bluuebunny/crossref_metadata_2025 huggingface dataset:
Strategic Noise Mapping of the City of Ljubljana, Slovenia
Authors: Štimac Alan , Globevnik Aleš , Stipanicev Dinko , Kuhelj Lilijana
Published: May 2008

Currently Ljubljana is the only agglomeration according to the definition of the directive 2002/49/EC in Slovenia. For this agglomeration, separate noise maps not only for road and rail traffic but also for industrial sources were made. As for the first phase of preparation there is no precise methodology stated for representing industrial noise sources in strategic noise maps regarding END and following the vision of other EU countries, only industrial plants classified as IPPC installations were taken into consideration of noise mapping. Short term noise measurements around industrial plants conducted according to ISO 1996 during previous three years were used as reverse engineering techniques for the determination of sound power levels of industrial plants. Elaboration of road and rail traffic noise maps required development of perfect acoustical model with 3D terrain modelling including all possible obstacles (barriers, walls, bridges, viaducts, etc.). For calibration of noise maps more then 30 measurements were performed following the standard DIN 45642. During all stages of elaborating noise maps, quality assurance procedures were performed with a view to estimate accuracy of the results. Strategic noise maps of the agglomeration performed at municipal level of Ljubljana will be used mainly for drawing up action plans and spatial planning of areas with different noise levels allowed.
Activated Resonance Systems as Silencers and Sound Absorbers
Authors: Leistner Philip
Published: May 2008

A great variety of classical resonance systems is used for sound absorption and attenuation in technical systems. Apart from other requirements such as minimum size, high reliability and low costs the acoustic efficiency can be fulfilled in a wide range. However, the performance is limited and focused on a certain frequency band. These restrictions can significantly be overcome by activation. A very clear system comprises a membrane (mass) and a rear air volume (spring) which can be assembled by using a conventional loudspeaker in front of a cassette. Even the 'passive' system is causing a respectable sound attenuation also at low frequencies. The activation is based on a microphone close to the membrane the signal (according to the exciting sound pressure) of which is linearly amplified and fed back to the loudspeaker. A lot of details have to be considered prior to the real applicability of such an activated resonator. But the remarkable benefits can be documented for numerous practical scenarios. Theoretical and experimental results are based on a sophisticated model of the resonant structure and its acoustic environment. Additionally, several practical challenges, e.g. the presences of turbulent air flow or high temperatures, can be solved by using specific modifications.
The use of communication device in background noise
Authors: Toppila Esko , Airre Pekka , Olkinuora Pekka
Published: May 2008

Communication devices are used more and more often in industrial premises. We have evaluated how the users experience these device in a call center (N=41), in a low noise warehouse (N=67) and in a noisy (L>80 dB) warehouse (N=25). For all subjects the same questionnaire was sent. The questionnaire contained questions were about the quality of communications device and self-evaluated hearing symptoms. The self-evaluated speech intelligibility was lowest in the high background environments. Still in the call center five persons and five in the silent warehouse had great difficulties with speech intelligibility. All these persons evaluated that they have always difficulties when communicating with people. In the noisy environments this relationship was not found. The need to rise the voice was highest in the warehouses ad did not depend on the background noise. Tinnitus was more frequent among process industry workers. The results suggests that lowered hearing function cause problems in low background noise. The self-evaluated nuisance depends on the complexity of the communication. The quality of the communication channel may also play a vital role in the communication problems especially for workers with hearing problems.
Research into the improvement of the management of helicopter noise in the UK
Authors: Waddington David C. , Kendrick Paul , Kerry Geoff , Muirhead Matthew , Browne Ray
Published: May 2008

Helicopter noise has a negative impact on the quality of life for many people. Effected populations are not just those living close to heliports, but include those exposed to noise from helicopters used by emergency services, the military, and commercial companies. One problem identified in the UK is that it is often difficult to complain about helicopter noise, since it is unclear which organisation is responsible for dealing with the complaint. Consequently, the Department for Environment, Food and Rural Affairs (Defra, UK) has commissioned research to summarise the following: i. the nature and extent of the concern about helicopter noise in the UK. ii. rules and regulations governing operations. iii. existing procedures for handling complaints. This stage of the project will produce a detailed report into the improvement of the management of helicopter noise. Also to be produced is a short non-technical guide including the means of redress for perceived disturbance. This paper will report on the findings of this project. [Work funded by Defra, UK]
Numerical modeling of transient poroelastic waves in the low frequency range
Authors: Chiavassa Guillaume , Lombard Bruno , Piraux Joel
Published: May 2008

