bluuebunny/crossref_metadata_2025 huggingface dataset:
The development of a bespoke gunfire noise model for a military training area and the vibration impacts through the air on ancient structures
Authors: Parry Graham
Published: May 2008

This paper describes the development of a bespoke weapons system noise model known as the gunfire noise analysis tool (GNAT). The requirements for such a model came out of an expansion of military training within a National Park and the need to demonstrate that noise impacts could be modeled with reasonable accuracy out to distances of 10 kms and without the need for specialist acousticians or meteorologists to run the model. Additionally, the requirement was to ensure that noise modeling could be carried out within a matter of minutes thus allowing military training decisions to be made while protecting sensitive receptor locations from very high noise levels. The model utilised best practice and acoustic theory available at the time within the specific requirements of noise modeling outlined above. The model was validated against a number of noise measurements exercises carried out using controlled military noise events and for a live military exercise.
Transducers for acoustical impulse measurements
Authors: Rasmussen Per
Published: May 2008

The measurement of impulsive noise signals as for example from gunshots or airbag deployments requires special considerations when selecting transducer. The high frequency content in short impulses requires high bandwidth to correctly capture high rise times and small dimensions of the transducer to avoid diffraction. For high level impulses with very rapid rise time, the wide frequency range requires the use of preamplifiers with high slew rate capabilities and the capacitance and length of cables must be considered carefully. Slew rate limitations and bandwidth limitations can drastically change the peak value of an impulse. It is thus necessary to consider the whole measurement chain from transducer to AD-converter to ensure the correct measurement of the impulse.
Large weapon source emission data protocols and results
Authors: James Michael , Downing Micah , Larry Pater
Published: May 2008

The U.S. Army needs detailed information about the blast pressure field created by large weapons to avoid negative impacts on testing and training mission capabilities due to noise. The noise software tools BNOISE2™ and RMTK Noise Tool, which the Department of Defense (DoD) uses to predict and assess impacts of large weapon noise, require accurate acoustic source emission models. A free-field representation of the sound source acoustical emission, containing no waveform signal perturbations due to the ground, other reflecting surfaces, ballistic waves, or propagation anomalies, is required. The measurement protocols have been developed to collect the free-field source emission data. These protocols are described along with acoustical data and emission source results for the 120 mm M-1 tank gun, the 105 mm Stryker gun, and various weights of C-4 explosives. In addition, the measured acoustic data are compared with an idealized Friedlander curve. The overall results demonstrate that the protocols do provide sufficient free-field blast waveforms.
Monitoring of noise reduction from traffic speed control
Authors: Jabben J. , Potma C.
Published: May 2008

In November 2005, at the Hague, Amsterdam, Rotterdam and Utrecht, a 80 km/u speed limit was introduced on sections of motorways in the Netherlands. The aim was to evaluate the effects on noise, air quality and the circulation of the traffic. RIVM investigated the effects of noise emission by direct measurement at the sections with speed limit. This paper gives the results from continuous monitoring of noise levels that was started at July 2005 and continued up to November 2006. In the presentation the average measured effects on the equivalent noise emissions at the different sites will be given. Also the effects of traffic speed reduction on dwellings in the neighborhood of the motorways were evaluated using noise maps. Furthermore, apart from the average equivalent noise levels, the statistical noise indicators L5, L10, L70, and L95 were continuously monitored. It was found that speed reduction induces more reduction on maximum noise levels than on the average (equivalent) noise levels, probably due to a more steady and even distribution of traffic speeds.
Automatic classification of traffic noise
Authors: Sobreira-Seoane Manuel A. , Rodríguez Molares Alfonso , Alba Castro José Luis
Published: May 2008

When modeling a city or a secondary road to calculate a noise map, the information about the number of heavy/light vehicles and the average speed it is not always available. In this paper, a first approach to get an automatic classification of vehicles is presented. The system is based on the classification of the audio signal that a noise source produces. Some basic classifiers have been tested (k-nearest neighbours, FLD (Fischer linear discriminator) and principal components. As first approach, the aim of the job was to determine if the different classes (trucks, cars, and motorbikes) could be separable using different time and frequency characteristics: zero crossing ratios, spectral centroids, spectral rolloff, subband energies and mel frequency cepstral coefficients. The results shows that for some of the characteristics tested, the signals are separable, so a continuous traffic noise signal could be processed to get the information of the number of heavy trucks, cars, and motorbikes that passed by during the recording time. Information of a stereo recording could be used to get information of the direction of the vehicle. At this moment, combining three characteristics and FLD, errors bellow 9% can be reported.
Numerical simulation of aerodynamical noise generated by a cylindrical cavity
Authors: Mincu Daniel-Ciprian , Redonnet Stephane , Mary Ivan , Larcheveque Lionel , Manoha Eric
Published: May 2008

