bluuebunny/crossref_metadata_2025 huggingface dataset:
Polar scans as a nonlinear acoustics tool
Authors: Vander Weide John M. , Declercq Nico F.
Published: May 2008

Nonlinear acoustic wave response provides a powerful means of assessing material properties. One very interesting area of application is testing for material damage. While an undamaged material may have a very linear acoustic response, damage such as crack formation creates strong nonlinearity with acoustic excitation amplitude. Many nonlinear acoustics techniques for nondestructive testing analyze the harmonic content in the wave scattered from a crack. A planar c-scan can be used in conjunction with the nonlinear acoustics techniques to provide defect detection and imaging. Polar scans are a complementary technique for damage assessment which has not yet found application in nonlinear acoustics. In the polar scan, the sound field in the hemisphere around a material point is measured and plotted to display a unique signature of local material properties. This work provides initial investigations into the use of the polar scan technique in nonlinear acoustics by detection of the second harmonic.
Detection of the nonlinearity evolution in concrete samples subject to quasi-static loadings
Authors: Antonaci Paola , Bocca Pietro , Bruno Caterina , Gliozzi Antonio S. , Masera Davide , Scalerandi Marco
Published: May 2008

The signature of nonlinearity in the elastic response of a specimen to an impingent ultrasonic wave is usually determined through Fourier analysis, which provides low amplitude signals, often below noise level. We suggest here an alternative, based on the amplitude dependence of the response of the system. Our procedure is conceptually simple and easy to implement. In addition, it keeps simultaneously into account the nonlinear signature effects on phases, amplitudes and frequencies of the response. The procedure is described and used to analyse the variation of the nonlinearity in a concrete bar subject to quasi-static loadings of increasing amplitude. The sensitivity of the approach allows to distinguish the compaction phase (up to a load of 30% of the rupture loading) from a microdamage progression (up to a load of 60%) and the pre-rupture phases.
Nondestructive tests of cylindrical steel samples using the ultrasonic projection method and the ultrasound transmission tomography method
Authors: Opielinski Krzysztof J. , Gudra Tadeusz
Published: May 2008

The paper presents some methods of NDT of cylindrical steel samples by means of ultrasonic projection (UP) method and ultrasound transmission tomography (UTT) method. Some ways of scanning were proposed, using different measurement geometries and rendering possible the characterization and visualization of the inner structure of steel samples by projection and tomographic images of measured acoustic parameters. The measurements proposed in the paper allow us to obtain at the same time the distributions of mean values of a number of acoustic parameters characterizing the structure of samples: the mean amplitude of the ultrasonic wave after running through the sample, the mean runtime on the transmitter-receiver path, and the mean decrease of the ultrasonic wave frequency after running through the sample. These parameters measured in the tomographic scanning setup from many directions around the samples allow us to reconstruct the distributions of the local values of acoustic parameters such as respectively: the ultrasonic wave attenuation coefficient, the group velocity of the ultrasonic wave, the derivative of attenuation coefficient along the frequency. The reconstructed distributions of the local values of acoustic parameters render possible the imaging of the samples' internal structure cross-sections, each of the parameters characterizing different features of the structure.
Use of point-source/point-receiver elastic waves in NDT-application
Authors: Korobov Alexandr I. , Odina Natalya I. , Abramova Anna V.
Published: May 2008

The ultrasonic automated experimental setup and technique for research of anisotropy of elastic properties of micro- and nanocrystalline metals and residual stresses are developed. Setup works in range of frequencies of 0.2-5 MHz. Accuracy of measurement of propagation time of elastic wave is equal to 0.2 ns, amplitude - 1%. Setup allows to make diagnostics of metals using volume, Raleigh and Lamb waves and to carry out scanning on linear and angular coordinates. Use of point source and receiver of acoustic waves and the high time resolution allows to carry out research of anisotropy and residual pressure with high spatial resolution. The x-y-coordinate device operated by personal computer, allows to carry out two-dimensional scanning of the sample by elastic waves with step of 10 micron. Experimental results of diagnostics of anisotropy of elastic properties in a number of microcrystalline constructional materials with residual stresses (alloys of aluminum and steel), and also a steel plate in the field of welded seam are presented. Significant anisotropy of elastic properties caused by these defects is revealed in investigated samples. The work is supported by RFBR.
Acoustic attenuation in silicon and silicon oxide
Authors: Onanko Anatolij P. , Lyashenko Oleg V. , Lyashenko Inna O. , Onanko Yurij A.
Published: May 2008

In the present work the non-destructive acoustic attenuation (AA) method of the technological control the structure defects of semiconductor plates after various dozes of the x-ray irradiation is developed. For measurement of temperature dependences of AA the method of resonant fluctuations of a plate on frequency 1.5 kHz was used at elastic deformation in vacuum. Measurements of temperature dependences AA in silicon plate a 460–470 micron thick after drawing a 600 nm layer of silicon oxide. Disk of a p-type silicon, doped B, orientation (100) with specific electroresistance 7,5 ohm⋅cm. The small maximums of AA were observed at temperature 346 K and 380 K. The main maximum of AA was observed at temperature 510 K. The affinity received by us of value of energy of activation 0,8 eV of AA at 510 K to energy of migration interstitial atoms 0,85 eV of silicon allows to assume the relaxation mechanism caused by reorientation interstitial atoms of silicon in dumbbell configurations.
In-situ measured Q- factor dependence from load in short and long time periods
Authors: Vilchinska Nora A.
Published: May 2008