A numerical method is proposed to simulate the propagation of transient poroelastic waves across heterogeneous media, in the low frequency range. A velocity-stress formulation of Biot's equations is followed, leading to a first-order differential system. The latter is splitted in two parts: a propagative one discretized by a fourth-order ADER scheme, and a diffusive one solved analytically. Near sources and interfaces, a space-time mesh refinement is implemented to capture the small scales of evolution of the diffusive slow compressional wave. Lastly, an immersed interface method is implemented to accurately model the jump conditions at interfaces between the different media. Numerical experiments in one and two dimensions are shown, with porous/porous or fluid/porous interfaces. Comparisons with analytical solutions confirm the efficiency of the approach. [1] G. Chiavassa, B. Lombard, J. Piraux, Numerical modeling of 1-D transient poroelastic waves in the low-frequency range, soumis au J. Comput. Appl. Math., (2007), disponible sur http://hal.archives-ouvertes.fr/hal-00193103/fr/
On the scattering of a plane wave by porous sound-absorbing strip
Authors: De Bruijn Alex
Published: May 2008

The analysis concerning the scattering of a plane wave by a porous sound-absorbing strip embedded in an infinite sound-hard surface is most relevant for the evaluation of measurements with respect to absorbing materials tested in a reverberation room. This diffraction phenomenon around the edges leads to an additional sound absorption, the so-called edge effect. This extra absorption can be analyzed and computed - among other well-known methods - by using a spatial Fourier field expansion just on the absorbing strip. The field in the space above the reflecting surface can be put into a contour integral of an angular spectrum in the complex plane or -in other words- a superposition of plane waves with complex angles of incidence. Matching both field representations leads to the solution of the unknown coefficients of the Fourier expansion and hence to the amplitudes of the total diffracted field. It would be interesting to compare these results with diffraction data obtained via an alternative technique: the Finite-Difference Time-Domain method using the direct Euler equations, also within the porous sound-absorbing material. The paper will show the data for the field amplitudes obtained by both methods and will discuss the agreement and differences.
On the influence of the micro-geometry on sound propagation through periodic array of cylinders
Authors: Venegas Rodolfo , Umnova Olga
Published: May 2008

Sound propagation in rigid porous media has been widely studied by using macroscopical models. These models make use of averaged quantities in which the microscopic details of the porous media geometry are represented by macroscopical parameters and, in a certain way, the influence of the microscopic geometry is not directly identified. In this paper, homogenization theory and finite element method are used for solving the full microscopic dynamic flow and dynamic heat problems for a porous medium modelled as an idealized geometry consisting of a periodic array of cylinders. Different cross-section shapes of the cylinders (circular, ellipsoidal and square cross-section shapes) and a wide range of porosity values are considered. The influence of the microscopic features of the porous media on dynamic permeability and dynamic compressibility is also studied.
Quasicollinear acoustooptic tunable filters based on KDP single crystal
Authors: Molchanov Vladimir , Chizhikov Sergei , Makarov Oleg
Published: May 2008

The paper is devoted to the theoretical and experimental investigation of acoustooptical tunable filters, based on quasicollinear geometry of light-sound interaction in KDP single crystal. This geometry uses the effect of acoustic anisotropy in KDP, as well as peculiarities of acoustic wave reflections from the free boundary of KDP crystal. The mathematical approach for determination of optical and consructional characteristics of the filters is elaborated. Different types of quasicollinear filters are considered. The filters are intended for UV-VIS regions of optical radiation. The experimental acoustooptical filter was designed and investigated. Typical tunable spectral band is 220-500 nm, the spectral resolution doesn't exceed 0.1 nm in UV region of spectra. The experimental data are in a good agreement with the predicted one. This research is supported by RFBR grants # 07-02-12238 and # 07-02-01195.
Bragg light diffraction in nontransparent crystals
Authors: Akhmedzhanov Farkhad
Published: May 2008

As is well known, in absolutely transparent crystals an acoustooptical interaction is lacking. In this connection's acoustooptical investigations are presented greatest interest in optical range, in which the crystal is not transparent. In order to carry out similar experiments, it is necessary to use the crystal with a small light absorption coefficient at applied wavelength. The main problem is selection of an appropriate buffer crystal that the light beam can penetrate into sample by Bragg angle at required frequency. At present work the acoustooptical properties of Si crystal were investigated at light wavelength 632.8 nm. Dy2S3 crystals were used as a buffer sample. It was detected the diffracted light intensity is much more powerful in comparison with that for LiNbO3 crystals. Acoustooptical efficiency M2 (it is defined the acoustic-optical quality of material) has been calculated from the values of optic coefficients and elastic constants for appropriate directions of sound and light. The results of executed investigations have shown the possibility of determination of acoustooptical properties of nontransparent crystals by Bragg diffraction method. At that rate, the very high intensity of diffracted light can be obtained in comparison with that in transparent crystals.
Sources and potential influences of uncertainty in ground impedance measurements and estimations
Authors: Taherzadeh Shahram , Attenborough Keith
Published: May 2008

