneous American English speech data from the Buckeye corpus.
Lexical stress information modulates the time-course of spoken-word recognition
Authors: Reinisch Eva , Jesse Alexandra , McQueen James M.
Published: May 2008

Segmental as well as suprasegmental information is used by Dutch listeners to recognize words. The time-course of the effect of suprasegmental stress information on spoken-word recognition was investigated by tracking Dutch listeners' looks to arrays of four printed words on a computer screen as they listened to spoken sentences. Each target was displayed along with a competitor that did not differ segmentally in its first two syllables but differed in stress placement (e.g., 'CENtimeter' and 'sentiMENT'; capitals marking stressed syllables). The listeners' eye-movements showed that suprasegmental stress information is used to recognize the target before distinct segmental information is available. Furthermore, the presence of initial-syllable stress affected the degree to which words compete for recognition: Targets with non-initial stress ('sentiMENT') suffered from stronger competition than initially stressed targets ('CENtimeter'). Follow-up experiments showed that initial-syllable duration, as a cue to lexical stress, is not interpreted dependent on the speaking rate of the preceding carrier sentence. This still held when other stress cues like pitch and amplitude were removed. Rather, the speaking rate of the preceding carrier affected the speed of word recognition globally, even though the speaking rate of the target itself was not altered.
Using pause durations to discriminate between lexically ambiguous words and dialog acts in spontaneous speeech
Authors: Dhillon Rajdip
Published: May 2008

Using multiparty conversations conducted in spontaneous Scottish English speech, this study examines whether pause durations can be used to discriminate between lexically ambiguous words pertaining to different dialog acts and, more generally, whether pause durations signal different types of dialog acts. Dialog acts describe the pragmatic functions of utterances and their detection requires attention to pragmatic function, syntax, prosody, surrounding context, and interaction between speakers. In this study, the dialog acts examined are 'floor grabbers', which are used by speakers to gain attention or to interrupt a current speaker who has the floor, and 'acceptance/agreements', which express agreement to or acceptance of a previous speaker's question, proposal, or statement. Experiments 1 and 2 examine pause durations following the lexical items 'right' and 'good' respectively when used as 'floor grabbers' or 'acceptance/agreements'. Experiment 3 examines pause durations following 'floor grabbers' and 'acceptance/agreements', regardless of the lexical item. Results of all three experiments indicate that pauses following 'floor grabbers' are significantly longer than those following 'acceptance/agreements'. This study shows that pause durations are in fact a reliable means of discriminating between lexically ambiguous words and distinguishing dialog acts. The study also sheds light on how stable pause usage is in spontaneous speech.
Evaluation of phonetic constraints in acoustic-to-articulatory inversion
Authors: Laprie Yves , Potard Blaise , Bonneau Anne
Published: May 2008

The objective is to evaluate phonetic constraints intended to guarantee the phonetic realism of vocal tract shapes generated by an articulatory model, i.e. here that of Maeda. The constraints are based on the relation between vocal tract shapes allowed for a vowel and formants frequencies of the vowel. They are speaker independent since they are derived from standard phonetic knowledge. We used them to reduce the number of solutions in acoustic-to-articulatory inversion. The impact of constraints has been investigated by comparing vocal tract shapes recovered by inverting five French vowels /i, e, a, u, y/ to those obtained by outlining articulator contours in X-ray images. To that purpose we used X-ray images (used by Maeda to elaborate his articulatory model) with the corresponding speech signal. The evaluation shows that unrealistic vocal tract shapes are penalized by constraints, that vocal tract shapes recovered through inversion are in very good agreement with X-ray images and that relevant articulatory variability is recovered when considering all vocal tract shapes corresponding to one vowel. These constraints thus complement the articulatory model very efficiently. Additionally, the inversion framework complemented by phonetic constraints is an efficient way of investigating the acoustic properties of an articulatory model.
Temporal Organization of the Compounds in Standard Chinese
Authors: Zee Eric , Lee Wai-Sum
Published: May 2008

The study investigates the temporal organization of the bisyllabic, trisyllabic and quadrisyllabic compounds in Standard Chinese. Results of the analysis of the speech data from six speakers show that (a) the rime durations, the durations of the syllable-initial voiceless fricatives and the VOT of the syllable-initial voiceless aspirated stops and affricates are conditioned by the position of the component syllable in the compounds; (b) the rime duration decreases as the component syllable moves from the final toward the initial position in the compounds; (c) the mean duration of the rimes is longer in the final position than in the initial and medial positions; (d) the voiceless fricatives and the voiceless aspirated stops and affricates are shorter in the medial position than in the initial and final positions; (e) the cross-speaker variation is less in the rime duration than in the duration of the voiceless fricatives and VOT of the voiceless aspirated stops and affricates; and (f) no temporal patterns have been observed in the voiceless unaspirated stops and affricates. The results will be discussed in terms of articulatory programming and timing (Kozhevnikov and Chistovich, 1965; Allen, 1975). A temporal model of the compound production in Standard Chinese will be proposed.
A comparison of planar projection and time reversal techniques
Authors: Clement Gregory
Published: May 2008