Dynamic loaded large object is under research. Long time periods (8 years) measurements are made by variety loads: from quasi static till strong motion. Short time measurements start from quasi static and load goes step-by-step till strong motion- maximum loaded- and return in the same way to quasi static. This experiment longs 60 minutes. An assessment of material quality factor (Q-factor) in places of measurements was made taking into account the absorbed and emitted energy. The Q-factor for energy is calculated from RMS response spectra curves. The Q-factor and its changes in long time and short time experiments in some MPs are compared. The smaller is the Q-factor, the higher is the concentration of interior invisible cracks. Structural alterations, opening of fractures and their closure under load, and transitional processes are reflected in the spectra of emitted acoustic signals and in the nonlinearity of response Q-factor.
Sound propagation in viscoelastic pipe with liquid-bubble mixture
Authors: Levitsky Semyon , Bergman Rudolf , Haddad Jehuda
Published: May 2008

Propagation of acoustic waves in thin-walled polymeric tube with viscous liquid is investigated. Dynamics of the tube - liquid interaction is studied within conjugated quasi-one-dimensional formulation; the tube material is supposed to follow linear viscoelastic model with appropriate choice of the compliance function. It is assumed that the liquid contains fine air bubbles; the concentration of free gas is supposed to be small. Compressibility of liquid in the wave in the presence of bubbles can be almost entirely attributed to compressibility of the gas phase; it is accounted for within dispersion equation for bubbly liquid. Both heat and viscous losses are included in the phase interaction description at the liquid-gas interface. The resulting dispersion equation for the waveguide with liquid-gas mixture is studied in the long-wave range, where sound length is larger from the waveguide diameter. Results of simulations illustrate strong influence of the pipe mechanical properties and parameters of the gas phase on sound dispersion and attenuation.
Acoustic measurement of bubble size and position in an ink jet printhead
Authors: Van Der Bos Arjan , Jeurissen Roger , De Jong Jos , Lohse Detlef , Versluis Michel , Reinten Hans , Van Den Berg Marc , Wijshoff Herman , Stevens Richard
Published: May 2008

An acoustic measurement method of the volume and position of a bubble in an ink jet print head, is presented. The system is driven by a piëzo actuator. The actuator is also used as a sensor by measuring the current through the piëzo. The method used to determine the volume and position of the bubble is based on a linear model of the investigated system. This model predicts the current for a given position and volume of the bubble. The inverse problem is to infer the position and volume of the bubble from the measured current through the piëzo actuator. The solution of the inverse problem is demonstrated. Thus, an acoustical measurement method of these properties is obtained. The results from the acoustical measurement method correspond closely with results from optical measurements. This indicates validity of the presented method.
Experimental examination on the interactive force between two bubbles under ultrasound irradiation: Influence of the distance between two bubbles on bubble behavior
Authors: Fujikawa Takaaki , Yoshida Kenji , Watanabe Yoshiaki
Published: May 2008

The interactive force called the secondary Bjerknes force works among multiple bubbles under ultrasound irradiation, which results in the complicated behaviors of bubbles. In this study, we have experimentally examined the direction of the interactive force depending on the distance between two bubbles. When two bubbles vibrate individually, the direction of the interactive force depends on the phase difference between vibrations of these bubbles. In addition to this theory, considering the influence of the radiated acoustic wave from a bubble vibration on the other bubble vibration, Ida has pointed that this influence induces a change in the direction of the interactive force [M. Ida et al., Phys. Rev. E 67, 056617 (2003)]. In order to examine this theoretical prediction, the behaviors of both a free bubble and a bubble adhered to the polymer were observed under ultrasound irradiation, using a high-speed video camera. From the results, we found the reversal of the direction of the interactive force due to the variation in the distance between two bubbles. These innovative experimental results give an interesting point of view to understand the dynamics of multiple bubbles.
Destruction of the gas-filled capsule using effects of the collapsing bubble near the capsule
Authors: Miyabe Jun , Yoshida Kenji , Koyama Daisuke , Watanabe Yoshiaki
Published: May 2008

