bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of non linear system identification methods : the example of non linear propagation of acoustic waves in ducts
Authors: Novak Antonin , Simon Laurent , Gilbert Joël , Lotton Pierrick , Kadlec Frantisek
Published: May 2008

The weakly non linear propagation of travelling acoustic waves in ducts is a well known problem leading to approximated analytical solutions. From an experimental point of view, the classical way for estimating the non linear parameters of propagation is to generate sine waves and to analyse the higher order harmonics as a function of the amplitude and the frequency of the excitation. In this work, new methods for estimating the non linear parameters of propagation are developed and compared to the sine excitation based method. The excitation signals associated to these new methods can be stationary noise or logarithmic chirps. For these excitation signals, the data processing is based on Multiple Input Single Output (MISO) direct path method. The comparison is made in terms of signal to noise ratio robustness and computation time. Experimental and theoretical results are also compared. We particularly show that a measurement using only one logarithmic chirp allows estimating accurate results for a broad band of amplitudes and frequencies. Associated computational time is then drastically reduced.
Operational Impacts of the Environment on Mid-Frequency Navy Sonar Systems In Shallow Water
Authors: Speckhahn Marcus M. , Lingsch Stephen C. , Fabre Josette P. , Garr Michael T. , Wetzel-Smith Sandra K.
Published: May 2008

The coastal oceans represent a challenging domain for mid-frequency maritime Anti-Submarine Warfare (ASW) sonar systems to operate effectively. Information on the advantages and disadvantages of, as well as general tactical employment criteria for the prevalent types of active mid-frequency sonar systems found in the world's navies is provided. Operational performance of these systems, which include hull-mounted sonars, monostatic buoys and multistatic active systems, as well as dipping sonars, is always affected by shallow water environmental parameters. These acoustic and oceanographic factors include frequent bottom interactions of the transmitted acoustic energy, highly variable sound speed and noise fields, strong coastal currents and high levels of acoustic clutter. Accurate and timely four-dimensional sensor performance predictions and optimization recommendations can mitigate some of the negative impact of the environment on sonar detection ranges. We discuss the trade-offs and assumptions made by modern computer-based tactical decision aids to deliver the most accurate environmental information balanced by the need to deliver these data in tactical time frames useful to the ASW mission planner and sonar operator at sea. We will also present thoughts on the quantification of acoustic uncertainty in support of ASW operations and the need for high-fidelity active sonar training systems.
Quantifying ocean acoustic sensitivity to environmental uncertainty/variability
Authors: Dosso Stan E.
Published: May 2008

It is well known that acoustic data used in sonar applications are strongly influenced by physical parameters of the ocean environment. Environmental sensitivity studies are often based on a qualitative comparison of acoustic fields computed for a reference environmental model and for a perturbed model in which one or more parameters have been changed. The acoustic-field perturbation generally includes a component representing a spatial shift of the field (i.e., local field structure remains coherent, but shifts in range and/or depth) and a component representing a change to the shifted field. Hence, the field change at a fixed point can indicate high sensitivity in cases where the field structure changes little but is simply offset, which can conflict with an intuitive understanding of sensitivity. This paper quantifies sensitivity rigorously in terms of a statistical measure of the relative uncertainty of acoustic fields or transmission loss due to realistic uncertainty/variability in environmental parameters. Further, accounting for field shifts can provide a more meaningful sensitivity measure for many applications. The sensitivity of acoustic fields to the state of knowledge of the sound-speed profile, bathymetry, and seabed geoacoustic parameters is examined for both range-independent and range-dependent cases. [Funded by DRDC-Atlantic Rapid Environmental Assessment Project.]
Fluctuation of mid-frequency propagation in shallow water
Authors: Tang Dajun , Henyey Frank S. , Williams Kevin L. , Rouseff Daniel , Dahl Peter H. , Wang Zhongkang , Quijano Jorge E. , Choi Jee Woong
Published: May 2008

As part of the ONR-sponsored SW06 experiment, mid-frequency sound propagation was measured at ranges 1-10 km in the frequency band of 2-10 kHz in August, 2006. The water depth is 80 m and the source depth is 30 m, close to the minimum of a duct with a thermocline above and a warm salty water below. The receivers are clustered into two groups, one at 25 m depth, the other at 50 m. The region has active internal wave activity during this time. Because the source is near the axis of the sound channel, it is observed that propagation is dominated by trapped modes and behaves similar to sound propagation in a deep water duct. Amplitude fluctuations and cross-frequency correlations are estimated. The scintillation index as a function of frequency and bandwidth is calculated.
In ocean evaluation of low frequency active sonar systems
Authors: Hjelmervik Karl Thomas , Sandsmark Geir Helge
Published: May 2008