Planar projection methods, such as the angular spectrum approach, have been shown to rapidly relate fields between two planes in space/time, with only a single measurement plane needed to characterize an entire field. Variants of the method have been used for medical transducer characterization, as well as for HIFU treatment planning. Presently, a potential advantage of the approach is considered: Operating in the temporal frequency domain, backward planer projection (i.e. "space reversal") is invariant with respect to the spatial dimension, even in the presence of anomalous dispersion. This ability can be contrasted with time reversal, which is violated in the presence of the absorption term. Time reversal is compared with planar back-projection under a varying set of conditions, including the presence of dispersive and nonlinear homogeneous and heterogeneous media. The specific case of a simulated impulsive signal from a 30-cm diameter piston radiator is directed through a 50-cm section of a tissue-like medium (B/A = 5 to 7, c = 1480 to 1600 m/s, ρ = 0.9 to 1.1 gm/cm3, α= 0.5 to 2 db/cm/MHz) over a range of pressures. Ability of backward projection to restore initiating signals is verified, provided that significant signal levels of all relevant frequencies can be reached at the initial plane.
Ultrasonic transducers for imaging and therapy based on time-reversal principles
Authors: Sarvazyan Armen
Published: May 2008

Focusing of ultrasonic waves is a fundamental aspect of most of the medical applications of ultrasound. There are three approaches in focusing acoustic energy: geometrical, using concave transducers and acoustic lenses, electronic, using phased arrays, and time-reversal (TR), which allows both spatial and temporal concentration of acoustic energy. The aim of this talk is to make comparative analysis of advantages and disadvantages of ultrasound focusing techniques, demonstrate unique capabilities of TR focusing in medical imaging, surgery and therapy. Examples of embodiments of ultrasonic focusing transducers utilizing TR method for various biomedical applications will be presented. TR ultrasonic transducers are comprised of a reverberation chamber, which could be either an aluminum block or a water filled volume of irregular shape, and one or several piezotransducers attached to or incorporated in the reverberator. Optimization of the TR transducers for a particular application is considered, including the geometry of the TR reverberator, shape, type and dimensions of the piezotransducers. Unique abilities of TR transducers to steer the focal spot in 3D, produce pulses with arbitrary waveforms in a wide frequency band and generate focal regions of arbitrary predefined shapes using simple means such as single channel system with one piezoelement will be demonstrated.
Guiding of HIFU beams towards optical contrast agents by time-reversal of photoacoustic waves
Authors: Bossy Emmanuel , Aubry Jean-François , Funke Arik R. , Fink Mathias , Boccara Albert-Claude
Published: May 2008

This presentation will discuss the opportunity to use photoacoustics to guide high-intensity focused ultrasound (HIFU) in biological tissue. The photoacoustic effect consists in the emission of sound by an illuminated optically absorbing region, based on the thermoelastic expansion following the absorption of a light pulse. In the near-infrared range (700 nm to 900 nm), the absorption of light in biological tissue is relatively low, and multiply scattered photons can travel as deep as a few centimetres in tissue. Photoacoustic waves can therefore be generated deep in tissue, and have recently been used in vivo to perform passive acoustical imaging of optical absorbing features, such as blood vessels. We recently demonstrated on tissue-mimicking phantoms that photoacoustics could be coupled to time-reversal to automatically focus ultrasound towards an optical absorber [Bossy et al., APL 89(18), 2006]. We propose to further develop this approach to automatically guide HIFU therapy beams towards a targeted region labelled with an optically absorbing contrast agent. This presentation will discuss various aspects of such an approach, based on modelling and experimental results.
Time Reversal Acoustic focusing using layered membranes structure
Authors: Sinelnikov Yegor , Vedernikov Andrey , Sutin Alexander , Sarvazyan Armen
Published: May 2008