Cylindrical cavities are mounted at some positions on fuselage and wings of commercial transport aircraft for various service functions. Such cavities were identified as potential airframe noise sources generating high intensity whistles at frequencies situated in the audible range of 0.5-0.8 kHz. The present paper focuses on the numerical simulation of the far field noise generated by the unsteady flow passing over a cylindrical cavity with an aspect ratio (diameter/height) equal to unity, using a numerical methodology combining a LES and a Kirchhoff integration method. The LES computation was done using ONERA's cell-center/finite-volume/CFD code named FLU3M. A laminar boundary layer profile was applied upstream the computational domain, without forcing any turbulence. The LES results were coupled with a 3D Kirchhoff method in the frequency domain. The computed far field noise was compared to dedicated experimental data, showing very good agreement, especially regarding the emission frequency. The final paper will present in detail the involved numerical methods, the computational procedure, and several comparisons to experimental data. This study was completed in the framework of the AEROCAV (AEROacoustique d'une CAVité cylindrique) project funded by the FRAE (Fondation Recherche Aéronautique et Espace).
Efficient method for harmonics estimation of car engine sounds: application to high quality real-time synthesis
Authors: Molla Stephane , Jaillet Florent , Gauduin Benoı̂t
Published: May 2008

Additive synthesis is the most popular method for the resynthesis of sounds containing slowly evolving harmonics or partials, such as car engine noise and more generally rotating machines sounds. The most important step lies in the estimation of the amplitude and frequency of each sinusoidal component. It appears that insufficiently precise estimation often leads to unsatisfactory results in terms of sound fidelity. A method providing the time and frequency evolution of the amplitude of the harmonics of a recorded sound is presented. This technique is based on a joint time and frequency chaining of amplitude's extrema of amplitudes coming from a short-time Fourier transform, using forward and backward estimation. The proposed method is compared to a rough estimation, and to an estimation based on measured tachometric data, all carried out over the same car engine sound. This estimation method is implemented into the LEA software, which thus allows fast and precise computations of the parameters. Moreover, it also helps in estimating the frequency content of the “background” noise, which depends on the speed, allowing the extraction of the partials from the original sound in an easy and efficient way. Once these characteristics are found, a high quality real-time synthesis is possible.
A simple acoustic model to characterize the internal sound field in centrifugal pumps originated by blade-tongue interaction
Authors: Parrondo Jorge , Perez Javier , Barrio Raul
Published: May 2008

Conventional centrifugal pumps with volute casing generate fluid-dynamic noise particularly at the so-called blade-passing frequency, due to the interaction of the flow exiting the pump impeller with the volute tongue. The amplitude of the sound generated is very dependent on the pump operating point. Following previous studies by the authors, a methodology has been applied to quantify the generation of tonal noise for a given centrifugal pump, previously tested in laboratory. The procedure is based on a simple acoustic model for the pump, in which one or several ideal point sources are located at some arbitrary position in the volute. These ideal sources are assumed to radiate plane sound waves along the volute, which was considered to be composed by a succession of slices, each of them equivalent to a linear three-port acoustic system with sound transmission and reflexion coefficients according to the corresponding port areas. A series of tests was conducted to check the assumptions of the acoustic model, by applying external acoustic loads onto the pump outlet duct and measuring the noise reflected. The resulting reflection coefficient was in good agreement with the predictions of the acoustic model.
Performance evaluation method for high noise environment intercom headsets
Authors: Potirakis Stelios M. , Moisiadis Yiannis , Varagis Antonis
Published: May 2008

Intercoms' use in high noise environments (HNE) is typical since direct speech communication of individuals is difficult or even impossible. The headset selection for such an application is crucial since it serves both for noise attenuation and voice reproduction. It has been recently acknowledged in telecommunications (ITU-T/P.380) that headset electroacoustic measurements should be performed on head and torso simulator (HATS). However, in military applications where headsets are mainly used in HNE there is not a standard performance evaluation method but only for the earphone elements (MIL-PRF-25670B), thus excluding the acoustics of the earcup cavity, absorbing materials and face fitting quality. It is well known that the reproduced speech level should be of about 10 dB above noise level to achieve good intelligibility, so both sensitivity and noise reduction capability should be measured on a HATS to evaluate such a headset. In this work, a systematic methodology for measurement and performance evaluation of HNE headsets is proposed based on HATS. Critical aspects that may affect the test procedure, such as HATS response and the right headset placement are examined. Finally, a series of measurements prove the value of the proposed method. Large differences are revealed even for headsets following the same standard.
Monitoring hurricanes using infrasound
Authors: Talmadge Carrick L. , Hetzer Claus , Bass Henry E.
Published: May 2008