Knowledge of acoustic impedance of ground surface is essential for determining noise levels outdoors. At distances up to a few hundred metres from the source ground effect may be the dominant factor. The short-range measurement of sound level spectra from an omni-directional source has been used as a standard method to deduce the acoustic impedance spectrum of ground surfaces (e.g. ANSI S1.18, 1999). However, there remain a number of uncertainties in such measurement methods. For example, at low frequencies the difficulties in fitting theoretical or phenomenological models to short range data may result is a large uncertainty in predictions of sound levels at larger distances. Another source of uncertainty is the variability of the acoustic impedance of apparently uniform ground. Another potential influence on predictions of long term equivalent noise levels is seasonal variation. This paper discusses the extent and potential influences of such uncertainties in measured and deduced ground impedance spectra.
Long range propagation of high speed train noise: Sound level variations before and after the pass-bys
Authors: Cotte Benjamin , Blanc-Benon Philippe , Poisson Franck , Cremezi-Charlet Cora
Published: May 2008

It has been observed relatively frequently that high speed train (TGV) noise could be heard tens of seconds before or after the actual train pass-bys. This study is aimed at characterizing this phenomenon and the conditions in which it occurs, both experimentally and numerically. Acoustic measurements of TGV pass-bys have been performed under controlled conditions. A relatively strong wind was blowing from the South during the experiment. The measurements show that the TGV noise can be heard before the pass-bys when the TGV was coming from the South (same wind and train directions), and after the pass-bys when the TGV was coming from the North (opposite wind and train directions). This noise is relatively low in frequency (around 400 Hz), and corresponds to propagation distances that can exceed 1 km. Levels associated with this phenomenon can vary significantly over short time intervals (5-10 minutes), which raises the issue of the representativeness of TGV measurements at long ranges. It will be shown using numerical prediction methods (parabolic equation in the frequency domain, linearized Euler equations in the time domain) that these acoustic variations are mostly due to variations in the meteorological conditions between the pass-bys.
Road noise: characterization and estimation of uncertainty due to meteorological effects
Authors: Ecotiere David
Published: May 2008

Meteorological effects can lead to important temporal fluctuations of the sound level in outdoor sound propagation. These fluctuations lead to sound level uncertainties that are rarely estimated. A method based on the coupling of a model of sound propagation and a temporal micrometeorological model is used to quantify sound level fluctuations only due to meteorological fluctuations, over a very long period (typ. 10-30 years). Some statistical analysis are presented: diary or seasonal fluctuations, influence of the duration of observation on the accuracy of the estimation of a LAeq. A semi-analytical method is also proposed for characterizing the uncertainty of the sound level of a distribution of punctual sources. An application to a road noise source is presented.
An experimental evaluation of a new approach to aircraft noise modelling
Authors: De Roo Foort , Salomons Erik
Published: May 2008

Common engineering models for aircraft noise, such as INM, yield noise levels by interpolation of Noise Power Distance (NPD) tables. In the European project Imagine (2004 2006), a different approach was proposed: the source is characterized by an emission spectrum and the received noise spectrum is calculated by subtracting the propagation attenuation spectrum from this emission spectrum. This is the usual approach for noise mapping of most noise sources. The aircraft emission spectrum is a function of (downward) emission direction, so each aircraft is represented by a hemisphere of emission spectra. This has been described by Butikofer in Acta Acustica 93 (2007). As hemisphere emission data are not yet available for all aircraft types, a 'reverse engineering' scheme was developed within Imagine to derive first order estimates of hemispheres from NPD tables. To gain experience with this approach, we have performed an experiment near Amsterdam airport. Various types of data were collected for a set of aircraft departures, including noise data at eleven positions and flight data. The Imagine approach was used to calculate noise contours, and noise spectra at the eleven positions. The differences between measured and calculated spectra may be used as a basis for improving the first order estimates of the hemispheres.
Acoustical waves propagation in rough walls street
Authors: Lihoreau Bertrand , Félix Simon , Depollier Claude
Published: May 2008

We present a method for the numerical calculation of a sound wave propagating in a two dimensional rough-sided street. Is this situation, the wave is subject to multiple scattering at the two boundaries. The propagation is governed by a parabolic equation. We show that the amplitude of a pulse may be expressed as the fractional Fourier transform of the incident pulse, and that the order of the transformation is related to the distance between the source and the point of observation. Numerical simulations are proposed as illustration of this model and are compared to experimental results.
Acoustic phenomena in porous media studied by transient grating spectroscopy: a critical test of the Biot theory
Authors: Cucini Riccardo , Taschin Andrea , Bartolini Paolo , Torre Renato
Published: May 2008