Sonar performance measurements in the sea are always affected by uncontrollable and/or uncertain environmental conditions as sound speed variations, bottom topography or the acoustic properties of the sea floor. This paper presents a method to determine a sonar - target geometry which minimizes the uncertainty in target signal excess due to environmental variability. An acoustic model is used to estimate the signal excess for a large number of sound speed profiles measured in the relevant area. The results are compared seeking a target range and depth where the estimated signal excess is robust with respect to the variation of sound speed profiles to be expected in the actual area. Results from sea trials will be presented as well as simulated examples used to demonstrate the robustness or sensitivity of the signal excess to environmental changes at different test geometries.
Modeling higher order statistics of shallow water reverberation
Authors: Lepage Kevin D.
Published: May 2008

The modeling of the higher moments of shallow water reverberation is addressed for problems where non-Rayleigh reverberation is caused by scattering from rough boundaries with non-Gaussian height distributions. Expressions for the first three spatial moments of exponentially height-distributed roughness are derived for both Gaussian and exponential correlation functions corresponding to Gaussian or von-Karman second order spectra. The bi and tri-spectra for these roughness distributions are also derived, and differences are highlighted between these results and the results that are obtained for Gaussian height-distributed higher order spectra. Finally results for the higher moments of reverberation pressure are derived for exponentially height-distributed bottom roughness with the Gaussian spatial correlation function in the presence of multipath as a function of time, bandwidth, and correlation length scale. [Work supported by ONR]
Computational Predictions of sonar performance based on full wave acoustic propagation modeling
Authors: Wolfson Michael
Published: May 2008

For fishery acoustics, sonars offer the advantage of inferring the biomass of a given ocean volume at a lower operational cost of traditional echo-sounders, but wave guide effects which induce multi-pathing yield unknown variances in bio-mass estimates. A sonar performance model has recently been developed to assist in understanding this variance based on the para-axial approximation to the acoustic wave equation. The model takes into account the geometry of the sonar deployment (source depth, transmit/receive beam patterns, pulse shape) and the acoustic environment (water column and geo-acoustic bottom) and creates a data base of two-way transfer functions for a chosen set of range-depth cells. Then, given a hypothetical aggregation or school of fish, each with its own target strength, as well as noise and reverberation levels, one can create intensity maps which can be used to perform sensitivity studies to ascertain the performance characteristics of a fishery sonar. This talk will discuss the theoretical development of the model, its constraints, and provide an example which highlights its potential for future work. The example will be in a shallow water (100 m) environment using acoustic frequencies of around 10 kilohertz for imaging aggregations of pelagic fish. The Naval Ocean Partnership Program is gratefully acknowledged for this work.
Temporal and spatial coherence of low frequency acoustic modes in shallow water
Authors: Deferrari Harry , Nguyen Hien B. , Whylie Jennifer
Published: May 2008

Three recently collected shallow water acoustic propagation data sets have common experimental parameters of fixed sources with multiple frequency m-sequence transmissions, HLA and VLA receptions, and detailed measurements of the ocean acoustic environments. In each case, broad band signals allow the separation of modes by arrival time and the computation of spatial and temporal coherency for individual modes of propagation thus eliminating the effects of multipath interference. Here, coherency estimates are compared for several ranges from 10 to 80 Km and depths of 80 to 250 m, frequencies from 100 to 1600 Hz and for a wide range of potential energy levels of the internal wave field. There are a number of consistent findings. Low order modes are more coherent than high order modes in both space and time. Low frequency signals respond deterministically and in proportion to internal wave fluctuations whereas higher frequencies are randomized and have saturated statistics. In between, phase wrapping occurs. The number of bottom interactions is shown to be a critical factor in coherence especially for frequencies of 800 Hz and above. At very long ranges out of plane arrivals introduce multipath interference even for single mode reception.
Effects of internal waves on acoustic coherent communications during SW06
Authors: Song Aijun , Badiey Mohsen , Newhall Arthur , Lynch James F. , Deferrari Harry
Published: May 2008

During the SW06 experiment conducted east off the New Jersey continental shelf from July to September of 2006, internal wave surface expression and water temperature profiles were recorded when phase shift keying signals (PSK) were transmitted to study internal wave effects on coherent underwater acoustic communications at low to mid frequency bands. The collected communications data are processed using time reversal multichannel combining followed by a decision feedback equalizer. Due to the presence of internal waves, the acoustic channels show a time-varying property. Continuous channel updates prior to time reversal combining are required to combat fast channel fluctuations. The communications performance in terms of output signal-to-noise ratio exhibits significant change due to the internal waves. Further, the internal wave effects on the performance of coherent acoustic communications exhibit a frequency- and depth- dependency. The choices of receiver parameters also can be affected by the presence of internal waves.
Calibration of wideband systems, need for a standard
Authors: Zakharia Manell E.
Published: May 2008