In the recent years numerous Time Reversal Acoustic Focusing Systems (TRA FS) employing various reverberation chambers ("acoustic cavities") accumulating acoustic energy in time were described in the literature. We propose an alternative reverberator composed of a liquid-filled volume comprising a series of spatially distributed membranes with varying thickness in the range from one quarter to half wavelength of ultrasound. Random spatial variation of ultrasound reflection from such membranes leads to randomization of acoustic field that highly improve Time Reversal focusing of the system. A theoretical model of reflections from nonuniform membranes is suggested to evaluate spatial and temporal characteristics of TRA focusing formed as a result of numerous reflections and reverberation of ultrasound propagating though the plurality of membranes. The dependence of focal structure and focused waveform was investigated for suggested structure and their focusing efficiency has been compared with that of the conventional reverberators. In the experiment, the membrane were made of Polyethylene Terephthalate or Nylon thermoformed films. Ultrasonic signals were radiated by transducers with frequency in the range from 3 to 10 MHz. Experiment demonstrated effective TRA focusing by membrane arrangement that can be used for ultrasound focusing and steering in various minimally-invasive biomedical applications.
Wavelet filter bank based wide-band audio coder
Authors: Nováček Jan
Published: May 2008

New system for wide-band audio signals compression is presented. The system is based on a two stage wavelet filter bank principle. Special psychoacoustic model was designed for the system. Data compression is nowadays very topical issue. Due to the development of information technologies more sophisticated compression algorithms may be designed. Most of the present compression systems, e.g. MPEG, ATRAC or Vorbis, use a simple filter bank or DCT transformation. Both methods suffer from the origin of undesirable artefacts which are disturbing for the sound perception. Wavelet filter bank is used to suppress these artefacts and to increase data compression. Frequency dependant windowing function is used for improve of frequency resolution at low frequencies along with faster response at high frequencies. Wavelet transformation based coding algorithm can improve temporal masking effects over conventional perceptual coding algorithms for data compression.
The Use of Mel Cepstral Coefficients and Markov Models for the Automatic Identification, Classification and Sequence Modelling of Salient Sound Events Occurring During Tennis Matches
Authors: Hunter Gordon J. , Zienowicz Krzysztof , Shihab Ahmed I.
Published: May 2008

Some significant events in sports matches occur too quickly to be detected by conventional video. Audio signals, normally sampled at a much higher rate, provide a way to detect such short events. Here, we employ methods used in automatic speech recognition - templates of Mel Frequency Cepstral Coefficients (MFCCs) over several adjacent time windows, with Principal Components Analysis (PCA) - to identify and classify sound events : different tennis strokes, ball bounces, echos, speech and applause, occurring during tennis matches. Excellent success rates were achieved for both event detection ( 97.74 %) and correct classification (on average 98.64 % across all classes) of 1504 sound events in the available recordings. The successful classification rate varied between classes but no class had a success rate below 94%. This could be valuable to spectators, officials and coaches in tennis and other sports - including cricket, baseball and golf - or to make video games (such as the Nintendo Wii) more realistic. We also model sequences of these events in both discrete (event oriented) and continuous time domains, using Markov and other models, to give our system predictive as well as reactive capability, help identify "unusual" or "unexpected" salient sounds and hopefully improve the correct classification rate for the classes where the performance was weakest.
3D Gabor analysis of transient space-time waves
Authors: Martinez Loic , Wilkie-Chancellier Nicolas , Glorieux Christ
Published: May 2008

Laser generation/detection methods allow the investigation of ultrasonic transient phenomena in both space and time dimensions. Used for the experimental investigation of surface wave propagation along a two dimensional medium, laser ultrasonics leads to three dimensional (3D) space-time signal collections. In order to extract the wave propagation information, the classical high resolution signal processing methods or 3D Fourier Transforms are not suitable to identify the transient and local aspect of wave propagation and mode conversion. In order to quantify these transient aspects in the Space-Time-Wave number-frequency domains, the 3D Gabor transform and some other suitable methods are presented. Their potential for the identification of the local and transient complex wave numbers is illustrated with the propagation of Lamb waves on a plane limited plate. The experimental results are in good agreement with the numerical simulations.
Computer learning method for scattering junction identification
Authors: Kestian Adam , Roginska Agnieszka
Published: May 2008

Acoustic reflectometry is a non-invasive, time-domain method of identifying the geometry of an acoustical space. A sound pulse is injected into a space and the resulting impulse response details particular changes of impedance, which is a result of a cross-sectional area change or an elbow/T- intersection. Each cause of reflection, known as a scattering junction, has a distinct reflection contour. Previous works were able to identify these scattering junctions via algorithms that attempt to extract particular contours from the impulse response. In the present study, the prominent reflections of the space are observed, isolated, and then compared to a training database of all possible scattering junctions. This method eliminates the necessity to create a contour identification algorithm, as scattering junctions are defined based on its most similar neighbors in the training database. Preliminary results suggest that this computer-learning algorithm can successfully identify reflection contours of a space with varying cross-sectional areas from those that were stored in the training database, which suggests that this method could be a more efficient and versatile alternative to previous identification processes.
Tools and techniques to measure environmental parameters that improve mid-frequency sonar performance predictions
Authors: Osler John C. , Pecknold Sean , Hines Paul C.
Published: May 2008