The propagation of sound in a porous solid filled by a liquid can be described by a phenomenological model introduced by M. A. Biot, that is still extensively used to predict the essential acoustic properties of a wide variety of porous media. Nevertheless testing of the Biot theory at ultra/hypersonic frequencies and in porous media with nanometric scale heterogeneities remains an open issue. We studied the propagation of acoustic waves in two liquid-filled porous glasses by heterodyne detected transient grating experiments [1]. A test of the Biot theory is presented under two new regimes, namely, for a new frequency range up to 1.3 GHz and for porous media with nanometric scale heterogeneities [2]. We show that the Biot theory describes the sound velocity data correctly, but does not account for the acoustic attenuation. We suggest that the acoustic damping is mainly due to the dissipation mechanisms intrinsic of the matrix and the liquid which are not accounted for in the theory. [1] Time-resolved spectroscopy of complex liquids, edited by Torre R. (Springer, New York) 2008. [2] A. Taschin, R. Cucini, P. Bartolini, R. Torre, Europhys. Lett. In press.
Zero-group velocity modes and local vibrations of an elastic plate
Authors: Prada Claire , Clorennec Dominique , Royer Daniel
Published: May 2008

Elastic plates or cylinders can support guided modes with zero group velocity (ZGV) at a nonzero value of the wave number. The conditions required for the existence of ZGV Lamb modes in isotropic plates are discussed. It is shown that these modes appear in a range of Poisson's ratio over the value for which the cut-off frequency curves of modes belonging to the same family intercept, i.e for a bulk wave velocity ratio equal to a rational number. An interpretation of this phenomenon in terms of a strong repulsion between a pair of modes having a different parity in the vicinity of the cutoff frequencies is given. Using laser-based ultrasonic techniques, we experimentally investigate some properties of these ZGV Lamb modes: resonance, backward wave propagation, interference between backward and forward waves. Experiments performed with materials of various Poisson's ratio demonstrate that the resonance spectrum of an unloaded elastic plate, locally excited by a laser pulse, is dominated by the ZGV Lamb modes. From these local resonance frequencies, thickness variations can be measured accurately and material properties like the Poisson's ratio, bulk acoustic wave velocities or material attenuation can be determined without any mechanical contact.
Simulation of wave field synthesis
Authors: Völk Florian , Konradl Josef , Fastl Hugo
Published: May 2008

Wave field synthesis utilizes a large number of loudspeakers to generate a desired wave field. It therefore is necessary to drive each speaker with an independent signal, which requires as many amplifier and soundcard channels as there are loudspeakers. These enormeous hardware costs make research and development very expensive and time consuming. Additionally, different rooms influence the wave field synthesis arrays in different ways. For this reason a simulation technique is of advantage which permits the evaluation of the perceived properties of arbitrary wave field synthesis configurations without the need to physically construct them. This paper proposes a simulation system capable to simulate wave field synthesis systems in different rooms based on physical measurements of one loudspeaker in each room. The techniques used are presented, and possiblities as well as limits of the system are discussed.
Auditory memory and evaluation of environmental sounds
Authors: Kuwano Sonoko , Namba Seiichiro , Kato Tohru
Published: May 2008

A series of experiments were conducted concerning the memory of environmental sounds. Twelve kinds of sound were presented with soft background noise of about 6 min to participants. They were asked to recall or recognize the sound sources and to judge the loudness of the recalled or recognized sounds some period after they listened to the sounds. The recalled or recognized loudness was examined in relation to the length of the period between the presentation of sounds and the judgment of loudness, the method to measure the memory, LAeq of each sound source, etc. The results suggest that it is possible to judge the loudness of the memorized sounds and that the judgments seems reliable.
Automotive tire/road sound quality
Authors: Cerrato Jay Gabriella , Freeman Todd , Raglin Chris , Carson Timothy
Published: May 2008

Tire/road noise and sound quality are increasingly important factors for customer satisfaction. As vehicle interior sound levels decrease, the noise from tires and their interaction with the road become more noticeable. Both tire and vehicle manufacturers need to assess as early as possible the impact of any tire-vehicle combination on perceived interior sound quality. In this paper, we describe two projects in which psychoacoustics concepts were applied to help, on one hand, tire manufacturers to screen for designs likely to generate poor sound quality in vehicle, and, on the other hand, vehicle manufacturers to measure the impact of road noise and interior acoustic treatment on speech transmission in the cabin. In both projects, the activities were driven by the understanding of the psychoacoustic features of tire/road noise and by the need to improve customer satisfaction.
An efficient masking model for audio coding exploiting spectro-temporal masking
Authors: Van De Par Steven , Koppens Jeroen , Kohlrausch Armin , Oomen Werner
Published: May 2008