A new technique to destroy the gas-filled capsule is proposed, making use of the collapsing bubble near the capsule in the ultrasound field. At the moment of collapses under the ultrasound irradiation, the bubble causes flow and acoustic wave radiation. These phenomena are expected to assist the destruction of the capsule. We observed the effect of the bubble on this destruction, using a high-speed video camera which enables the real-time imaging. In this experiment, we use gas-filled capsule made of polyvinyl chloride. When no bubble was near the capsule at sound pressure of 60kPa, the capsule showed no vibration. However, in the presence of neighboring bubble, the capsule showed the destruction behavior of the deformation and the emission of internal gas. At higher sound pressure such as over 100kPa, the capsule showed above destruction behavior even if the bubble was not located near the capsule. In the presence of the bubble, however, the capsule was destructed in a shorter time. These experimental results give significant knowledge to a technique manipulating the gas-filled capsule destruction in the drug delivery system.
Complete characterization in thin film using picosecond ultrasonics and nanostructured transducer
Authors: Mante Pierre-Adrien , Robillard Jean-François , Devos Arnaud , Roch-Jeune Isabelle
Published: May 2008

Picosecond ultrasonics is an efficient method to excite and detect vibrations within a thin film. A strong optical pulse warms a material surface, which leads to the creation of an acoustic wave propagating at the sound velocity. The waves propagation modifies the optical properties of the material that can be detected by a second time-shifted optical pulse. With an usual metallic transducer, only longitudinal waves can be generated. The use of this technique on a nanostructured transducer adds in-plane propagating waves. In the case of an isotropic medium, we have access to all acoustic properties. In order to confirm this statement, we realized and studied 2D lattices of metallic nanostructures. We used e-beam lithography to obtain defect free lattices of aluminum nanocubes. Both cubes width and lattice parameters were chosen to optimize the properties measurements [1]. This nanostructuration allows us to get information about longitudinal and in-plane waves, in the gigahertz frequency range. The experiments where carried out with an aluminum lattice on a 600nm-thick silica film. This method, demonstrated on a well-known material, is suitable for any thin film. [1] J.-F. Robillard, A. Devos and I. Roch-Jeune "Time-resolved vibrations of two-dimensional hypersonic phononic crystals", Phys. Rev. B. 76, 092301 (2007)
Generation of acoustical phonons by femtosecond laser pulses in GaAs in the presence of external electric field
Authors: Babilotte Philippe , Ruello Pascal , Mounier Denis , Pugliese Daniel , Edely Mathieu , Bulou Alain , Breteau Jean-Marc , Gusev Vitali
Published: May 2008

Experimental results on the generation and the detection by fs laser pulses of the acoustical phonons at frequencies from tens to hundreds GHz in GaAs in the presence of external electric field are presented. The influence of the magnitude and the direction of the applied electric field on the parameters of ps ultrasound is investigated. Results obtained in GaAs and low-temperature GaAs are compared. The experimental opportunities to discriminate the acoustical phonons produced by laser-induced inverse piezoelectrical effect and the acoustical phonons due to the thermoelastic mechanism and to the mechanism of electron-phonon deformation potential are discussed. This study was supported by ANR project BLAN06-3-136284.
Temperature Dependence of Elastic Constant Measurements on Thin Films by Picosecond Ultrasonics
Authors: Emery Patrick , Devos Arnaud
Published: May 2008

The temperature dependence of mechanical parameters is well-known for bulk materials. New methods have to be developed to access such characteristics on thin films. These measurements are needed for understanding the temperature behavior of acoustic components in microelectronics, as for Bulk Acoustic Wave (BAW) resonators used in wireless communication. A BAW resonator uses the thickness mode resonance of a piezoelectric layer (Aluminium Nitride). In the radio-frequency range, a BAW resonator is a complex stack of various materials in thin film. The temperature dependences measurements offer a way to regulate the performances' drift induced by the warming of the device and to design temperature-independent components. Here, we present a method based on a variable temperature picosecond ultrasonics setup. The procedure is first validated on silica, then applied on various BAW technology materials (AlN, Mo, SiN, W).
Green chillies: a practical thermoacoustic refrigerator in day-to-day use since February 2007
Authors: Spoor Philip
Published: May 2008

CFIC, Inc. recently designed and built a thermoacoustic food refrigerator for the U.S. Army's Combat Feeding program (based at the Natick Soldier Center in Natick, MA). The Army wants a more combat-hardy alternative to standard vapor-compression devices, which have many leak-prone braze joints. However, the thermoacoustic "Army Fridge" has generated increasing commercial and public interest as the search for environmentally benign alternatives to conventional refrigeration has intensified. The Army fridge uses helium as its working fluid, and it has no pumps or cirulating fluids, only heat pipes and fans for heat exchange with the air. Unlike all other thermoacoustic prototypes known to us, this device is expressly designed like a product, with all the thermoacoustic hardware and controls confined to a relatively small enclosure on top of a large (17 cubic foot) cabinet, and operation accomplished by a single power switch and a thermostat. In early 2007 the Army fridge went into long-term testing at CFIC, Inc. as our auxiliary refrigerator. By March 2007 it will have surpassed 1 year (8760 hours) of continuous running. We will present details of construction, performance history, and recommendations for higher efficiency and lower cost.
LDV measurements of acoustic streaming in a traveling wave, closed-loop resonator
Authors: Desjouy Cyril , Lotton Pierrick , Penelet Guillaume , Blondeau James
Published: May 2008