The performance of mid-frequency active sonar systems in littoral waters depends upon several environmental factors and their variability in space and time. These factors include seabed scattering strength, bottom loss, and the water column sound speed profiles. DRDC Atlantic has developed experimental apparatus and techniques to measure these environmental parameters in order to enhance the accuracy of sonar performance estimates in the mid-frequency band, 1 to 10 kHz. Experiments have been conducted during sea-trials on the Scotian Shelf and Strataform area on the New Jersey Shelf. In some instances, these experiments have been in conjunction with international research partners to provide an inter-comparison between experimental techniques and/or a comparison of rapid environmental assessment techniques with more traditional, and time-consuming, methods. In this talk, we will demonstrate that predictions of sonar system performance improve when the environmental parameters obtained with these techniques are used, rather than parameters from archival sources.
A comparison of methods for approximating acoustic uncertainty in underwater sound channels
Authors: James Kevin R. , Dowling David R.
Published: May 2008

The accuracy and reliability of acoustic field calculations are often determined by uncertainty in environmental parameters. There are currently several approaches for predicting calculated-acoustic-field uncertainty arising from environmental uncertainties. This presentation outlines the current development of a method for predicting acoustic uncertainty based on correlations between variations in an uncertain parameter and spatial shifts within a calculated acoustic field. The results of this technique are compared with several other modern methods for predicting acoustic uncertainty such as direct sampling of environmental parameters, linearization and higher-order finite difference approaches, the adjoint method for approximating derivatives of the acoustic field with respect to environmental parameters, and polynomial chaos methods. The advantages and limitations of each technique are presented for range-independent shallow-ocean sound channels at nominal ranges of 1 to 10 km and frequencies from 100 Hz to 1 kHz. Comparisons of accuracy, computational speed, and applicability to particular uncertain parameters and field prediction routines are provided. Emphasis is placed on identifying the types of sound channel properties and environmental uncertainties for which each technique performs most reliably, as well as identifying situations for which current techniques are not yet adequate. [Sponsored by the Office of Naval Research, Code 321OA].
Comparison of sonar transmission models at mid-frequency for synthetic and real environments
Authors: Jones Adrian D. , Sendt Janice S. , Duncan Alec J. , Clarke Paul A. , Zhang Zhiyong , Vu Han
Published: May 2008

The suitability of sonar transmission loss models for application to the mid-range of acoustic frequencies has been studied by comparing the outputs from a number of models. Emphasis has been placed upon the requirements for models for circumstances relevant to both continental shelf and deep ocean zones within the Australian region. In particular, the ability to describe transmission in surface ducted environments for a deep ocean, and in a shallow ocean with both ducted and downward refracting environments has been considered. For the deep ocean case, a synthetic environment was selected, and the ability to describe duct trapping was examined. For the shallow ocean case, scenarios selected for comparison correspond with ocean tracks for which environmental parameters had been collected and received sound pressure time series measured. The subject transmission loss models are from a variety of types. To enable the most valid comparison, input parameters have been matched across models to the fullest extent. This paper presents the state of progress of this work, including a comparison of models amongst themselves and, for continental shelf scenarios, against measured transmission loss.
Effects of volume and boundary variability on the statistics of received signal frequency
Authors: Joseph Jeremy , Culver Richard Lee , Jemmott Colin W.
Published: May 2008

The overall goal of our research is to incorporate statistical knowledge of received passive signal variability and uncertainty into the signal processing. To accomplish this goal we need to better understand the sources of this variability, which are due in part to propagation through the ocean channel. Propagation introduces significant variation in received signal parameters through rough surface and bottom scattering as well as volume inhomogeneities. This talk focuses on the variability introduced by these sources and its effect on the statistics of the frequency spectrum of the received signal. We consider low frequencies, for which theoretical predictions are compared with PE-based simulation results. Work supported by ONR Undersea Signal Processing Code 321US.
Measuring the equivalent beam angle of echo sounders with split-beam transducers
Authors: Andersen Lars Nonboe , Ona Egil , Pedersen Geir , Tichy Frank , Lunde Even Borten
Published: May 2008