Perceptual audio coding achieves part of its coding efficiency by spectrally shaping the quantization noise such that it is masked by the audio signal to be encoded. In order to determine how much quantization noise is allowed within each frequency band and time interval a masking model is used to predict a masking curve specifying the maximally allowed quantization noise level within each frequency band. In most audio coders only spectral masking properties of the audio signal are used. The model by Dau et al. [J. Acoust. Soc. Am. 99, Vol. 3615, 1996] provides an interesting approach to also model temporal masking. Since this model operates as an artificial observer it only predicts whether the quantization noise is audible or not in the presence of the audio signal. In order to determine the most efficient quantization noise shape, the encoder needs to iteratively adapt the noise shape and evaluate each option with the model. This implies a highly computational complex encoding algorithm. In this contribution we will present an efficient masking model based on the Dau et al. model that only requires a single evaluation of the input signal to determine the maximally allowed noise level within each frequency band.
Optimization of a dual recognition tasks for speech quality assessment
Authors: Durin Virginie , Gros Laetitia
Published: May 2008

This paper deals with perceptive test methodologies to assess speech quality of telecommunication systems. Faced with drawbacks of typical methodologies recommended by ITU-T, a new way to assess speech quality is investigated. The new approach requires collecting reaction times and performances when subjects are achieving tasks involving degraded speech signals; it is shown that reactions times lengthen and performances decrease in a specific task when quality is impaired. The proposed task is a dual task with a digit recognition memory task and a letter recognition task. Three different quality levels are applied to audio signals describing digits and letters. Different experimental designs are examined to reinforce the effect of speech quality on performances and reaction times. The results show significant differences of performances and reaction times between the three quality levels, depending on the experimental design.
Methodological aspects in the determination of the auditory filters and critical band at low and mid-frequencies
Authors: Jurado Carlos A. , Mo/ller Henrik , Pedersen Christian Sejer
Published: May 2008

In order to evaluate loudness or audibility of complex sounds, knowledge of the auditory filter characteristics is necessary. At low frequencies, where both the threshold of hearing and dynamic range become considerably frequency dependent, care must be taken to account for this both in the psycho-acoustical model and the methodological approach. To account for variation in hearing sensitivity at low frequencies, equal loudness contours have been used to weight the stimuli accordingly. At mid and high frequencies, threshold of hearing curves have been used. These stimuli weightings can be applied before or after the experiment, normally being applied afterwards. Due to the non-linear characteristics of the cochlear amplifier, it is arguable whether post-experimental weighting is a proper approach, or whether at low frequencies there will be any difference between pre or post stimuli weighting. Listening experiments are then to be performed to test possible differences in pre or post filtering the stimuli. The most appropriate approach will then be discussed. Measurements will be done at low and mid frequencies. To obtain accurate auditory filter estimates, individual ELC or threshold curves will be determined. Methods such as the notched-noise method and the classical band-widening approach will be tested with these conditions.
Relation between the overall unpleasantness of a long duration sound and the one of its event6: application to a delivery truck
Authors: Geissner Emilie , Parizet Etienne
Published: May 2008

The goal of this study was to investigate the link between the unpleasantness assessment of an unstationary long duration sound composed of several distinct sound events and the corresponding judgments of each of those events. For that purpose, a sound sequence of a delivery truck was evaluated by 16 listeners during a test in laboratory: first, subjects had to continuously quantify the perceived unpleasantness of the sequence by moving a sliding cursor along a five levels graduated scale and then give a global rating by using the same scale. In a second step, listeners had to express their overall judgment of unpleasantness for eight samples of the delivery sequence. As previously shown for loudness by Kuwano and Namba (1985), the global rating of the unpleasantness of long sound could not be estimated by the arithmetic mean of the continuous assessment. It also appeared that the overall judgment corresponds to the arithmetic mean on the local values of unpleasantness of each main sound event. This last result was similar to the conclusions of Hellbrück et al. (2001) for the loudness scaling of traffic noise.
Signal processing in hearing aids: results of the HEARCOM project
Authors: Wouters Jan , Luts Heleen , Eneman Koen , Spriet Ann , Moonen Marc , Büchler Michael , Dillier Norbert , Dreschler Wouter A. , Froehlich Matthias , Grimm Giso , Hohmann Volker , Houben Rolph , Leijon Arne , Lombard Anthony , Mauler Dirk , Puder Henning , Schulte Michael , Vormann M
Published: May 2008

Digital hearing aids of today allow the application of advanced signal processing strategies. In recent years a number of promising signal processing approaches have been designed and developed. However, most of these different evolutions have been evaluated only in a limited way. Within the framework of the HEARCOM EU-research project a number of signal enhancement techniques have been further developed and evaluated based on a representative set of real-life recordings and physical performance measures. Different auditory profiles, representing common categories of hearing aid users, have been taken into account. A selection of 5 of these signal enhancement techniques (single-channel noise suppression, blind source separation, dereverberation, multi-microphone adaptive processing, feedback reduction) has been implemented on a single common hard- and software test platform, the Master Hearing Aid (MHA). These signal processing strategies have been evaluated perceptually based on speech reception thresholds, listening effort and preference rating, at 5 different test-sites for a number of speech-and-noise listening scenarios. Fifty normal hearing subjects and 100 hearing aid users according to 2 auditory profiles, took part in this study.
Binaural function and its benefits for wearers of hearing aids
Authors: Kalluri Sridhar , Edwards Brent
Published: May 2008