The first part of this work deals with the study of an annular acoustic resonator, where the acoustic field is controlled by two loud-speakers in order to generate a purely traveling wave. The results of a complete electroacoustic modeling of this device, where the acoustic field is accurately defined, are compared to the experimental results. The second part deals with the characterization of various non-linear effects occurring in such a device. The generation of acoustic streaming is especially investigated in our study. Laser Doppler Velocimetry measurements are performed in order to characterize both first order (acoustic) and second order (acoustic streaming) velocity fields. Works are now in progress in order to improve accuracy of streaming measurement and to compare the experimental data to the available theories. This study should contribute to enhance the designing of thermoacoustic devices and should be also useful for its potential applications in microfluidics, especially for the development of micro-pumps and micro-mixers.
Weakly non-linear thermoacoustics for general porous media
Authors: In 'T Panhuis Peter , Rienstra Sjoerd , Slot Han , Zeegers Jos
Published: May 2008

A weakly nonlinear theory for thermoacoustics, including acoustic streaming, a temperature-dependent viscosity and slowly varying pores with arbitrarily shaped cross-sections, has been constructed by systematically applying dimensional analysis and small-parameter asymptotics. In this way a set of equations for the acoustic and streaming variables can be derived. For some simple cases explicit solutions can be found, such as the short-stack approximation, but for the more advanced applications we have to resort to a numerical solution. The theory has been implemented both for standing-wave and traveling-wave applications. For the case of a standing-wave system we have compared our computations with experimental data and found a remarkable agreement.
Physical mechanism and theoretical model of thermoacoustic heat exchangers
Authors: Luo Ercang , Gao Bo
Published: May 2008

Unlike a regenerator, there are both oscillating heat exchange flux (first order) and non-zero time-averaged heat exchange flux (second order) in the hot and cold end heat exchangers of thermoacoustic systems. The non-zero time-averaged heat flux just reflects the net heat exchange between the working substance and external heat sinks, which is more important and interesting for design. In this paper, the physical mechanism of oscillating flow heat exchanger is first analyzed. Based on understanding of the heat transfer mechanism, the theoretical model of heat transfer is then developed; in this part, the key of the problem is to obtain transversal distribution of the second order time-averaged temperature, T20(y). Eventually, an analytical expression of Nusselt number for the thermoacoustic heat exchangers is obtained under the assumption of laminar flow.
Role of temporal fine structure cues in speech intelligibility
Authors: Lorenzi Christian
Published: May 2008

A number of studies have investigated the role of two temporal features of the narrowband speech signals at the output of auditory filters in speech identification: temporal envelope (E) and temporal fine structure (TFS) cues. To assess the contribution of each feature to speech identification, speech stimuli were split into an array of contiguous analysis bands and processed using several techniques to remove, as far as possible, either E or TFS cues within each band. Overall, the outcome of these studies indicated that, after moderate to subtantial training, high levels of speech identification measured in quiet could be obtained for normal-hearing listeners on the basis of E cues or TFS cues alone. The results obtained with TFS cues only may appear surprising, because it is generally considered that, at least for non-tonal languages, E cues carry most of the phonetic information required for speech identification in quiet whereas TFS cues play mainly a role in conveying the pitch cues required for the segregation of speech and background sounds. Further work assessing the extent to which TFS cues alone can convey useful linguistic information in addition to these pitch cues will be reviewed.
Temporal fine structure coding for pitch and speech perception
Authors: Oxenham Andrew J.
Published: May 2008

Temporal fine structure can be defined mathematically with relative ease. Understanding its perceptual importance, or even how it is coded in the peripheral auditory system, is another matter. This talk will review recent work from our lab that addresses some of these issues. The focus will be on the use and representation of temporal fine structure in complex pitch perception with spectrally resolved and unresolved components, and on the importance of temporal fine structure when using F0 information in speech to segregate target speech for competing talkers and other complex interfering sounds. [Supported by National Institutes of Health grant R01 DC 05216.]
Discrimination of stochastic patterns of frequency modulation relevant to speech perception
Authors: Sheft Stanley , Lorenzi Christian
Published: May 2008

Recent work has suggested involvement of temporal fine structure (TFS) information in speech perception, especially in adverse listening conditions. However, little is known regarding discrimination of pattern of TFS modulation, an ability that would underlie robust contribution to speech processing. The present study evaluated the ability to discriminate among stochastic patterns of frequency modulation (FM). Contrasting modulators were different samples of lowpass noise that shared a common bandwidth and resulted in the same maximum frequency excursion. Performance levels declined in an orderly manner with modulator bandwidth, similar to results obtained when lowpass noise is used to modulate amplitude (i.e., AM) rather than fine structure. Modeling, however, indicated that the similarity was not simply a result of FM-to-AM conversion at the output of auditory filters. In additional conditions, discrimination of stochastic FM was measured in the presence of wideband noise which in some cases was sinusoidally amplitude modulated at either 4 or 20 Hz. With both unmodulated and modulated maskers, little effect on performance was noted, even with a signal carrier level as low as 15-20 dB above detection threshold. Absence of a substantial masking effect indicates availability of TFS cues for speech perception in noise. [Work supported by NIH.]
Facilitation of intensity discrimination of short stimuli in noise occurs not far from a stimuli detection threshold
Authors: Rimskaya-Korsakova Liudmila
Published: May 2008