When trying to measure the numerical density of marine animal populations with scientific echo sounders, several technical system parameters are determined through a standard-target calibration. The acoustic scattering properties of standard targets are known a priori. In a typical standard-target calibration the system gain and the transducer beam pattern are estimated. The system gain parameter is used both when measuring volume backscattering strength and when measuring target strength. The calibrated beam pattern is currently used only for target strength estimation. However, measurements of mean volume backscattering strength also require knowledge of the effective sampling volume of the acoustic beam, namely the equivalent beam angle. This parameter is typically not determined during an ordinary echo sounder calibration. A method for measuring the equivalent beam angle and the transducer angle sensitivity of a specific split-beam transducer is described, and results from exemplary calibrations are presented. Changes in the calibration parameters as a function of environmental parameters, especially the sound speed in water, are discussed.
Prediction for the acoustic field of a high frequency cylindrical transducer
Authors: Xia Tiejian , Wang Yuebing , Zhou Lisheng , Liu Qiang
Published: May 2008

The BEM software is implemented in the prediction of the acoustic field produced by a cylindrical transducer, the transducer consists of 1200 PZT pillars which are fixed on the surface of a 156-mm-diameter and 120-mm-height cylinder. The acoustic field around the transducer is measured at the frequency 120kHz using an optical vibrometer, the measured data are fed into the BEM software as the boundary condition, and the directivities of the transducer are forecasted in the vertical and horizontal planes. To verify the calculation, the acoustic field in the far field of the transducer is measured using a hydrophone, and good agreements between the prediction and the measurement convince that the BEM software can be used to predict acoustic fields of cylindrical transducers through distributions of acoustic fields measured in their near fields.
Acoustic vector sensors and vector/tensor processing in ocean acoustics research
Authors: D'Spain Gerald
Published: May 2008

Several passive sensor systems that simultaneously measure acoustic pressure and the three components of acoustic particle motion have been designed and deployed in seagoing experiments by the Marine Physical Lab over the past two decades. Descriptions of these sensor systems and results from applying various signal/array processing methods with these data are presented in this talk. Although vector sensors do not provide any additional information on the sound field than that obtained by a suitable number of properly placed hydrophones, they do provide estimates of the sound field's directional properties from a very compact package. Applications where available space is severely limited include autonomous underwater vehicles (AUV). Recent results from acoustic vector sensors installed in a flying wing underwater glider and inside a prop-driven AUV to quietly measure sounds in the ocean illustrate the benefits, and drawbacks, of the use of vector sensors on autonomous platforms. The extension of the signal/array processing approaches to tensor sensors indicates the promise of additional gain, if the sensor design challenges can be overcome. [Work supported by the Office of Naval Research].
Using acoustic streamlines to visualize energy flow across boundaries
Authors: Chapman David M.F.
Published: May 2008

For spherical waves that radiate from a point source in a homogeneous fluid and propagate across a plane boundary into a dissimilar homogeneous fluid, the acoustic field may differ significantly from the geometric acoustics approximation if either the source or receiver is near the interface (in terms of acoustic wavelengths) or if the minimum-phase path is near the critical angle. Cross-boundary energy flow from a continuous-wave point source is visualized by tracing acoustic streamlines: those curves whose tangent everywhere is the average acoustic intensity vector. It is seen that the acoustic energy flow is not always in line with the "Snell's law" or minimum-phase ray path. Also, acoustic energy streamlines do not display unusual behaviour in the vicinity of the critical angle. Finally, it is shown that there exists a law of refraction of acoustic energy streamlines across density discontinuities, analogous to Snell's law of refraction of ray paths across sound speed discontinuities. Examples include water-to-seabed transmission and water-to-air transmission. [Work supported in part by ONR Code 32]
On the usefulness of waterborne measurement of particle velocity in geoacoustic inversion
Authors: Hermand Jean-Pierre , Smith Kevin B.
Published: May 2008

Recent advances in sensor design have led to the development of receiving systems whose elements are vector sensors, i.e., sensors that simultaneously measure the acoustic pressure and fluid motion due to the propagation of acoustic energy at the sensor location. As such, arrays of vector sensors can provide more information about the sound field than arrays made of traditional hydrophones, and thus are attractive for various applications including the inversion for environmental properties. The fundamental question addressed by this paper is: does the use of acoustic vector data versus pressure-only data improve the results of an inversion scheme based on waterborne observations and matched field processing? To our knowledge no experimental data are available yet to allow a detailed comparison of performance between standard (pressure-only) arrays and vector sensor arrays for environmental inversions. For a preliminary study we will simulate the inversion of vector sensor data in the South Elba environment for which pressure-only inversion results and ground truth data are available following the Yellow Shark'94 and Blue Planet'07 experiments. Broadband signals received on fully-populated and sparse arrays will be considered.
Characterization of the Near Scattered Acoustic Vector Field
Authors: Barton Robert , Smith Kevin B.
Published: May 2008