In spite of recent technological advances, forecasting the intensity of a hurricane remains a challenging problem. Knowledge of the location and the strength of the storm at the moment where it makes landfall is critical for civil defense planning and public safety. Part of the reason for this is that storms that are well away from land can only be monitored intermittently (e.g., three times per day). Infrasound signals are produced by the interaction of the hurricane with the sea-state and hold promise for characterizing sudden changes in hurricane strength on a time scale not possible with current sensing technologies. The University of Mississippi is leading a US national collaboration to monitor hurricanes using infrasound in the Gulf of Mexico and in the Western Atlantic Ocean. The results of measurements by from our group will be summarized, and the technical challenges associated with these measurements will be discussed.
Infrasonic precursor of tropical cyclone
Authors: Naugolnykh Konstantin A. , Rybak Samuil A.
Published: May 2008

Intense infrasonic emission was observed prior to the birth of a tropical cyclone (Netreba, 1991). It is connected apparently with instability of atmospheric layers in cyclone area. There are different mechanisms of this effect. Stratified compressional flow is unstable (Rybak, 2002), providing amplification of its potential component. Cooling of air in upward convection flow makes water vapor supersaturated. This is a nonequilibrium state of fluid where effect of instability can be developed. The equation of infrasonic propagation in such a medium is developed. (Naugolnykh, Rybak, 2006). Solutions of instability equation indicates the effect of radiation instability which produces infrasonic wave generation and its nonlinear evolution. Corresponding analyses of this equation make it possible to clarify the principally important aspects of cyclone infrasonic precursors. [Work supported by ESP.NR.NRCLG982524.]
Implications from the analysis of meteoric infrasound
Authors: Evers Laeslo G. , Haak Hein , Le Pichon Alexis , Antier Karl
Published: May 2008

Monitoring of infrasound has been widely applied in the past to detect nuclear tests. The Limited (Partial) Test Ban Treaty of 1963 confined nuclear test explosions to the underground marking the end of the global interest in infrasound. During the negotiation of the Comprehensive Nuclear-Test-Ban Treaty, in 1995-1996, it became gradually clear that infrasound monitoring should be become one of the four techniques for the treaty's verification system. The global interest in infrasound has increased significantly since the signature of the CTBT. Meteors are one of the few natural sources mimicking a nuclear. Therefore, it is an ideal object to test detection capability, phase identifiers, localization procedures and propagation models of infrasound and their processing techniques. In this presentation, we will show the results of studies on meteoric-generated infrasound and their implications for infrasound as verification technique. In addition, results of the 2007.09.15 meteor in Peru will be discussed which is one of the few meteoroids in recent times leaving an impact crater.
Locating infrasound events in wind with dense distributed arrays
Authors: Howard Wheeler , Dillion Kevin , Shields F. Douglas
Published: May 2008

Applications for infrasound suffer due to the presence of wind noise in the sensor data. Several techniques have been and are being used to mitigate the influence of wind noise in locating infrasonic signals of interest. One of these methods is the averaging of data from multiple sensors in a distributed array. A distributed array was employed to study infrasonic signals from airborne sources. Wind noise during testing masked the location of the infrasonic signals in the time domain. Postprocessing techniques using statistical measures for dense arrays were employed to recover the onset of the infrasonic events. Data from these tests and an explanation of the postprocessing techniques will be discussed.
Study of Infrasound Propagation from the Shuttle Atlantis using a large Seismic Network
Authors: Hedlin Michael A. , Degroot-Hedlin Catherine D. , Walker Kris , Drob Douglas , Zumberge Mark A.
Published: May 2008

Inclement weather in Florida forced the shuttle Atlantis to land at Edwards Air Force base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allowed us to test our ability to model infrasound propagation through the atmosphere to regional distances. We predicted shadow zones and arrival times using rays launched at right angles to the conical shock front surrounding the shuttle, and traced through a standard atmospheric model, as well as a global G2S model. Comparison of predictions vs observations shows agreement over much of the study area for both atmospheric specifications. To the east of the shuttle trajectory, there were no detections beyond the primary acoustic carpet. Infrasound energy was detected hundreds of kilometers to the west and northwest of the shuttle trajectory, consistent with the predictions of ducting due to the westward summer-time stratospheric jet. Both atmospheric models predict regions of ensonification alternating with shadow zones to the northwest. However, infrasound energy was detected tens of kilometers beyond predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds.
Guided waves in plates with linear variation of thickness
Authors: Predoi Mihai Valentin M. , Ech Cherif El Kettani Mounsif , Hamitouche Zahia , Petre Cristian Catalin
Published: May 2008