Adaptation is a main property of sensory receptors. In a basis of adaptation are properties of peripheral receptors and central neuron. There is a question: what is the auditory adaptation mechanism to short high frequency stimuli? How the auditory system can trace stimulus amplitude changes? The probable answer is: stimuli are mixed with noise of different origin. Noise adapts hearing and improves discrimination of stimulus. Simulation researches of peripheral encoding were shown the amplitude structure of short stimulus acting in isolation or in noise could be preserved when intensity are not far from thresholds of fibers. For each stimulus level there is the certain noise level, when amplitude structure can be detected without losses. In this work the validity of these statements was checked up in auditory experiments. The thresholds of intensity discrimination (ID) for short stimulus presented in silence and in conditions of simultaneous and forward masking have been estimated. In a range of average stimulus intensity and for each stimulus level there is the certain noise level when ID is better in noise but not in silence. The ID facilitation is registered near to the stimulus detection thresholds and after adaptation of hearing by noise. Results of auditory researches correspond to the simulation results.
Hard times for the pitch of complex sounds in reverberant environments
Authors: Sayles Mark , Winter Ian M.
Published: May 2008

Reverberation is present in most everyday listening environments, with sound reaching our ears directly from the source(s), and indirectly after reflecting from nearby surfaces. Reverberation smears spectral transitions through time and disrupts temporal envelope modulation in harmonic complex sounds such as voiced portions of speech. Envelope modulation can provide a cue to the pitch of complex sounds and is relied upon by hearing impaired listeners. We have examined the effects of reverberation on the temporal representation of the dynamic pitch of frequency-modulated harmonic complex sounds in the responses of single units from the ventral cochlear nucleus. Without reverberation most units provide a strong representation of the modulated pitch in their short-term interspike interval distributions. Relatively mild reverberation degrades the representation based on envelope modulation, whilst more severe reverberation removes it. The representation of pitch based on fine structure is more robust to the effects of reverberation; however, this representation is smeared in time by indirect sound energy. The effects of reverberation are critically dependent on the neuron's best-frequency, source-to-receiver distance, fundamental frequency and frequency modulation rate. We observe comparable results in human listeners using the same sounds.
Charactering the individual ear by the "Auditory Profile"
Authors: Dreschler Wouter A. , Esch Van Thamar E. , Larsby Birgitta , Hallgren Mathias , Lutman Mark E. , Lyzenga Johannes , Vormann M , Kollmeier Birger
Published: May 2008

This paper describes a new approach to auditory diagnostics, which is one of the central themes of the EU-project HEARCOM. For this purpose we defined a so-called "Auditory Profile" that can be assessed for each individual listener using a standardized battery of audiological tests that - in addition to the pure-tone audiogram - focus on loudness perception, frequency resolution, temporal acuity, speech perception, binaural functioning, listening effort, subjective hearing abilities, and cognition. For the sake of testing time only summary tests are included from each of these areas, but the broad approach of characterizing auditory communication problems by means of standardized test is expected to have an added value above traditional testing in understanding the reasons for poor speech reception. The Auditory profile may also be relevant in the field of auditory rehabilitation and for design of acoustical environments. The results of an international 5-center study (in 4 countries and in 4 languages) will be presented and the relevance of a broad but well-standardized approach will be discussed.
Bernoulli coding on the auditory nerve and its implications for central auditory processing
Authors: Houde Robert A. , Hillenbrand James M.
Published: May 2008

The auditory periphery is well represented as a bank of band pass filter/inner hair cell (IHC) channels, with each IHC providing half wave rectification, amplitude compression, and conversion to firing probability on the auditory nerve (AN) fibers innervating that IHC. Frequency resolution varies dramatically with sound intensity, ranging from sharp tuning near threshold to very broad at high intensities. Cochlear filtering provides a satisfactory representation of broadband characteristics such as timbre but not the fine frequency resolution required for perceptual frequency discrimination. High resolution frequency analysis must, therefore, be provided by post-AN processes. We present a model of AN coding in which fine frequency analysis is carried out at central auditory stages. By this model the stochastic process on each AN fiber resulting from the IHC's firing probability is modeled by a Bernoulli process. As a result, the IHC output signal is transferred to the cochlear nucleus (CN) without further filtering, where it can be recovered by a simple summation over those AN fibers from the region of that IHC. We present a neurally plausible process for narrow band analysis at the CN using the regular pulses of chopper cells.
The first effect of pitch shift as a function of component spacing
Authors: Mielczarek Adam
Published: May 2008