Although wide band sonar system are becoming more and more popular, there is no unified standard method for their calibration. Most of the wideband systems are calibrated at multiple frequencies using single frequency methods. Although such calibrations give correct figures, these figures do not correspond to the real use of the systems and do not display properly the problems encountered while using such systems such as signal deformation due to the directivity pattern. For instance, the zeroes of directivity patterns that correspond to destructive interference at one frequency are spatially smeared even for a band of 10% and appear as spectral variations. We will show two examples of such calibration with increasing difficulty. The first case considers a wideband sounder covering two octaves (20-80 kHz) and the second one a parametric array (primaries around 100 kHz and parametric generation from 10 to 20 kHz). In the second case, the difficulty is increased due to the factor of about ten between the primary and the secondary frequencies that are also associated to important level difference (about 40 dB). It requires a high linearity constraint of the whole calibration chain.
Acousto-optic tomography for mapping of high-frequency sonar fields
Authors: Theobald Peter D. , Robinson Stephen P. , Hayman Gary , Koukoulas Triantafillos
Published: May 2008

This paper presents an acousto-optic method for tomographic mapping of acoustic fields generated by high-frequency sonar array transducers. The method uses a laser interferometer to measure the integrated refractive index change across the propagating acoustic wave generated by the transducer. An interferometer being a displacement or velocity measuring device, interprets this rate of change of optical path length as a displacement or velocity. Obtaining a series of these projections by scanning the laser beam or the transducer for a number of rotation angles of the transducer allow a two-dimensional plane of the acoustic field to be reconstructed using the techniques commonly used in X-ray Computed Tomography. Acousto-optic tomographic measurement results are presented for a 95 by 95 mm, 400 kHz 1-3 composite, 4 element sonar array transducer and are compared to conventional planar hydrophone scans obtained using a 1.5 mm probe hydrophone. The optical method allows measurement of the acoustic field without perturbing the field being measured, which can occur when using the planar hydrophone scanning method. Different tomographic geometries are considered, including parallel beam and fan-beam methods, with the advantages and disadvantages of each being discussed.
Robust Adaptive Vector Sensor Processing
Authors: Poulsen Andrew J. , Baggeroer Arthur B. , Kitchens Jonathan Paul , Watson Jennifer A.
Published: May 2008

A sizable literature exists on the theory of processing signals for many vector sensor array applications. In practice, however, mismatch and several noise processes can pose significant problems. If adaptive beamforming is also used, the "snapshot" issue potentially increases by a factor of four since each element in a vector sensor array consists of a scalar hydrophone and up to three spatially orthogonal particle motion sensors. Both of these sensor types have very different response and noise characteristics. Particle motion sensors are more sensitive to non-acoustic, motion-induced noise than hydrophones. In towed line array configuration, those sensors orthogonal to the direction of motion are exposed to higher intensities of flow noise at low frequencies than those coincident to the array axis. Similarly, different dipole sensors may be exposed to varying degrees of rotational mismatch. Sensors may also rest on the seafloor, creating asymmetries. Physical constraints also relate pressure and particle velocity measurements via conservation of momentum and mass equations. We examine adaptive processing methods customized to the unique characteristics of vector sensors. Array gain and other performance metrics in the presence of system mismatch and uncertainties is presented using common ocean noise models, including directional jamming, isotropic and surface noise.
Measurement of total sound energy density in enclosures at low frequencies
Authors: Jacobsen Finn
Published: May 2008

Many acoustic measurements rely on determining the total sound energy in an enclosure; and this quantity is usually estimated by measuring the mean square pressure at a number of discrete positions. Almost 30 years ago it was shown theoretically that the normalised spatial variance of the total sound energy density (potential and kinetic) is one third of the normalised spatial variance of the potential energy density (the mean square pressure) in a reverberant sound field above the Schroeder frequency. About ten years later this prediction was confirmed experimentally. However, until recently measurement of the total sound energy density (in air) has required an elaborate arrangement based on finite different approximations using at least four matched pressure microphones; therefore the method has never come into use. However, with the advent of a three-dimensional particle velocity transducer it has become somewhat easier to measure total rather than only potential energy density in a sound field. This paper examines the spatial uniformity of potential, kinetic and total sound energy density in enclosures theoretically and experimentally with particular emphasis on the frequency range below the Schroeder frequency.
The Viscous-Grain-Shearing (VGS) theory of wave propagation in marine sediments
Authors: Buckingham Michael
Published: May 2008

The grain-shearing (GS) theory of wave propagation in a marine sediment is based upon the idea that, as grains slide against one another, the dissipation becomes progressively stronger, a phenomenon known as strain hardening. The GS theory predicts a sound speed showing weak, logarithmic dispersion and an attenuation that scales linearly with frequency. At frequencies above about 10 kHz, such behavior matches the sound speed and attenuation data obtained during the SAX99 experiment in the Gulf of Mexico. But at lower frequencies, the measured dispersion curves show a lower sound speed and higher attenuation than predicted by the GS theory. A generalized version of the GS theory, designated the VGS theory, takes account of the effective viscosity of the molecularly thin layer of pore fluid between contiguous grains, which limits the degree of strain hardening that can occur during sliding. The VGS dispersion expressions are the same as those of the GS theory, except for the appearance of a simple algebraic function that has an effect only at low frequencies, below 10 kHz. The resultant VGS curves match the sound speed and attenuation measurements from SAX99 over the measurement frequency band from 1 to 400 kHz. (Research supported by ONR.)
Bistatic scattering in sediments: comparison of model and scaled tank experiments at 238 kHz
Authors: Howey Russell , Blondel Philippe
Published: May 2008