Guided waves represent promising nondestructive evaluation (NDE) techniques. Their advantage of long distance propagation is however hampered by complex wave scattering at each discontinuity along the investigated structure. These scattered waves can be used to locate and size possible defects. Theoretical investigation is a prerequisite step in the development of a NDE technique. Planar metallic structures with localized thickness variation imposed by design represent possible new industrial structures that could be tested using guided waves. The waves scattered at the region of variable thickness must be theoretically predicted and experimentally measured before any defect could be detected. Very few authors have investigated waveguides with continuous variation of thickness. Our previous numerical and experimental studies have proven the complexity of the scattering phenomenon in such cases. Among other remarks is the curved shape of the wave front. The present work investigates properties of the waves in the linear thickness variation region of the waveguide. A plain strain model, developed in polar coordinates is theoretically developed and numerically tested using specialized finite elements based algorithms. Specific properties such as stress and displacements fields are determined by numerical simulation at several frequencies and dihedral angles.
Development of a system using ultrasonic waves for assessing the quality of frying oil and salad oil during frying
Authors: Izbaim Driss , Faiz Bouazza , Hamine Adil , Taifi Naima , Moudden Ali
Published: May 2008

The design and construction of a real-time system is described with reference to applications in quality control of frying oil. This system, developed using the LabVIEW™ software, controls the ultrasonic velocity by receiving the signals backscattered by a recipient full of oil. Measurements on samples of frying oil and salad oil are described and the results of velocity measurements on a group of samples of varying frying time taken in 160 °C are reported. The new system is built around three main elements: acquiring the oil signals, automating the signals control, and several calculations to determine in real-time the phase velocity of the oil. The results obtained show the feasibility of assessing the quality of oils using ultrasonic waves through monitoring the frying process. This system can be used also to control other industry products such as the canned fish oil, milk, and the cement.
Simulating electrically evoked emissions in the cochlea
Authors: Meaud Julien , Grosh Karl
Published: May 2008

Electrical stimulation of the cochlea is a means for investigating the electromechanics of the organ. In this study, we use a mechanical-electrical-acoustic cochlear model to make predictions of the effect of intracochlear bipolar electrical stimulation on the basilar membrane velocity and stapes velocity. Bipolar stimulation provides for a localized means of stimulating the outer hair cells (OHC) and is a well-established technique for evoking otoacoustic emissions. We show that both fast, fluid-borne, and slow, fluid-structure waves are possible. Whether the fast or slow waves dominate the overall response depends on the level of activity in the cochlea, the frequency and location of excitation, and the boundary conditions at the stapes and round window. We show that forward propagating traveling waves may dominate the basilar membrane response even with intracochlear stimulation apical to the measurement site. These results bear direct impact on the interpretation of noninvasive measurements using otoacoustic emissions.
Does Norwich's Entropy Theory of Perception avoid the use of mechanisms, as required of an information-theoretic model of auditory primary-afferent firing
Authors: Nizami Iftikhar
Published: May 2008

Norwich et al.'s Entropy Theory (1975-present) stipulates that (1) the auditory receptor is uncertain about the stimulus' intensity, (2) uncertainty, given by the “entropy” H, relates to primary afferent neuronal firing-rate F as F=constant×H. H was calculated according to Garner & Hake (Psychological Review 58, 1951; after Shannon, Bell System Technical Journal 27, 1948) using Information Theory. H is available any time events, their outcomes, and the appropriate probabilities of occurrence are known, precisely because Information Theory ignores mechanisms, such as sensory transduction. Hence, any “information-theoretic” hearing model must avoid physiological mechanisms, and Norwich et al. claim to comply. But do they? The Entropy Theory was scrutinized for avoidance of physiological mechanisms. Norwich et al. stipulated throughout that (1) “We can envisage a steady sensory stimulus as a stationary stochastic sequence of microscopic sensory events” (Norwich & Wong, Annales de la Fondation Louis de Broglie 22, 1997), (2) those events (representing different intensities) are repeatedly sampled by the receptor. Sampling is a mechanism, not separable from transduction, the event's (presumed) “outcome”. Also, Norwich et al.'s attempts to separate events from outcomes produces inconsistent identification of “events.” The Entropy Theory is not an information-theoretic model of primary-afferent firing.
Slopes of psychometric functions for forward-masked tones with and without a suppressor
Authors: Yasin Ifat , Plack Christopher J.
Published: May 2008

The compressive nonlinearity defined by the basilar membrane (BM) input-output (I/O) function is evident in the slopes of psychometric functions for forward-masked tones. A suppressor tone may reduce compression by linearizing the compressive portion of the BM I/O function, or reduce cochlear gain without affecting the value of maximum compression. The present study compared slopes of psychometric functions obtained for a fixed low-level signal in the presence of a variable masker with or without a suppressor gated with the masker. Thresholds and psychometric functions were obtained for four normal-hearing listeners using a 2I-AFC task. The sinusoidal signal was a low-level 4-kHz tone (0-ms steady state, 2-ms cos2 ramps) masked by a sinusoidal masker (100-ms steady state, 2-ms cos2 ramps). The maskers were either on frequency (4 kHz) or off frequency (2.2 kHz) and were presented at masker-signal intervals of 20-100 ms. Initial analyses suggest that as masker levels increase, the slopes of psychometric functions become increasingly shallow (on-frequency masker) or remain relatively steep (off-frequency masker). The effect of a suppressor on the slopes of the psychometric functions appears to be minimal. Results will be discussed in the context of a cochlear model of peripheral nonlinearity.
Behavioral evidence for off-frequency compression at 4 kHz
Authors: Arifianto Dhany , Plack Christopher J.
Published: May 2008