The paper presents the results of an experiment regarding the influence of component spacing on the first effect of pitch shift. During the adjustment procedure, the listeners matched the pitch of the three-component complex to the same sensation produced by pure tone. The stimuli were composed of the 3rd, 4th and 5th harmonics of 100, 200 or 400 Hz shifted up in the frequency domain by 30 Hz. The level of each component was 50 dB SPL. The subject was presented with a 5-s sample of the test complex, and after a 500 ms break he had to define the pitch of the three-component complex using the matching tone. The results of the experiment suggest that the pitch shift phenomenon is based on the relative frequency rather than on the absolute frequency or the dominant component number.
Neuronal representation of pitch ambiguity
Authors: Sayles Mark , Winter Ian M.
Published: May 2008

Iterated rippled noise (IRN) is produced by delaying a broadband noise by time d, multiplying by gain g, adding the delayed noise to the original, and repeating this process for n iterations. When g=+1 IRN has a well-defined pitch at 1/d Hz. If g=-1 the pitch can be ambiguous. A gain of -1 is equivalent to applying a frequency-independent phase shift φ of π rads to the delayed noise (g=+1 ≡ φ=0). We recorded spike-trains from single units in the ventral cochlear nucleus in response to IRN with varying φ. Units with high best frequencies represented waveform envelope modulation (independent of φ), however, units in the phase-locking range of best frequencies represented stimulus fine structure (which varies with φ). Fine structure responders show a gradual transition from a well-defined peak in the interspike interval distribution at d when φ=0 to two equal-amplitude peaks flanking d when φ=π, and a gradual shift back to a well-defined peak at d as φ approaches 2π. Within the dominance region for pitch interspike interval distributions account for psychophysical pitch matches of 1.07/d and 0.94/d Hz for φ=π/2 and 3/2π respectively, as well as the ambiguous pitches of 0.88/d, 1.14/d, and 1/2d Hz heard when φ=π rads.
Temporal dynamics of stimulus specific processing in the human auditory cortex as revealed by electroencephalography
Authors: Briley Paul M. , Krumbholz Katrin
Published: May 2008

When the same sound is presented repeatedly, the electrical brain response recorded over the scalp decreases in amplitude, an effect known as adaptation. Adaptation is dependent on both the similarity of the sounds and the time between them. It has been particularly well studied for a deflection of the electrical response known as the N100, which peaks about 100 ms after sound onset and receives major contributions from auditory cortical sources. Adaptation may reflect decreased sensitivity to repetitive stimuli, but could also indicate more efficient processing of familiar events. Research on adaptation has often employed an alternating tone paradigm (A-B-A-B), examining the effects of changing inter-stimulus interval (ISI) or the frequency separation between A and B tones. Decreasing the frequency separation leads to an increase in N100 adaptation, and it has been suggested that the frequency specificity of this adaptation sharpens with decreasing ISI. In contrast, some studies have used A-B pairs with long inter-pair gaps and have found an enhancement of the N100 response to the B tone at short ISIs. In order to gain a better understanding of the processes contributing to adaptation and enhancement, this study investigates the temporal dynamics and the frequency selectivity of these effects.
An Investigation of Width and Depth Perception toward a Sound Image Constructed of Multiple Variant Sound Waves Emitted from a Loudspeaker Array
Authors: Yamakata Yoko , Kimura Toshiyuki , Naoe Munenori , Katsumoto Michiaki
Published: May 2008

Many musical instruments, including violins and guitars, vibrate their resonant bodies differently over their surface when they make a sound. This paper aims to reveal the influences of such vibration variation of a soundboard surface on the width and depth perception of the sound image when listeners were in a near-field 50 cm or 1 m away from the soundboard. In this paper, a loudspeaker array mimicked the surface vibration as each loudspeaker makes a corresponding sound independently and cooperatively. Three types of sounds, synthesized single-tone, multi-tone, and instrumental, were used as sources. To know what factors affect the perception of the sound image, various test sound sets were prepared by varying an original sound set in amplitude or delay for each frequency for each loudspeaker. Eight subjects were asked to identify which sound image in a pair of test sounds was wider or farther than the other according to Scheffe's pair comparison method. The results shows that a test sound set with a delay variation, which mimics sounds emitted by bending vibrations propagating on a soundboard, obviously influences the perception of sound image width and that the amplitude variation does not have much influence.
MEG Recordings of Amplitude-modulated Noise and Tonal Stimuli in Healthy Adult Listeners
Authors: Zhang Yang , Nie Yingjiu , Imada Toshiaki , Tanaka Keita , Kawakatsu Masaki
Published: May 2008

Amplitude modulation (AM) provides very important auditory information for the perception of complex sounds by normal listeners as well as cochlear implant users. The present study used a 122-channel whole-head magnetoencephalography (MEG) system to record auditory responses to amplitude-modulated pure tones and broadband noises in six healthy male adult subjects. The stimuli were presented in blocks of twenty with a brief silence in between, and the AM rates for both types of stimuli were at 20, 40, and 80 Hz. At least 80 artifact-free trials were collected for each stimulus. As expected, the MEG data showed a significant bilateral effect of AM rate in the N1m component. There was also strong evidence that the neural representations of both the unmodulated pure tone and noise stimuli in the auditory regions of both hemispheres could be significantly affected by the global context of block design stimulus presentation.
Speaker size discrimination for acoustically scaled versions of whispered words
Authors: Aoki Yoshie , Irino Toshio , Kawahara Hideki , Patterson Roy D.
Published: May 2008