Multiple-aspect scattering is increasingly used to investigate seabeds and objects, buried or not. However, high-frequency scattering processes on/in sediments need to be better understood, particularly when the structure and/or composition of these sediments is not fully homogeneous. Scaled tank experiments were conducted using the University of Bath facilities. A narrow acoustic beam (10° beamwidth) was generated by a transducer resonant at 238 kHz, imaging a silt seabed at 45°. Scattering angles varied between ̃16° and ̃70° (50 distinct values); bistatic angles varied 40° either side of in-plane with a 2.5° step (33 distinct values). Bottom returns were picked through two methods (automatic and manual) and converted into scattering strengths, accounting for the size of the scattering patch. This large dataset has been compared with the model of Jackson and Williams for bistatic scattering, intended for 10-100 kHz but successfully tested at 240 kHz by other workers. Recursive fitting of model parameters to the experimental values shows the influence of sediment variations (backed by microscopic measurements of actual grain size distributions) and the importance of even small tilts in the surface of the sediments. These results can be used to test the validity of extending this scattering model to higher frequencies.
Dispersion and attenuation due to scattering from heterogeneities in the frame bulk and shear moduli of sand sediments
Authors: Hefner Brian T. , Jackson Darrell R. , Calantoni Joseph
Published: May 2008

Previously, we presented the results of applying perturbation theory to the problem of fast compressional wave propagation through a Biot medium with heterogeneities in the frame bulk modulus (B. T. Hefner et al., J. Acoust. Soc. Am. 119, 3447 (2006)). It was found that the heterogeneities scattered energy into both the slow and fast compressional waves, thus increasing the attenuation of the fast compressional wave. This theory has since been generalized to account for heterogeneities in both the frame bulk and shear moduli. For the fast compressional wave, energy is now scattered into the shear wave as well as the fast and slow compressional waves, further increasing the attenuation of the coherent field. While shear wave propagation is unaffected by variations in the frame bulk modulus, scattering does occur when there are heterogeneities in the shear modulus. Energy in the shear wave is scattered into both shear and compressional waves as well. The generalized theory depends on the autocorrelation functions of both the shear and bulk moduli variations as well as the cross-correlation function between the moduli. Efforts are underway to estimate these statistics in simple random packings of spherical grains using discrete-element modeling. [Work supported by ONR.]
Data-model comparisons for broadband sound speed and attenuation in sandy seabed
Authors: Zhou Ji-Xun , Zhang Xue-Zhen
Published: May 2008

Sound speed and attenuation in sandy seabed were analyzed and reviewed from low-frequency (LF) acoustic measurements, conducted at 18 locations in different coastal zones around the world. [Zhou and Zhang, JASA 117(4), 2494 (2005) and 119 (5), 3447 (2006)]. The resultant sound speed and attenuation in a frequency range of 50-2000 Hz in sandy bottoms can be described equally well by the Biot-Stoll poro-elastic model, the Chotiros BICSQS model [JASA 116(4), 2011-2022 (2004)] or the Buckingham VGS model [JASA 122(3), 1486-1501(2007)]. The geophysical parameters were inverted from the best match between the LF data and each of these three geo-acoustic models. The values of the inverted geophysical parameters were reasonable based on both theoretical considerations and published experimental measurements. A combination of the LF field-inverted data with data from the SAX99 experiment and other recent high-frequency measurements offers a broadband reference data set of sound velocity and attenuation for sandy bottoms in shallow water over a frequency range of 50-400,000Hz. The data-model comparisons show that, with one set of adjustable input parameters, all three geo-acoustic models may perfectly match either the broadband velocity dispersion or broadband attenuation, but not both. These models generally either underestimate dispersion or overestimate LF attenuation. [Work supported by ONR.]
Role of heterogeneity for sound speed and attenuation in unconsolidated ocean sediments
Authors: Berryman Jim G. , Pride Steven R.
Published: May 2008

Although ocean sediments may have many types and degrees of heterogeneity, it has been determined that two-component models are tractable for poroelastic, thermoelastic, and thermoporoelastic studies. We have found in particular that a substantial part of the increased sound wave attenuation observed in both ocean sediments and laboratory glass-bead experiments above 50 kHz can be explained by such a two-component poroelastic model. Furthermore, the inclusion of thermal expansion and entropy effects into a generalized binary thermoporoelastic model provides an additional attenuation enhancement (though not as large --- by itself --- as the poroelastic enhancement) of a mathematically very similar type that is also relatively easy to model and understand. The paper will present this extended model as well as comparisons to available data.
Auditory brainstem responses in birds: How well do they compare to behavioral techniques for assessing hearing
Authors: Brittan-Powell Elizabeth , Lohr Bernard , Noirot Isabelle , Dooling Robert
Published: May 2008