Hearing-aid design has been predicated traditionally on improving the reception of speech in background noise, a goal that has, at least in part, been successfully attained. Despite the advances, hearing-aid wearers continue to have difficulty in complex acoustic environments and in auditory tasks where normal-hearing listeners benefit greatly from binaural hearing. In order to improve hearing-aid wearers' performance in such challenging conditions, recent research has begun examining the effects of hearing aids on binaural perception. Interest in the topic is heightened by the rapidly approaching prospect of bilateral hearing aids that communicate wirelessly and thereby allow implementation of more complex signal-processing algorithms than currently possible. This talk will review binaural function and its benefits, with particular emphasis on the aspects that hearing aids can affect. The talk will also speculate on which hearing-aid algorithms can affect binaural perception.
The effect of binaural processing techniques on speech quality ratings of assistive listening devices in different room acoustics conditions
Authors: Odelius Johan , Johansson Örjan
Published: May 2008

External microphone systems, referred to as assistive listening devices (ALD), are used in classrooms for hearing impaired students. The objective is to investigate the effect of binaural processing techniques in different room acoustic conditions. A listening experiment was conducted with 10 normal hearing adults. Response variables were judgements of clarity, pleasantness, listening effort and overall speech quality. Design variables were binaural processing, room acoustics and ALD bandwidth. Stimuli were generated using the room acoustic modelling software CATT Acoustic. Three speech sources, two male voices and one female voice, were placed at a table in the centre of a room and one Brown noise source was placed in one corner of the room. Microphones were placed 0.5 m in front of each speech source. Target source was a random choice of one of the two male voices. The binaural processing was utilized by a simple HRTF filtering. Depending on the angle to the source from a fictitious listening position at the table, corresponding interaural time difference (ITD) and the interaural level difference (ILD) was applied to the signal. Stimuli were presented by loudspeakers using cross-talk cancellation. The hypothesis is that binaural processing will give a significant improvement in speech quality.
Acoustic and vibration measurements of NASA spacesuits
Authors: Begault Durand R. , Hieronymus James L. , Adelstein Bernard D.
Published: May 2008

Research was conducted to examine interactions between acoustic signals and mechanical factors relevant to the design of improved auditory displays and noise mitigation for future NASA Spacesuits. Data were collected at NASA Johnson Space Center for the current Mark III advanced prototype surface suit during walking, walking with arm motion, and while seated. Measurements were made using multiple microphones (both head mounted and helmet mounted) and a tri-axial accelerometer to evaluate the effects of suit-borne vibration on overall background noise. Footfall impacts were found to create temporary depolarization of condenser microphone signals, and microphone positioning had a strong effect on signal-noise ratio, partially due to the effect of the helmet enclosure. The results indicate noise mitigation and signal conditioning strategies for improving lunar suit audio voice communications under extra-vehicular (EVA) conditions. Funded by a directed research program of NASA's Space Human Factors Engineering project and by NASA-JSC's Constellation EVA system audio group.
Amodal specification of talker-specific motor behavior
Authors: Rosenblum Lawrence D.
Published: May 2008

There is substantial evidence that the speech perception function incorporates information for articulatory motor behavior. Research over the last 15 years has shown that speech perception also uses information for talker-specific motor behavior. Interestingly, this research reveals that talker information can facilitate speech perception whether it is apprehended through auditory or visual speech (lipread) means. The multimodal nature of these effects could mean that the talker-specific properties used by the system are amodal and motoric-or gestural-in nature. Evidence for this proposition-that talker-specific facilitation of speech is based on amodal specification of gestural style-will be discussed. This evidence includes findings that isolated talker-specific phonetic information, available both optically and acoustically, can be informative about talker identity to the degree that it supports cross-modal talker matching. Other evidence shows that the talker familiarity gained through one modality can facilitate perception of speech in the other. Finally, recent evidence reveals that speech perceivers will align to (inadvertently imitate) talker-specific properties of utterances they are asked to shadow, whether that speech is presented auditorily or visually. These results suggest that some of the 'motor knowledge' bearing on speech perception takes the form of talker-specific gestural properties, amodally specified.
Time reversal and subwalength focal spot
Authors: De Rosny Julien , Tourin Arnaud , Lerosey Geoffroy , Fink Mathias
Published: May 2008