In this study, we investigate the properties of the scattered acoustic vector fields generated by simple geometric objects, including the infinite rigid plate, disk, and sphere. Analytical solutions are derived from acoustic target strength scattering models in the near field region. Of particular interest is the understanding of the characteristics of energy flow of the scattered acoustic vector field in the near to far-field transition region. We utilize the time and space separable instantaneous active and reactive acoustic intensity to investigate the relative phase properties of the scattered field. Numerical results are presented for the near region scattered acoustic vector field of simple objects in both two and three dimensions.
Use of dual methods to infer methane bubble populations in gassy sediment: Inversion of propagation data
Authors: Robb Gary B. , Leighton Timothy G. , Mantouka Agni , Best Angus I. , Dix Justin K. , Humphrey Victor F. , Klusek Zygmunt , White Paul R.
Published: May 2008

The inversion of the acoustic properties of gassy sediments presents the optimum manner of determining the in situ distribution of sediment-based methane bubbles. An in situ device that measures both compressional wave attenuations and combination-frequency components in gassy sediment lying within 2 m of the seabed has been developed at the University of Southampton. This device was deployed at an inter-tidal site along the South coast of England. Compressional wave attenuations were measured from 10 to 100 kHz though the analysis of propagation signals transmitted from a variety of sources to a buried co-linear hydrophone array, with propagation distances spanning 0.5 to 2 m. Measured attenuations were inverted to infer in situ bubble size distributions using both established and new acoustic models for gassy sediment. The analysis and results of the combination-frequency component are described in a companion paper.
Shape optimization of polygonal rooms for a correct modal distribution at low frequencies based on psychoacoustic criterion
Authors: Floody Sergio , Venegas Rodolfo
Published: May 2008

Resonances in small rooms may lead to inadequate frequency responses. In rooms, where the exigencies on the listening conditions are important, these resonances may cause non wanted coloration effects, which implies a non desirable sound quality. By choosing the right shape and dimensions it is possible to reduce the audible effects of these resonances. The presented methodology aims to determine the shape and size of small and medium polygonal-shaped rooms based on the finite element method for modeling the physical acoustic behavior of the room; a neural network for loudness estimation and genetic algorithm for estimating the optimal dimensions. A comparison with previous techniques used to choose the dimension of rectangular room is also presented.
The reflected sound field by curved surfaces
Authors: Vercammen Martijn
Published: May 2008

Many spaces have curved walls or ceilings. With improved building technology and new fashions in architecture (blobs) there is an increasing number of problems due to the acoustic reflections by these surfaces. Sound reflected by concave surfaces will concentrate in a narrow area. In practical applications of room acoustics these curved surfaces will be calculated with mirror imaging or ray tracing programs, in which the structure is modeled by flat segments. Alternative is a geometrical approach. Both methods do not correspond to reality. The only valid calculation method is the calculation from a wave extrapolation method. It is shown that a theoretical correct solution of the sound field by curved surfaces is possible. A fairly simple expression for the sound pressure in the focal point is found and a more complicated description of the reflected sound field by small curved surfaces is presented. With these results the sound field in field applications can be calculated.
Calculation of temporal evolution of sound pressure levels in rooms, based on diffuse reflection
Authors: Gamba René , Cazard Guillaume , Senat Claude
Published: May 2008

This paper describes a model which enables the temporal evolution of sound pressure levels in rooms to be calculated. It is built on the assumption that sound waves are totally scattered when reflected by the walls. This model prescribes the sampling of all the surfaces of the room and defines a process of time discretization, process which enables the temporal evolution of energetic exchanges between each sample to be known. Ultimately, the model allows the sound pressure level to be calculated in every point of the room for each time sample Δt (echograms). Thanks to the echograms, some useful criterias for room acoustic studies can be evaluated : reverberation time, EDT, D50, C80,... Measurements and calculations have been carried out for different kinds of rooms. We will describe them in the second part of this paper.
Sound reduction of open noise screens
Authors: Hardlooper Jan
Published: May 2008

Open noise screens consist of vertical absorbing screens with a depth of 1 meter, placed perpendicular to a building with a mutual distance of 1 meter. The screens are placed at a distance of approximately 1,5 meter. Open noise screens combine a sound reduction of 16 dB with a very open character for ventilation and daylight admittance. Measurements are carried out on a scale model (1:40) in a laboratory and in situ on a real size mock-up, built in a 40-ft container. The results of the mock-up are comparable to the laboratory results. Frequency analysis shows the acoustical principles of the screens and the influence of several parameters. A calculation model is developed tot predict the results for other configurations. The principle of open noise screens is successfully applied for 200 new dwellings in Amsterdam. Suggestions are given for applying open noise screens near highways and railroads, instead of traditional closed screens.
False killer whale hearing adjustment during echolocation measured with evoked potentials
Authors: Nachtigall Paul E. , Supin Alexander Y.
Published: May 2008