Behavioral methods are the gold standard for assessing hearing sensitivity in birds. In many cases, however, behavioral techniques are simply impractical. The non-invasive auditory brainstem response (ABR) represents perhaps the next best approach, and researchers are increasingly turning to the ABR to obtain estimates of hearing sensitivity, auditory system function and development. Our lab has evaluated hearing sensitivity in over 11 species of birds using the ABR, and for six of these species, we have also obtained auditory thresholds by behavioral conditioning methods. These data, along with other results from the literature on bird hearing, now allow general conclusions about the use of ABR as a tool for measuring auditory sensitivity in birds. Waveform morphology is highly conserved across orders of birds. Regardless of how threshold is defined, the ABR audiogram reliably reflects the frequency range of hearing and the shape of the behavioral audiogram. However, ABR thresholds are higher than behavioral thresholds by 20-30 dB but with some variation across species. Aside from audiograms based on simple detection thresholds for tone bursts, ABR methods in birds have also been useful in assessing auditory development, hearing impairment, recovery of function with hair cell regeneration, masked thresholds and aspects of spectral and temporal processing.
The Auditory Brainstem Response (ABR) Across Mammalian Species
Authors: Burkard Robert
Published: May 2008

The auditory brainstem response (ABR) has been reported in a variety of mammalian species. I have published ABR studies in mammalian species including humans, gerbils, cats, rats, bats, and mice. In many cases, the non-human work was designed to extend observations made in humans. I will discuss data that addresses the variability in the slope of the ABR latency/intensity function across animal species. I will compare ABRs in humans and in gerbils to stimulus manipulations such as click level, click rate, noiseburst risetime and level of masking noise. I will discuss the effects of high stimulus rates across age in the kitten/cat, and compare this to reports in humans from the literature. I will end by discussing my views of the advantages as well as the challenges of using animal models when interested in human normative or pathologic processes.
Arbitrary evoked potentials: using AEPs to measure hearing in fishes
Authors: Mann David , Hill Randy
Published: May 2008

Auditory evoked potential (AEP) techniques have become commonly used to measure hearing of a wide variety of animals. However, there is no standard way of defining a threshold from auditory evoked potential data. There are two arbitrary factors affecting the precision of AEP data: the number of sweeps averaged together to detect the AEP, and the method of calculating a threshold from the AEP data. While these arbitrary factors do not invalidate comparative studies where these variables are standardized, different laboratories use different techniques. We describe sources of variation in estimating thresholds using evoked potential techniques using the goldfish as an example. There was little variation in AEP thresholds due to variation in electrode placement or in the method of arbitrarily assigning an AEP threshold. The largest variation was due to differences in the number of sweeps averaged. Under controlled conditions using the same goldfish in the same test tank with the same number of sweeps averaged, AEP's better predicted behavioral thresholds at high frequencies than low frequencies. Since averaging reduces uncorrelated background noise (neural and electrical), it should theoretically be possible to obtain AEP measurements below behavioral thresholds with enough sweeps averaged together.
On the dynamics of the clavichord
Authors: D'Alessandro Christophe
Published: May 2008

The clavichord is generally considered as the most sensitive and subtle among keyboard instruments. The player/instrument interaction is very direct: the mechanism is reduced to as simple lever, allowing for a direct contact between the finger and string through the key. Key velocity, two string-tangent contact signals, radiated acoustic signal have been synchronously measured for about 10 dynamic nuances and all the notes of four instruments (a 51 notes unfretted instrument, after a German XVIIIth century model, a 51 notes fretted instrument after Hubert (1754), a 45 notes fretted instrument, after a German XVIIth century model, a 37 notes fretted instrument after a medieval model). The instruments can be portrayed in terms of dynamic range, tonal/spectral colour and sound decay time. As for the dynamics, there is some evidence for a linear relationship between sound pressure level and the velocity of the tangent; and an almost constant spectral richness independently of loudness (in contrast with e.g. the piano). A simple model of the tangent/string interaction is proposed. This model reproduces well the behaviour of experimental data, and it may explain why sound quality of the clavichord depends much on the player's ability.
What have they done to the Strads
Authors: McLennan John , Wolfe Joe
Published: May 2008

Almost every baroque violin, including those of Stradivarius etc, was extensively modified during the conversion to the romantic or modern configuration. What were the acoustic and playing changes? To answer this question, independently of the confounding factors of wood and manufacture, a baroque violin was made and subjected to acoustic and playing tests, before and after (i) replacement of the neck and fingerboard with longer, heavier more inclined parts, (ii) replacing gut with modern nylon-cored strings. Other changes were also made, including bridge style and position, bass bar and soundpost sizes and bow used. Loudness (Saunders plot) was not greatly changed, except for the E string with a long string length. Some acoustic features survived the changes, and professional baroque and modern style players reported that the instrument preserved some of its "personality". Comparisons were made with modern gut strings used by professional baroque players. As well as the acoustic differences, player assessments of bright/dull, full/thin, open/closed, ease of response, evenness, dynamic range are reported. Averaged over all ratings, the players ranked the romantic set up slightly better than the baroque (78% vs 71%).
Perceptual studies of violin vibrato
Authors: Fritz Claudia , Woodhouse Jim , Moore Brian , Cross Ian
Published: May 2008