When a wave is time-reversed inside a homogeneous medium, the focal spot width at best equals half a wavelength. This limit comes from the loss of evanescent wave during propagation. An analysis of the time reversed field in terms of the Green's function formalism shows that in order to get a finer spot, not only the field has to be time reversed but also the initial source. In such a case, an acoustic sink is obtained. Experimental results are presented. Then we show two methods to obtain subwavelength focal spot without time-reversed source. The first method consists of setting the time reversal mirror in the near field of the initial source. Despite the evanescent wave transmission, we will see that subwavelength focusing is only observed for a special time-reversal mirror. The second method consists of surrounding the initial source by many scatterers. In such a case, the evanescent waves emitted by the initial source are converted into propagating ones. During the time reversal step, back-conversion occurs that leads to a sub wavelength focal spot. Thanks to this principle, a focal spot of a thirtieth of a wavelength has been reported in the case an electromagnetic experiment.
Seafloor studies at NURC/SACLANTCEN: The first 50 years (1959-2008)
Authors: Richardson Michael
Published: May 2008

Characterization of the seafloor has always been one of the central research themes at NURC/SACLANTCEN. These studies, reviewed in this presentation, generally supported acoustic measurement and modeling programs. Motivation for bottom-interacting acoustic research began with the deep-water ASW programs of the 1960s and 1970s (long-range propagation, reflection, and bottom loss measurements) and slowly evolved into support for high-frequency, shallow-water MCM programs of the 1990s and 2000s (acoustic propagation within sediments, penetration into and scattering from the sediment surface). Seafloor characterization has included scales appropriate for plate tectonics to sub-mm scale sediment microstructure used to statistically characterize sediment heterogeneity for high-frequency acoustic studies. Although collection and analysis of sediment cores has been the dominate methods of seafloor characterization, direct in situ measurements and remote acoustic characterization has often been used. Seafloor studies were first rate, cutting edge research as demonstrated by quality and quantity of peer-reviewed publications by NURC/SACLANTCEN scientists and their post-SACLANTCEN research careers. The excellent engineering department made possible the development of unique acoustic and seafloor sampling equipment. Ship support for seafloor studies has always been a NURC/SACLANTCEN advantage that has attracted many scientists to multi-national, multi-institutional experiments and symposia.
NURC/SACLANTCEN contributions to sonar signal processing and ASW systems research
Authors: Abraham Douglas
Published: May 2008

The NATO Undersea Research Centre (NURC) was established in 1959 as the SACLANT ASW Research Centre and tasked with providing scientific research and technical analysis in the area of antisubmarine warfare (ASW) to NATO nations. This presentation will review NURC's contributions to sonar acoustic research in the areas of sonar signal processing and ASW systems. These contributions span at-sea testing and experimentation of novel sonar system concepts to algorithm development and theoretical advances in sonar signal processing. The diversity of expertise across fields such as oceanography, acoustics, signal processing, systems, and operations research brought by international scientists into the cauldron of a small, focused research centre with world-class technicians, engineers, and at-sea capabilities produced innovative, interdisciplinary research. [Supported by the Office of Naval Research Code 321US under contract number N0001407C0092]
NURC/SACLANTCEN milestone experiments toward solving inverse problems in ocean acoustics
Authors: Hermand Jean-Pierre
Published: May 2008

This paper reviews milestone experiments conducted by Saclant Undersea Research Centre to support the development and validation of techniques for obtaining and taking into account environmental information in sonar. The experiments brought together underwater acousticians, geophysicists and oceanographers with the aim to collect comprehensive acoustic and environmental ground-truth data. Environmental-adaptive signal processing was first demonstrated in a deep water area (WESTSARDINIA'89&90). From ducted propagation measurements, a model-based matched filter (MBMF) receiver that fully incorporates the physics of wave propagation determined a source range, depth and Doppler. For environmental inversion the broadband extension of matched-field processing was investigated in a shallow water area south of Elba island (YELLOWSHARK'94&95). Geoacoustic properties of the sea bottom were determined by finding the best fit between predicted and observed sound fields at multiple frequencies using genetic search algorithms. The same inversion results were obtained by MBMF processing of broadband linearly-frequency-modulated signals enabling the use of an array of a few hydrophones instead of a dense and large vertical array. This motivated the development of drifting acoustic buoys which were tested successfully over the southern continental shelf off Marettimo island, Sicily (ENVERSE'97&98). A recent experiment demonstrated an integrated concept of Rapid Environmental Assessment (MREA/BP'07) using sparse arrays of hydrophones and pressure/temperature sensors, hand-deployed from small vessels.
Diagnosis of an historical performance hall: case study
Authors: Serra Maud
Published: May 2008