Most behavioral techniques for estimating the basilar-membrane response rely on the assumption that the response to an off-frequency masker is linear at the signal place. To test this assumption, we modified the additivity of forward masking technique. The signal was a 4-kHz, 10-ms pure tone, presented at 10 dB sensation level. The maskers were 500-Hz-wide bands of noise centered on 1.5, 2, or 4 kHz. Masker 1 had a duration of 200 ms and was followed immediately by masker 2 with a duration of 20 ms. The masker 2-signal silent interval ranged from 10 to 60 ms. For each interval, the masker level required to mask the signal was determined, for each masker presented individually, and for the two maskers combined. In the combined case, the levels of the two maskers were set to be roughly equally effective, and adaptively varied together. Combining two equally effective maskers should produce a 3-dB reduction in masker level at threshold if the system is linear. A reduction greater than this indicates compression. Although compression was greatest for the 4-kHz maskers, compression was also observed at 1.5 and 2 kHz, suggesting that the assumption of a linear off-frequency response may not valid.
Exploring the psychophysical temporal effect in masking using a model of the auditory periphery
Authors: Jennings Skyler , Heinz Michael , Strickland Elizabeth
Published: May 2008

Under some conditions, normal hearing individuals can detect a short duration signal in a simultaneous masker at a lower signal-to-masker ratio when there is preceding stimulation (either a precursor or an extension of the masker). This effect has been referred to as overshoot or the temporal effect. It has been hypothesized the neural adaptation may account for some but not all of the temporal effect. Recent psychophysical data suggest that cochlear gain may decrease over the course of the masker and improve detection. This could be mediated by the medial olivocochlear reflex (MOCR). In the present study, a model of peripheral auditory processing [Zilany and Bruce, J. Acoust. Soc. Am. 120, 1446-1466 (2006)] using a d'-type metric was used to assess the relative contributions of these processes. Although the model includes neural adaptation, initial results indicate that it does not predict a temporal effect. The potential role of the MOCR will be simulated by decreasing the gain of the cochlear amplifier, to see if this will produce a temporal effect in the model predictions. [Work supported by NIH.]
Temporal integration functions of amplitude modulation depth discrimination: can multiple-looks model explain this
Authors: Lee Jungmee , Edwards Derek , Andrews Jennifer , Murray Heather
Published: May 2008

Lee and Bacon (1994) applied a multiple looks model (Viemeister and Wakefield, 1990) as a mechanism of AM depth discrimination when the carrier and the modulator were presented at the same time (gated condition). The model provided a reasonable prediction, but the performance (d') was underpredicted when the number of modulation cycles changed from two to four. They speculated that onset information loss due to gating with two modulation cycles lead to a greater improvement with four modulation cycles. Following this, one would expect that AM depth discrimination can be better predicted by the multiple-looks model for the condition where there is no loss of modulation information at onset. This study compared psychometric functions of AM depth discrimination with different modulation cycles for the gated and onset-only conditions (carrier was presented for 250 ms prior to the modulation to preserve onset information). The slop of the psychometric functions with two modulation cycles was shallower than those with greater modulation cycles for the gated condition, while the slop of the psychometric functions was similar for all modulation cycles for the onset-only condition. The data will be discussed with multiple looks model. [This work was supported by NIDCD Grant No. R03 DC06605-02.]
Modulation of the voice-cuing effect on releasing speech from informational masking
Authors: Xu Lijuan J. , Li Jingyu Y. , Huang Ying , Wu Xihong H. , Li Liang
Published: May 2008

In cocktail-party environments, familiarity or knowledge of target talker's voice is useful for reducing speech-on-speech masking (Yang et al., Speech Communication, 49, 892-904, 2007). In addition, the onset asynchrony between target speech and masking speech is an effective cue for unmasking target speech. The present study examined whether the voice-cuing effect can be modulated by either the degree of familiarity/knowledge of target talker's voice or the speech onset asynchrony. When target speech started one second after masking speech, prepresenting a priming sentence voiced by the target talker significantly improved the recognition of the target speech which was copresented with masking speech. However, reinforcing the familiarity/knowledge of the target-talker's voice did not further improve the recognition. When target speech and masking speech started at the same time, a single presentation of voice-priming speech did not change participants' speech recognition against masking speech unless the familiarity/knowledge of target-talker's voice was reinforced by either a learning procedure or repeated presentation of the target-talker's voice before testing. These results suggest that the voice-cuing effect on releasing speech from informational masking is graded, depending on both the degree of familiarity/knowledge of the target-talker's voice and the modulation by other cues such as speech-onset asynchrony.
Prediction and audio synthesis of vehicle pass-by noise
Authors: Bongini Estelle , Molla Stephane , Herviou Cédric , Habault Dominique , Poisson Franck
Published: May 2008