Although it seems obvious to violinists that vibrato has a large influence on the perception of violin tone quality, published studies of violin vibrato have mainly concerned its influence on the sound from a scientific point of view, i.e. the characterisation of its time-frequency properties. Work will be described to explore the link between the perception of vibrato notes, the extent of frequency modulation and the level of damping of the resonance modes of the violin. Damping influences the "peakiness" of the frequency response function. The test methodology is based on liveliness ratings and triadic comparisons, where subjects have to select the most similar and the most different pair in each triad (presentation of three sounds). The sounds of the corpus are synthesised using sawtooth waves with frequency modulation, whose amplitude is varied, filtered through a set of admittances corresponding to a reference violin and two modified violins, one with the damping of all modes increased, the other one with the damping decreased.
Shaping and understanding sound: Violin makers, musicians and scientists from Renaissance to Romantism
Authors: Houssay Anne
Published: May 2008

The training of instrument-makers in Renaissance Italy is linked to a rediscovery of theoretical works on physics and sound as well as to some new tools and skills. Then, the development of physics in the seventeenth and eighteenth century lead the establishment of acoustic as a modern science, with the distinction of partials from harmonics. The "western world" has given explanations on vibrations, modes and then elasticity theories, some of which have been included into general knowledge. By times, links between scientists and makers have developed and have participated to the development of musical instruments. Traditional violin makers are craftspeople, and they construct instruments by choosing step by step between many possibilities from the drawing of the model and the choice of materials, to the cutting out of the shapes to create air volumes and vibrating facings. Their parameters are the dimensions, shapes, weight, elasticity, quality and duration of sounds and notes. The test for judging the results is the playing of the instrument by a very competent musician. We will explore, with a point of view of the historian of techniques how the meeting of different cultures and knowledge have transformed the instruments from the Renaissance to the begining of the 19th century.
Analysis of the timbre of Slovak folk reed aerophones using source-filter model
Authors: Rusko Milan
Published: May 2008

Bagpipes are the only group of traditional folk reed instruments that have survived in Slovak folk culture until now. Unlike Scottish highland pipe, gaita, cornemuse etc., all the types of Slovak bagpipes use single reeds in both chanters and drones. Moreover the horns of the drones are partly closed with a plate having only a small opening for air output and sound radiation. This forms a Helmholz-like resonator - acoustic filter having a strong influence on the acoustic and aesthetic properties of the sound. The ideal of the sound timbre of these pipes is "less open" (compare to open and closed vowels in speech) and, in spite of its relatively high loudness, "less agressive" in comparison to pipes with open horns. This paper presents our approach to study the ideal of sound timbre of the Slovak bagpipe using a source-filter all-pole model. To identify resonance frequencies/formants, we applied inverse filtering technique using discrete linear prediction. Some properties of the source (reed) were studied using parameters like amplitude qutient and open quotient. The possible relations between timbre of speech sounds (vowels) and the timbre of the sound of musical instruments are discussed.
Computing Number of People Awakened by Aircraft Operations Noise
Authors: Miller Nicholas P.
Published: May 2008

The acoustics literature documents a number of field studies in which aircraft noise was measured in people's bedrooms while their awakening was simultaneously monitored. Nearly all the field studies produced a dose-response relationship between noise and an awakening response. These dose-response relationships generally show good agreement with each other. Virtually without exception, however, these dose-response relationships pertain to (1) the indoor noise dose produced by a single aircraft flyover and (2) the chances that the noise dose will awaken an average person. These dose-response relationships are too limited for application to a full night of operations and to a realistic population of varying individual sensitivities to noise-induced awakenings. The dose-response relationships do not account for multiple aircraft exposures during the night or for person-to-person variation in how deeply different people sleep. This presentation first briefly reviews a method previously reported for applying the study data to a full night of operations, accounting for time of night and for individual sensitivity to awakening. It then compares percent of population awakened for realistic situations, and shows the effects of including or excluding time of night or individual sensitivities to awakening.
Noise and health in the Greater Rotterdam Area
Authors: Wolfert Henk
Published: May 2008