The Opera of Vichy is an historical Italian style performance hall. Initially solely devoted to opera performance, the economical trends have pushed towards concert and theatre. A first major refurbishment was performed in the 1990s and prior to that a diagnosis of that hall was performed in order to characterize the acoustics of the facility prior to actual work being carried out. While the historical preservation constraints did not allow for much acoustical work to be performed, the hall proved to be quite decent. However, in order to improve the intelligibility for theatre purposes, a new diagnosis was recently carried out so as to support the relevant computer simulations. After a brief reminder of the historical background of the project, this paper submits the diagnosis procedure that was followed, as well as its main conclusions regarding the fitness of the hall for the various performances. It turns out that such a diagnosis can be a convincing tool in order to help both the design team and the end user understand the implications - and the limitations too!- of the existing facility and its possible developments.
Data Handling of a Perennial Acoustic Observatory in the Antarctic Ocean
Authors: Kindermann Lars , Klinck Holger , Van Opzeeland Ilse Catharina
Published: May 2008

In December 2005, 4 broadband hydrophones were deployed through boreholes under the 100m thick floating ice shelf near Atka Bay, Antarctica. Since then, more than 10,000 hours of underwater sounds have been recorded, containing marine mammal vocalizations and the unique background sounds generated by ice and the occasional ship. These records from this pristine region are analyzed in terms of the local noise budget, the behaviour of marine mammals and anthropogenic impacts. The observatory is energetically self-sufficient and connected by a 15km WLAN link to the year-round manned German Neumayer Base, where a leased satellite line allows live streaming of highly compressed audio to http://icecast.awi.de. While the recording device is capable of four channels / 192kHz / 24Bit, this cannot be transferred continuously through the WLAN and satellite link, so a multi-stage automatic buffering and selection scheme is implemented to allow for both, continuous coverage and high quality recordings of selected events. About two terabytes per year are automatically streamed into the petabyte data storage of the World Data Centre for Marine Environmental Data, hosted by AWI, where they are analysed and prepared for publishing under an open access license.
Single parameter description of seafloors for shallow oceans
Authors: Jones Adrian D. , Day Graham J. , Clarke Paul A.
Published: May 2008

For a shallow ocean, sound transmission beyond short range is dominated by seafloor interactions at small grazing angles, for which the loss in dB on each bottom reflection may be approximated by a function F dB/radian which is linear with grazing angle. Acoustic inversion techniques have been shown to be able to obtain the value of F for a particular frequency. The suitability of this single parameter F as a seafloor descriptor has now been studied for an extensive range of seafloor types. It is shown that the phase-incoherent transmission loss (TL) obtained using the parameter F is not greatly different to TL predicted using complete knowledge of a particular seafloor, for a shallow ocean. Further, if the phase angle for a seafloor reflection is linked to the parameter F via a simple approximation, the phase-coherent properties of the shallow water interference field may be estimated to an accuracy which is surprising. This paper reviews the relevant theory and presents comparisons between TL predicted using full geoacoustic parameters versus TL based on the single parameter, for both uniform half-space and layered seafloor types.
A mixin algorithm for geoacoustic inversion
Authors: Dong Hefeng , Jenssen Arne Johannes
Published: May 2008

Shear wave velocities in the sediment can be inverted by using the dispersion curves of interface wave. It can be done by use of an algorithm based on singular value decomposition (SVD). This method can only invert the shear wave velocities and requires knowledge of the thicknesses and densities of the sediment layers. This paper presents a new algorithm for inversion of geoacoustic parameters based on dispersion curves that we have coined "mixin inversion". Mixin inversion combines SVD and global search using genetic algorithm (GA). The GA searches the depths and densities by doing a shear wave velocity inversion with SVD for each of its parameter values. This algorithm can be applied on cases where the depths, densities and shear wave velocities of the sediments are unknown. The advantage is that it is faster than pure GA since the search space is much smaller and it can be applied on cases where pure SVD inversion fails because necessary information about depths and densities is not known.
Improvement of the GMM-AR classification of multiframe contrast ultrasound images using gaussian filter
Authors: Ghazal Bilal , Khachab Maha , Friboulet Denis , Mokbel Chafic , Cachard Christian
Published: May 2008

Despite the use of contrast agents that enhance the visualization of vascular zones, the backscattered signals from the contrast agent and tissue are still close which prevents the direct wide ultrasonic use in diagnosis. Thus, it was necessary to implement image-processing techniques that enhance the contrast echo and have the capability of classification. We have applied a new approach based on the autoregressive model where an image of prediction errors is calculated in the first phase. Then, a Gaussian filter is applied in order to model well afterward both agent and tissue behaviors by a Gaussian mixture model. The Agent to Tissue Ratio (ATR)factor and Fisher criterion are adopted to compare the performance of this method with existing techniques as the harmonic and B mode techniques. The experiments conducted have shown the advantages of our proposed approach where an increasing of ATR and Fisher are recorded. In fact, our ATR attains 19.20 dB which represents a good improvement in comparison with B mode (9.50 dB) and Harmonic technique (12.13 dB). Whereas Fisher, the parameter of classification feasibility, it reaches 2.01 which matches an excellent amelioration with respect the mentioning techniques with 0.97 and 1.00 respectively.