The European project SILENCE is dedicated to the reduction of railway and roadway noise in urban areas. Within this context, SNCF and LMA (Laboratoire de mécanique et d'acoustique, Marseille) collaborate into the subproject B to develop a pass-by sound simulation software. This global modelling tool will support parametric studies on the reduction of the noise of a train or a car pass-by, by providing standard indicators (time signature, equivalent sound pressure level) and sound samples. These sound samples are computed in B-Format, which allows, after a short postprocessing, to provide various listening formats (mono-aural, binaural, œ). The software is now operational and the sources characterisation has been carried out on an AGC bi-mode BOMBARDIER train and a passenger car. Equivalent sources have been defined in various operating conditions. Simulated pass-by indicators (signature, Leqtp(A)) in various configurations have been compared to measured one and show very good agreement. A perceptive validation has been carried out with listening tests, by indirectly comparing recorded samples corpus and corresponding simulated samples corpus. It shows that the arrangement made by the listeners of the simulated corpus and the arrangement of the recorded corpus are closely the same and are based on the same perceptive criterion.
An energy-based updated modal approach for the efficient analysis of large trimmed models
Authors: Lielens Gregory , Van Den Nieuwenhof Benoit , Acher Fabien , Coyette Jean-Pierre
Published: May 2008

Large trimmed models, widely encountered in the automotive industry, generally involve a body-in-white structure coupled to an acoustic cavity and covered by a set of trim components. Due to the large number of degrees of freedom of such models, the direct analysis in physical coordinates, though theoretically correct, is not feasible on current computers. The paper presents an alternative and efficient solution strategy in modal coordinates that relies on an update of the modal parameters of the car body and the acoustic cavity, based on the energetic behaviour of the trim components. The description of the trim component in terms of an energetic database simplifies the data exchange between the automotive manufactor and the trim provider. Furthermore, it enables a fast frequency analysis of various loadcases/trim scenarios and makes optimisation possible. The updated modal approach implemented in Actran/Trim is applied on a simplified car model on which various trim components are applied. The application shows how the stiffening, added mass and damping effects of each trim component can be derived from the energetic database and can guide an optimisation process.
Extremal harmonic active control of power
Authors: Micheau Philippe , Gauthier Jean-Philippe
Published: May 2008

The extremal harmonic active control of power consists to define an energetic criterion at the main harmonic and to extremalize it on-line by commanding a secondary source of power. The term extremal means that the optimal criterion value is reached with an on-line optimization algorithm. Without loss of originality, the context of rotating machines oscillation in synchronization with rotor position is used to illustrate this approach. A second commanded torque source, attached to the shaft, is used to control speed oscillation due to torque disturbance. Such configuration can be found in hybrid automotive for example. The energetic criterion can be the kinetic energy (for conventional active speed oscillation cancelling), the reactive power (to add a virtual flywheel on the shaft) or the active power (for energy harvesting to charge a battery). The optimization algorithm is the method of steepest descent implemented with implicit or explicit gradient computation. But, in the case of reactive power, the implicit controller is not practically achievable. The experimental results with a test bed show that the explicit controllers converge at the extremum of each criterion. To conclude, the presented explicit extremal controller is a good candidate to be used for energetic criterion control.
Variable area jet nozzle for noise reduction using shape memory alloy actuators
Authors: Mabe James
Published: May 2008

A significant reduction in noise and improved fuel consumption can be achieved by varying the area of a commercial jet engine's fan nozzle. A larger diameter at takeoff and approach can reduce jet velocity reducing noise. Adjusting the diameter in cruise, to account for varying Mach number, altitude, etc, can optimize fan loading and reduce fuel consumption. Boeing recently tested a scaled variable area jet nozzle capable of a 20% area change. Shape memory alloy actuators were used to position 12 interlocking panels at the nozzle exit. A closed loop control system was used to maintain a range of constant diameters with varying flow conditions and to vary the diameter under constant flow conditions. Acoustic data by side line microphones and flow field measurements at several cross-sections using PIV was collected at each condition. In this paper the variable area nozzle's design is described. The effect of the nozzle's diameter on its acoustic performance is presented for a range of Mach numbers and mass flow rates. Flow field data is shown including the effects of the joints between the interlocking panels.
Intelligent interfaces for sound insulation: Numerical and experimental optimisation
Authors: Batifol Cedric , Galland Marie-Annick , Ichchou Mohamed
Published: May 2008