Humans can extract the message from the voices of men, women, and children without being confused by the size information, and they can extract the size information without being confused by the message. This suggests that the auditory system can extract and separate information about vocal tract shape from information about vocal tract length. Smith et al. [J. Acoust. Soc. Am. 117(1), 305-318 (2005)], Ives et al. [J. Acoust. Soc. Am. 118(6), 3816-3822 (2005)], and Aoki et al. [ARO, 31st Midwinter meeting (2008)] performed discrimination experiments with acoustically scaled vowels, syllables, and naturally spoken words, respectively, and demonstrated that the ability to discriminate speaker size extends beyond the normal range of speaker sizes. Smith and Patterson [BSA Cardiff (2005)] demonstrated that performance on the size-discrimination task is only marginally reduced when the vowels are unvoiced. We extended these size-discrimination experiments to whispered versions of naturally spoken, four-mora Japanese words. The just-noticeable-difference for the whispered words was about 6 %, which is roughly the same as that for voiced words. The results show that voicing is not required for effective extraction of the size information. Research supported by JSPS Grant-in-Aid [B18300060] and the UK-MRC [G0500221].
Effects of modality-dependent cuing and eye movements on sound localization
Authors: Tomoriová Beáta , Andoga Rudolf , Kopčo Norbert
Published: May 2008

A previous study of visual and auditory hemispheric cuing in horizontal sound localization found modality-dependent effects of cuing resulting in biases in responses [Kopco, Tomoriova, Andoga, J. Acoust. Soc. Am. 121, 3094, 2007]. The previous study also suggested that some of the effects might be due to eye movements as eye fixation was not controlled. The goal of the current study was to isolate the attentional effects from the eye movement effects. An experiment identical to the previous one was performed, with the exception that the subjects were fixating the center of the audiovisual display. Localization performance was measured for transient auditory stimuli originating in the frontal horizontal plane. In most runs, a cue preceded the stimulus and indicated (correctly or incorrectly) the hemisphere (left vs. right) from which the subsequent target arrived. The cues differed by modality and the cue-to-target onset asynchrony. The listeners were instructed to focus their attention to the cued side. Compared to the previous study, a reduction in some effects was observed. However, modality-dependent biases in performance persisted, confirming that auditory spatial attentional control is modality dependent and operating on time scale of seconds. [Supported by the Slovak Science Grant Agency.]
Haircell non-functionality and dead regions in the cochlea: an exploring study
Authors: Warnaar Bastiaan , Dreschler Wouter A.
Published: May 2008

Dead regions (DRs) refer originally to regions in the cochlea without evoked electrical potentials due to non-functional inner hair cells and/or fibers of the auditory nerve. The focus of this study is to characterize hair cell non-functionality in the cochlea by means of psychophysical tests. A battery of tests was administered to a group of 13 subjects with a steep sloping tone threshold (>50 dB/octave) between 1 and 2 kHz and severe loss (>60 dB HL) at high frequencies. Psychophysical Tuning Curves (PTC) and Threshold Equalizing Noise (TEN) are the classical tests to diagnose dead regions. Both use as criteria the phenomenon of off-frequency listening. Based on the results of complementary tests like Notched Noise measurements (NN) and Otoacoustic Emissions (OAE), it is argued that off-frequency listening is not necessarily connected to loss of inner hair cells and/or nerve fibers. Furthermore, combination tones produced by well functioning outer hair cells at places of severe hearing loss (>60 dB HL) are found. This may be explained by the presence of a dead region, which is verified with PTC and/or TEN measurements in 3 out of 4 of the cases.
Neural coding of envelope and fine structure in noise degraded speech
Authors: Swaminathan Jayaganesh , Heinz Michael
Published: May 2008

Numerous perceptual studies have revealed that envelope is sufficient for speech perception in quiet, but that temporal fine structure (TFS) is required for speech perception in noise. However, the neural correlates of these perceptual observations remain unknown. The primary focus of the present work was to develop and evaluate neural cross correlation coefficient (CCC) metrics to quantify envelope and TFS coding in auditory-nerve responses to noise degraded speech. Shuffled auto- and cross-correlogram analyses were used to compute separate CCCs to quantify stimulus-related envelope and fine structure based on neural spike train data from a computational auditory-nerve model. The neural CCCs have a wide dynamic range as revealed by near-zero values for uncorrelated conditions and near-one values for correlated conditions based on broadband noise responses. Spectrally matched noise was systematically added to a speech sentence at different signal-to-noise ratios (SNRs). Initial analyses reveal that CCC_ENV > CCC_TFS for positive SNRs, whereas CCC_TFS > CCC_ENV for negative SNRs. Predicted effects of hearing loss on envelope and TFS coding will also be discussed. These neural metrics can be used to evaluate temporal coding of speech with implications for cochlear-implant and hearing-aid strategies. Supported by NIH-NIDCD.
Modelling of the cochlea response as a versatile tool for acoustic signal processing
Authors: Boone Marinus M. , De Vries Diemer , Andringa Tjeerd C. , Schlesinger Anton , Van Dorp Schuitman Jasper , Valkenier Bea , Van De Vooren Hedde
Published: May 2008