While much has been previously learned about the echolocation performance and characteristics of the outgoing signals of echolocating dolphins and small whales, we have measured hearing using evoked potentials during echolocation. We have found that: (1) the whale may hear her loud outgoing clicks and much quieter returning echoes at comparable levels, (2) the whale has protective mechanisms and hears her outgoing signals at a level about 40 dB lower than similar signals presented directly in front of her, (3) when echo return levels are lowered either by making the targets smaller or by placing the targets farther away - without changing the levels of her outgoing signals, the hearing of those echoes remains at almost the same level, (4) if targets are made much smaller and harder to echolocate, the animal will increase what she hears of her outgoing signal - as if to heighten overall hearing sensitivity to keep the echo level hearable, and (5) the animal has an active 'automatic gain control' mechanism in her hearing based on both forward masking that balances outgoing pulse intensity and time between pulse and echo and active hearing control. Overall, hearing during echolocation appears to be an actively changing process.
Temporal resolution in the hearing system and auditory evoked potentials
Authors: Beedholm Kristian , Miller Lee A.
Published: May 2008

A popular type of investigation with auditory evoked potentials (AEP) consists of mapping the dependency of the envelope following response to the AM frequency. This results in what is called the modulation rate transfer function (MRTF). The physiological interpretation of the MRTF is not straight forward, but is often used as a measure of the ability of the auditory system to encode temporal changes. It is, however, shown here that the MRTF must depend on the waveform of the click-evoked AEP (ceAEP), which does not relate directly to temporal resolution. The theoretical relationship between the spectrum of the ceAEP and MRTF is such that the MRTF should be identical to the ceAEP if a 1/f weighting is applied to the ceAEP. Deviations from this relationship indeed reflect temporal resolution capabilities. We measured this in a harbour porpoise. Our devised stimulus was a sequence of 0.5 ms Hann weighted 130 kHz tone pips presented at an increasing rate (chirped) over a time span of 32 ms. The results reveal that the system's responsiveness declines roughly exponentially as a function of click rate with a rate constant of about -0.7 kHz and appears more rate limited than implied by traditional MRTF.
Performance comparison of violins through experimental force analyses
Authors: Ravina Enrico , Silvestri Paolo , Lowenberger Federico
Published: May 2008

The paper describes the most recent experiments developed on violins with different mounting (baroque, classical, modern) and specifically oriented to the dynamic forces analysis in significant points of the instruments. The vibrational behaviour of the soundboards are strongly influenced by the dynamic forces transmitted from the bridge: they are related also to the tension of the strings. An original testbench conceived to forces measurement has been set up: tensions on strings, forces detected under the bridge and deformations on the fingerboard and on the tailpiece are, in particular, monitored by means not intrusive thin-film tactile pressure measurement devices, micro load cells and micro strain gauges. Mapping of forces and strains are acquired in real time playing the instrument; the paper reports comparisons between differently mounted violins, playing notes under different techniques: continuous ("tenuta") , ghost ("strappata"), "detachet". Experiments are developed using different kind of strings (bowels, metallic,...). The results are used as input for experimental dynamic analyses and tests of the soundboard: in addition, they can be correlated to the acoustic response of the instrument.
Individual reed characteristics due to changed damping using coupled flow-structure and time-dependent geometry changing Finite-Element calculation
Authors: Bader Rolf
Published: May 2008

The vibration of a reed of a saxophone is calculated using a 2D model of the mouth cavity, the mouth piece and the reed. The time-dependent Finite-Element calculation takes the flow-structure interaction into account and changes the geometry of the flow according to the reed vibration in time. The model is used to study the flow behaviour, pressure distribution, reed vibration and reaction to disturbances of the system. A constant pressure is assumed at the mouth cavity to simulate the pressure of the player's lungs. During the time-dependent process, an impulse is modeled at the end of the mouth piece travelling back from the end of the tube. The damping of the reed was changed to study the reed behaviour. Hard damped reeds show a simple and stable impulse behaviour causing a clear pressure impulse. When the damping is decreased, the impulse coming back from the end of the tube causes the reed not only to open and close but also to show additional vibrations caused by the interplay of the reed's eigenfrequencies and the pressure acting on the reed. These are more or less independent of the travelling impulse and so are a sound characteristic of the reed itself independent of the played note and used articulation.
The influence of the mean flow on the transmission properties of wind instruments
Authors: Da Silva Andrey R. , Scavone Gary
Published: May 2008