Sound insulation is actually achieved thanks to passive multilayers. These ones are classically made of elastic, acoustic and poroelastic media. Good results are obtained in medium and high frequencies, but low frequencies disturbances still remain a problem. Indeed, local and global resonant behaviours of the panel, such as plate bending mode or the double-leaf phenomenon, occur and lower the performances. An active concept has already been proposed and validated. Piezoelectric components are added to the interface and act a secondary source aiming at minimising the sound transmitted. In this contribution, a double-plate system is studied. A reduced finite element model of an elementary cell is presented. This one relies on modal projection and classical component mode synthesis (CMS) procedures. This model is first updated and validated thanks to measurements performed on a dedicated test bench. The use of active control allows a 15 dB enhancement of sound insulation at low resonant frequencies. Numerical experiments are designed. Response surfaces are obtained thanks to kriging procedures. Finally, the configuration of the optimal interface is discussed in a physical point of view.
Active-passive multilayered panels for reduction of both acoustic reflection and transmission
Authors: Sitel Azzedine , Hu Ying , Galland Marie-Annick
Published: May 2008

The design of panels reducing both acoustic reflection and transmission for a wide frequency range is a problem of considerable practical interest for building or transport industries. Classically, these panels are made up of elastic plates bonded to poroelastic layers. Such structures are efficient in the middle and high frequency range but exhibit a lack of performance at low frequency. Hybrid passive/active cells previously developed at the LMFA have proved their efficiency for global noise reduction. They combine passive means (elastic plates, poroelastic material) and active control through a piezoelectric actuator to ensure high panel performance throughout the whole frequency range. In this paper, two systems are described. The first one is a multilayered panel combining two cells: the first cell on the emission side ensures high absorption, the second cell located at the rear face aims at reducing transmission. The second structure consists of a double-plate system using a microperforated plate on the emission side and an active plate on the transmission side. The performance of the two systems are examined through analytical or numerical simulations developed for plane waves and diffuse field conditions, and through experiments carried out for plane waves under normal incidence.
Secondary source distribution effect on active noise control robustness
Authors: Azarpeyvand Mahdi
Published: May 2008

Arrangement of secondary sources and microphones play an important role in effectiveness and robustness of any active noise control (ANC) system. This paper concerns effective distribution of secondary sources for a typical ANC system so that provides a robust and acceptable level of noise reduction for different types of primary source, namely monopole, dipole and multipole, radiating at 100 Hz and 250 Hz. Two sets of secondary sources are considered here: planar distribution, and dome-type distribution. Results have shown that utilization of planar distribution model leads to more effective and stable noise reduction for most of the cases, while using a dome-type set of secondary sources is not able to effectively reduce noise from dipole and multipole primary sources. In addition, it was found that implementation of dome-type arrangement is more difficult than the planar distribution and is also very likely to become unstable for some particular source arrangements (i.e., or mathematically ill-conditioned).
Maintainance vs. “loss” of the perceptual bias favoring natural reference vowels
Authors: Bohn Ocke-Schwen , Polka Linda
Published: May 2008

Previous infant vowel discrimination studies (Polka & Bohn, 2003) have shown that babies are perceptually biased to favor vowels with more extreme articulations such that a change from a more peripheral vowel (“natural reference vowel” - NRV) to a vowel located more centrally in the vowel space is less discriminable than a change presented in the reverse direction. Recent studies of adult vowel perception suggest that the universal bias favoring NRVs is maintained in the absence of specific language experience and but “lost” if native or non-native language experience causes a reset of the perceptual default favoring NRVs. This presentation reports on vowel discrimination experiments which examined whether absence or presence of specific vowel experience is related to maintenance or loss of this perceptual bias in Danish infants (age 6-12 months). For two Danish vowel contrasts, asymmetries were observed for younger infants, but not for infants older than 10 months. For an English vowel contrast that does not exist in Danish, the asymmetry was maintained in infants up to 12 months and in adult Danish listeners. Results confirm the assumption that the perceptual bias favoring NRVs is maintained throughout the lifespan unless specific vowel experience causes on override. [Work supported by the Danish Research Council for the Humanities.]
The effect of training in noise on foreign language consonant acquisition
Authors: Garcia Lecumberri M. Luisa , Cooke Martin
Published: May 2008