In the Greater Rotterdam Area a second study to Noise and Health has been carried out in 2007 and 2008. In 2003 a first study was carried out and that study reported that around 12 percent of the people living in the Greater Rotterdam Area were highly annoyed by noise mainly caused by traffic. The number of people sleep was disturbed and suffered high blood pressure were reported and amounted to 6 percent for sleep disturbance and 3 percent were suffering hypertension. The 2003 study took place within the regularly framework of the Rotterdam Regional Council of Governments Environmental Monitoring program, a program that reports yearly the environmental performance indicators in the Greater Rotterdam Area. Beside this yearly report a theme report is published. Last year's theme reports were published about Air Quality and Energy. In 2007 the board of this program decided that in 2008 the theme should be Noise and Health. The 2008 study is not only an update of the 2003 study but is more detailed and more comprehensive as well, and based on recent insights in health effects, caused by long lasting noise too.
Implementation of ISO 1996-2 (2007) pure tone assessment in a sound level meter
Authors: Greene Charles , Manvell Douglas , Scholz Matthias , Enggaard Anne Lin
Published: May 2008

Noise can be said to be tonal if it contains a distinguishable, discrete, continuous note. This may include a whine, hiss, screech, hum, etc., and any such subjective finding is open to discussion when reported. This is important when it is considered that the likelihood of a noise-provoking complaint depends on its relative level to background, and whether or not it has certain audible characteristics. Fortunately, ISO 1996-2 (2007) provides objective FFT (engineering) and 1/3-octave band (survey) assessment procedures to be used to verify the presence of audible tones if their presence is in dispute. Brüel & Kjær has implemented the methodology of ISO 1996-2 in relation to assessing the audibility of prominent discrete tones in environmental noise into its innovative 2250 and 2270 hand-held analysers. This paper describes the implementation in hand-held instrumentation.
On the use of linear aero-acoustic models
Authors: Abom Mats
Published: May 2008

The classical theory of aero-acoustics is based on Lighthills acoustic analogy which essentially leads to a wave equation with a source term defined by the flow field. This source term is assumed unaffected by the acoustic field and the resulting model can be seen as a linear model which, e.g., for duct acoustic problems can be formulated as an acoustic multi-port. Such linear aero-acoustic models can be applied to most aero-acoustic problems occurring in engineering practice with the exception of whistling, i.e., situations where the source term is affected by the acoustic field. At KTH this methodology has been applied to a number of applications over the years ranging from cooling and ventilation fans to flow generated noise from ducted orifices (valves) and air terminal devices. In this paper the experience from these works is summarized and the experimental techniques developed at KTH to characterize linear aero-acoustic sources are described. Recent efforts to extract linear aero-acoustic models from numerical calculations are also addressed.
Amplitude distribution of magnetoelastic waves propagating in a vortex field in a superconducting layer
Authors: Maruszewski Bogdan T. , Drzewiecki Andrzej , Starosta Roman
Published: May 2008

Magnetic field enters the type - II superconducting body along a discrete arrangement of magnetic vortex lines. In the dynamic case when the magnetic field vary in time, around each such a line a supercurrent flows. So, the vortices interact one to another with the help of the Lorentz force forming this way a new mechanical field of elastic properties. Moreover, those lines arrange themselves in a triangular or quadratic lattice. Such a set is observed if the intensity of the applied to the material magnetic field is close to its lower limiting value. The paper aims at investigating amplitude distributions of magnetoelastic waves propagating solely in the vortex field of the superconducting layer. Our attention have been focused on the applied magnetic field intensity influence on those amplitudes for various wave frequencies.
Nonlinear ultrasound fields simulation of harmonics from exponential and bessel beams sources
Authors: Jakjoud Hicham , Chitnalah Ahmed , Aouzale Noureddine , Kourtiche Djilali
Published: May 2008

It's well known that the harmonic imaging quality can be improved by using sources that radiate narrower and attenuated sidelobe beams. Hence we try to enhance the harmonics' cartography by studying different source's power distributions. We developed a numerical code, using the spectral method, in order to resolve the parabolic wave equation. The numerical results are compared to those given by other researchers in order to validate our algorithm. Two source's power distributions (exponential and Bessel beams) are studied and compared to the uniform case. The use of exponential source leads to harmonics diagrams without sidelobes neither nearfield oscillations. But the beam width is increasing with propagation. The Bessel source presents a limited diffraction beam. The beam width is almost constant throughout the nearfield and the transition zone. The sidelobes have a weak level in the fundamental curves and they don't appear in the second harmonic ones.
The effect of a speech target's motion on its recognition in the presence of simultaneous competing sentences
Authors: Grantham Wesley , Ricketts Todd , Ashmead Daniel
Published: May 2008

Prior knowledge of where to listen significantly improves speech recognition of target sentences presented in the presence of distracter sentences coming from different locations [G. Kidd et al., J. Acoust. Soc. Am. 118, 3804-3815 (2005)]. The present study extended the work of Kidd et al. by measuring the effect of a target's motion on its recognition when competing messages are present. In an anechoic chamber normal-hearing subjects were presented with three simultaneous sentences from the CRM corpus and were instructed to indicate key words from the target sentence (identified by a call-sign previously known to the subject). In the stationary condition the three sentences came from -60°, 0°, and +60° azimuth. In the moving condition, the target source moved during its on-time (e.g., from -60° to 0°) while the two distracter sentences were stationary (e.g., at ±60°). In both cases, subjects either knew in advance where the target would be (Certain Condition) or did not know (Uncertain Condition). It is hypothesized that motion of the target will result in a release from informational masking. That is, the detrimental effect of location uncertainty observed with the stationary targets will be reduced or eliminated when the target is moving.
Potentiation of noise-induced hearing loss by aviation fuel exposure in rats
Authors: Fechter Laurence D. , Gearhart Caroline A. , Fulton Sherry , Kim Yoon Hwan
Published: May 2008