The inner ear or cochlea processes the acoustic signals that enter the oval window into a specific time-frequency pattern. Many acoustic signal processing methods are based on this behaviour. A fundamental method is to calculate this time-frequency response by solving the differential equation of the movement of the basilar membrane, followed by a visualisation of the excitation patterns in a time-frequency plot. For that purpose Continuity Preserving Signal Processing (CPSP) is a promising method. In the presentation an overview will be given of a project that is carried out by TUD (University of Technology Delft) together with RUG (University of Groningen) being sponsored by STW (Dutch Technology Foundation). The project divides into four sub-projects which are closely related: Automatic Keyword Spotting, Machine Analysis and Diagnostics, Speech Intelligibility Enhancement for Hearing Aids and Quality Assessment of Room Acoustics. Results that have been obtained in the project will be summarised. Detailed results of the sub-projects will be presented in separate presentations.
Improving speech intelligibility based on a conjunction of multiple perceptual models
Authors: Schlesinger Anton , Boone Marinus M.
Published: May 2008

The enhancement of speech intelligibility is crucial to the success of hearing aids and other speech transmission systems. Such systems often have to operate in real-world situations, in which noise, reverberation and competing talkers impair the signal-to-noise ratio and therewith the degree of intelligibility. Psychoacoustic and neuropsychological models progressively explain the working principle of the auditory path. In order to technologically achieve the mammalian hearing-performance, Computational Auditory Scene Analysis (CASA), a vivid field of research in acoustics, converts these models into technical approaches. Asking for neuropsychological evidence that underlies the extraction of sound-objects in reverberation and noise, two models are essential. These are echo-suppression, which is subject to the precedence effect, and modulation perception, performed by a neural mapping of time-information of the auditory input into a periodotopical organization. The models have been applied and successfully tested in enhancing the signal-to-noise ratio, respectively. In this work, we conjunct both models and obtain a temporal and lateral inhibition system, which successfully suspends interferences. An evaluation of the proposed approach verifies the consistency with psychoacoustical experiments of the precedence effect and modulation perception; the resulting speech intelligibility benefits considerably in acoustically adverse situations.
Tinnitus: one problem that can be solved
Authors: Mattia G. Mario
Published: May 2008

The author axplains the origin of idiopathic or subjective tinnitus. After more than ten years of research (at a personal centre and at Rome University "La Sapienza" Faculty of Medicine ...) we have solved more than 80% of tinnitus problems for a thousand people. We have found that the perceived sound can be a source of stress and can be recorded in the brain as "dangerous". We illustrate that a psychological and neurological rehabilitation implemented in a multifactors approach can give health and offer a new normal quality of life. With biofeedback EEG, EMG and GSR we are implementing our therapy. The biofeedback helps people understand the effects of stress on tinnitus and how to manage this stress to optimize performance and improve health. Previous studies have shown an enhancement of human performance and faster rehabilitation when physiological measures (respiration rate, heart rate, skin conductance, temperature, and surface electromyography) were fed back in sessions of Autogenic Training.
Subjective experiment on auditory localization for traffic alarm sounds
Authors: Yokoyama Sakae , Tachibana Hideki
Published: May 2008

When riding a motorbike with a helmet or driving a car, it is often experienced that the judgment of directions of alarm sounds like a horn and sirens of engine truck and ambulance car becomes difficult. This kind of auditory localization is seriously related to traffic safety. In this study, therefore, the effects of covering the driver' s head with a helmet and sound transmission into a car on the auditory localization for traffic alarm sounds were examined by laboratory tests. To simulate a 3-dimensional sound field, the 6-channel recording/reproduction technique was applied and the incident direction of the test sounds was varied in twelve horizontal directions.
Problems in sound quality evaluation in Brazil: general or cultural ones
Authors: Paul Stephan
Published: May 2008

Within modern sound engineering the individual perception of sound events has to be considered. Within sound and vibration related research all over the world several instruments were already developed, but this instruments are subject to several restrictions, especially their language. When sound evaluations are to be made in Brazil adequate evaluation instruments are necessary. This article is intended to discuss some of the problems encountered by the author and its co-workers when developing assessment procedures and especially instruments for evaluation of sound quality with Brazilian subjects. Especially the work undertaken to study descriptors for sound and vibration and the problems resulting in this work will be discussed. We consider the present congress, with participants from all over the world, to be a suitable platform to discuss some of the problems and results obtained.