The influence of mean flow on the transmission properties of wind instruments has traditionally been neglected due to the range of Strouhal numbers in which this family of instruments normally operate. However, this topic has gained considerable interest among the musical acoustic community during the last decade due to the appearance of new outcomes in research on duct acoustics. Nevertheless, very few contributions have investigated the effect of the mean flow on the transmission properties by taking into account the physical characteristics and dynamic peculiarities of wind instruments. The goal of this work is to present a numerical investigation of the influence of the mean flow on the end correction and on the magnitude of the reflection coefficient for different geometries and Strouhal numbers normally found in wind instruments. The results suggest that, excepting for a few cases, the mean flow can indeed be neglected and the aforementioned transmission properties can be described by the quiescent flow theory.
Numerical investigations of the bassoons aeroacoustic
Authors: Richter Andreas , Grundmann Roger
Published: May 2008

Solving the compressible, unsteady Navier-Stokes equations allows us to track single traveling waves in conjunction with a nonuniform superposed mean flow. Significant physical phenomena like wave steepening, viscothermal losses and acoustic streaming can be investigated. This may be helpful to understand the acoustical characteristics of different geometries, especially in musical woodwind instruments. Since acoustic perturbations are usually small compared to the driving pressure, the solution demands high-order accuracy and appropriate boundary conditions. We present a collection of our numerical results based on two- and threedimensional simulations of the aeroacoustic behavior inside the bassoon. This includes both simulations of the whole instrument under real playing conditions and also numerical studies of subsections of the instrument like tone holes. Here especially viscothermal effects are analyzed. Nonlinear effects like acoustic streaming which is primarily present in the crook of the instrument are also investigated and discussed. Flow field measurements based on Particle Image Velocimetry and pressure measurements inside and outside the instrument are performed to validate the earned results and show a good agreement between measurements and numerical results.
Effects of a hearing aid noise management feature on user perception and performance under noise
Authors: Ronsse Lauren M. , Wang Lily M.
Published: May 2008

This paper presents the effects of a hearing aid noise management feature on user perception and performance under noise. Hearing-impaired subjects were exposed twice to seven different noise signals which simulate common mechanical system noise, once with the noise management feature enabled and once disabled. The seven noise signals vary in terms of level and spectral quality, but are all within the range of background noise conditions found in commercial offices. Performance is gauged on three types of tests (math, verbal and typing), while subjective perception is measured via a subjective questionnaire. The results of this investigation will show if the hearing aid noise management feature reduces detrimental effects caused by background noise. Additionally, the data from hearing-impaired subjects are compared to those from normal-hearing persons to assess if significant differences are present between the two groups. If so, they may lead to the development of different standards for noise criteria levels in spaces designed for the hearing-impaired. [Work supported by a Univ. of Nebraska Layman Award and an ASHRAE Graduate Student Grant-in-Aid]
Prominent tones in noise - Proficiency testing among 30 laboratories of the ISO 1996-2 Annex C method and its predecessors
Authors: Pedersen Torben Holm
Published: May 2008

Since 1979 the Danish Environmental Protection Agency's Reference laboratory for noise measurements have arranged proficiency testing for the around 30 approved Danish laboratories that are measuring environmental noise. Many of these "comparison measurements" have included objective analysis of the prominence of audible tones according to the Joint Nordic Methods which are the predecessors and very similar to the method described in ISO 1996 part 2 Annex C. This paper gives examples on (computerized) analyses of the samples from these proficiency tests and states the uncertainties that can be expected when a number of laboratories with different experience and different types of equipment analyze the same samples. The samples will be available for future reference and can be downloaded from DELTA's homepage.
Issues in the evaluation of the tonality of nonstationary sounds containing time- varying harmonic complexes
Authors: Davies Patricia , More Shashikant R.
Published: May 2008

Nonstationary sounds that contain broadband noise and tone complexes whose fundamental frequency varies with time are encountered frequently. Aircraft flyovers and machines shifting operating speeds are examples. The tonalness of such sounds is a factor in how annoying they are. Most metrics used to quantify the tonalness of sounds have been developed for stationary sounds and are based on an analysis of spectra. Contributions from individual sinusoids are estimated and either summed or the maximum is taken. When sounds vary, spectral estimation can be problematic due to the conflicting needs to reduce the variance of the estimate, maintain high frequency resolution, and generate spectra at a rate where the varying tonal behavior can be tracked sufficiently. Harmonic complexes are often perceived holistically, having one dominant pitch, thus treating sinusoidal components independently and summing may not be appropriate. Tests conducted to analyze the tonalness of harmonic complexes in noise are described, and an analysis of aircraft flyovers is used to illustrate the issues that need to be addressed when estimating the tonalness of complex time-varying sounds.