Clear standards have been established for workplace noise. These are designed to protect workers against noise-induced hearing loss. That occupa-tional hearing loss still occurs despite such standards may reflect a variety of issues ranging from enforcement of standards, to adequacy of standards, and problems of noise assessment. An additional factor that influences susceptibility to noise-induced hearing loss is the presence of chemical contaminants in the workplace that render the auditory system especially vulnerable to noise. We report on the ability of aviation fuels to potentiate noise-induced hearing loss in laboratory rats. Subjects were exposed to JP-8 jet fuel, a synthetic fuel produced from coal using the Fischer-Tropsch method, or to clean air. Half of the subjects received a moderate noise exposure following fuel or air exposure. The noise exposure was designed to produce a temporary threshold shift. JP-8 + noise produced greater disruption of distortion product otoacoustic emissions as well as the auditory threshold than did noise alone. Supported by VA Rehabilitation Service grants and the American Petroleum Institute.
Effects of boundary tones on accent-related F0 peak alignment
Authors: Shue Yen-Liang , Iseli Markus , Shattuck-Hufnagel Stefanie , Veilleux Nanette , Jun Sun-Ah , Alwan Abeer
Published: May 2008

Speakers sometimes delay the F0 peak of a high accent beyond the accented syllable (Silverman and Pierrehumbert, Papers in Laboratory Phonology I, 1990; Xu, Phonetica, 2001). Previous studies of factors affecting peak alignment focused on the phrasal position of the accented word and the segments of the accented syllable (Jilka and Möbius, Interspeech 2007). Shue et al. (Interspeech 2007) hypothesized that if an accented word also contains boundary tones, that could influence the position and height of the F0 peak. A test corpus controlling for vowel type, syllable number and position of the focused word, based on the utterances "Dagada gave Anne a dada (daily)" and "A dada gave Anne dagadas (daily)", was produced using four prosodically different contours, involving high (H*) and low (L*) pitch accents on either "dagada" or "dada", in declarative and interrogative forms eliciting different boundary tones. Analysis of five repetitions spoken by four male and four female native American English speakers reveals that for most speakers, the presence of boundary tones on the target word shifts the accent-related F0 peak earlier when other factors are held constant. Preliminary results suggest effects of boundary tone on H* F0 peak height as well.
How prosody correlates with syntax: An observation on Sakizaya, an endangered Formosan language
Authors: Chen Sally , Shen Wen-Chi , Sung Li-May , Fon Janice
Published: May 2008

This pioneering study investigates the relationship between prosody and syntax of Sakizaya, an endangered Formosan language in eastern Taiwan. Both elicitation data and spontaneous data were collected from five informants (aged 48 to 74), in order to provide a more thorough sketch on this VSO language with clear case marking and voice systems. Preliminary results showed that in descriptive sentences, prosodic units and syntactic units do correlate with each other, depending on which of the four voices is used. (The four voices in Sakizaya: agent-, patient-, instrumental, and locative voices) However, once specific functions are imposed onto a sentence, they will override this "default" setting, and adopt corresponding prosodic patterns for the ease of communication. For example, in this language, the default position to receive a nuclear accent should be the ultimate syllable of a sentence; however, we observed an accent shift onto the penultimate syllable for yes/no questions, exclamations, as well as continuously progressive sentences. In negation sentences, pitch peaks are distinctively higher in the accented syllable of the negator (which posited sentence-initially), instead of the ultimate syllable in sentence-final position. Lastly, case markers and voice markers were found as preferred positions for speech planning and repair.
Characterization of targets buried in disordered medium
Authors: Belkebir Kamal , Ashraf Faheem , Saillard Marc , Chaumet Patrick
Published: May 2008

We consider in this paper the problem of the determination of the permittivity profile of an unknown buried object from measurements of the electromagnetic scattered field. The target under test is assumed to be buried in one of the two involved media while the sources and the receivers are located in the other medium (limited-aspect data configuration). This ill-posed and non-linear inverse scattering problem is reformulated as an optimization problem that is solved iteratively. This method consists in building up a sequence of the parameter of interest by minimizing, at each iteration step, a cost functional representing the discrepancy between the data and those that would be obtained with the best available estimation of the parameter. In addition, when clutter is present, the decomposition of the time reversal operator method is used to improve the signal-to-clutter ratio, since it allows us to synthesize a wave that focuses on the scatterer. The data associated with this incident field are included in the iterative minimization procedure.