Formal exposure to second language sounds normally takes place in clean, laboratory conditions, but at issue is the transfer of such learning to everyday situations. Categories learned in non-natural settings may be fragile, raising the question as to whether learning in noise leads to greater category robustness. The current study compared two groups of Spanish learners of English who were trained in either quiet or noise backgrounds on a 24 consonant discrimination task. Learners' performance was measured in pre- and post-tests and monitored over the course of nine weeks' training. Both groups showed continual improvement during training with similar overall gains of 6-7 percentage points, suggesting that training in adverse conditions is as effective as in quiet. Tests involving consonant identification in quiet and noise revealed no significant differences in pre-post improvement between the two groups. However, voiceless obstruents benefited more from training in noise while voiced obstruents experienced more improvement when trained in a quiet background regardless of the testing condition (quiet vs noise). The noise-trained disadvantage is consistent with masking of voicing in noise, while the quiet-trained deficit for voiceless obstruents may derive from overgeneralisation during the acquisition of new contrasts.
The role of segmental and intonational cues in dialect discrimination
Authors: Vicenik Chad , Sundara Megha
Published: May 2008

Research indicates that adult listeners are able to use intonation to discriminate between two languages when one of the languages is familiar (Ramus and Mehler, 1999; Pijper, 1983). In this paper, we test adults to determine whether they use segmental or intonational cues to distinguish their native dialect from a foreign one. In three experiments, American English listeners were asked to categorize American and Australian English sentences when (a) segmental and supra-segmental cues are available, (b) sentences are re-synthesized with flat intonation, leaving only segmental cues, (c) segmental information is stripped away, leaving only intonation. Results will be discussed in the context of infant research demonstrating that five month olds are able to distinguish different dialects of the same language (Nazzi, Jusczyk, and Johnson 2000).
Effects of syllable structure on reaction times in a delayed naming task
Authors: Mooshammer Christine , Goldstein Louis , Tiede Mark , Nam Hosung , Gao Man
Published: May 2008

Syllable complexity has been found to affect the time the speaker needs for planning and initiating utterance production. Shorter latencies for complex onsets (CCV) as compared to simple onsets (CV) have been explained by effects of segment-specific biomechanical constraints at the level of motor execution, and by neighborhood density at the planning level. Within the framework of Articulatory Phonology, shorter planning latencies for CV syllables (compared to VC) have been attributed to quicker stabilization for tighter gestural coupling hypothesized for in-phase coupling of the onset consonant and release with the vowel. We attempted to test both onset complexity (C vs CC) and coda complexity (open vs. closed syllables) within a single experiment, so that we could evaluate the relative magnitudes of these effects and uncover potential interactions. To do so, American English monosyllabic words varying in syllable structure were presented using a delayed naming paradigm. The results replicated both effects, showing additive effects of roughly comparable magnitudes. Whether these effects are due to planning or motor execution will be tested by further simple naming and picture naming experiments.
Individual differences in perception of emotions from nonsense speech
Authors: Patel Sona A. , Shrivastav Rahul
Published: May 2008

Identification of the acoustic cues used to perceive emotions in speech is important for a number of applications including rehabilitation, natural speech modeling, and speech synthesis. In a recent experiment, Patel, Shrivastav, Harnsberger, and Shrivastav (2007) found that a four-dimensional solution accounted for 90% of the variance in similarity judgments for 19 emotional categories in nonsense speech. This solution was determined for averaged judgments across twelve listeners. The present study investigated individual differences in the perception of emotions for speech devoid of semantic information but rich in suprasegmental cues. Six male and six female listeners participated in a same-different discrimination test of a set of nonsense sentences produced in nineteen emotional contexts by two actors. Nonsense sentences were used in order to avoid any biases caused by semantics. The perceptual distance between each stimulus pair was computed in terms of d' values for each listener. These distances were submitted to a multidimensional scaling analysis using the INDSCAL algorithm. The INDSCAL analysis reports the best fitting solution for all listeners as a group, along with the weights assigned to each dimension by individual listeners. The results of this analysis will be presented.
Phonological representation of negation in Sakizaya
Authors: Shen Wen-Chi , Chiang Wen-Yu
Published: May 2008

This paper aims at investigating phonological representation of negation in Sakizaya, an endangered Formosan language in Taiwan. Defying Yaeger-Dror's “Cognitive prominence principles” (2003), Chiang (2006) examines negators in Saisiyat, a SVO language as English, and finds the sentential subjects are more prominent acoustically rather than negators. Thus, I will adopt Chiang's modal (2006) and analyze phonological representation of six negators in Sakizaya to see where the pitch accent falls. Besides, if falling on the negators, I will see whether it is because of either cognitive prominence properties or its sentence-initial position? Six informants (three male and three female), from 50-74 years old, participated in the experiment, recorded by DAT, analyzed by Praat and digitized at a 22050-Hz sampling rate. Affirmative and negative sentences are asked in Mandarin while the informants are instructed to translate them into Sakizaya. Besides, they are asked to produce iterative -ay sentences since the negator ca'ay is the most frequently used negator with higher prominent syllable -ay. The results show negators are more prominent in Sakizaya compared to sentential subjects. I conclude it is word order that influences the prominence of pitch contour since Saisiyat is an SVO language and Sakizaya a VSO one.