bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification and characterisation of the scholte A and circumferential S0 waves from the time-frequency analysis of an acoustic experimental signal backscattered by a tube
Authors: Latif Rachid , Aassif Elhoucien , Laaboubi Mustapha , Moudden Ali , Maze Gerard
Published: May 2008

The problem of the acoustic diffusion by a tube is a theoretical problem which had known since few years a considerable interest. A good comprehension of the acoustic diffusion makes it possible the study of the opposite problem. Many theoretical and practical works were made by a tube in the acoustic diffusion field. These works showed in particular that the resonance phenomenons are directly related to the physical and geometrical properties of the target. The interest of the study presented in this paper is the identification of the circumferential wave. Several frequential analysis techniques were applied to characterize the target. These analysis techniques currently used present the major disadvantage to not be able to highlight the temporal structure of the field diffused by the target. Reciprocally the acoustic temporal analysis of the target ca not always separate the successive arrivals of the various type waves in the signal and to have information on their frequential contents. The joint time-frequency representations provide this need. In this paper, the time-frequency of Wigner-Ville is applied to analyse the acoustic experimental signal backscattered by a steel tube with radii radio b/a=0.97 (a: external radius, b: internal radius) immersed in water. Through the Wigner-Ville image we have identified the scholte A and the circumferential S0 waves.
Study and development of a low-frequency acoustic sensor dedicated to the vibratory analysis and the mechanical characterization of the plates
Authors: Nassar Georges , Merheb Bassam , Skaf Alain , Lefebvre Fabrice , Nongaillard Bertrand
Published: May 2008

A low-frequency acoustic method was implemented for the purpose of nondestructive control and evaluation of metal plates coating. In this method, a mechanical pulse (acoustic impact) is used to generate acoustic vibrations on a frequency band between 100 Hz to 20 kHz, and a compact acoustic sensor, constructed with by composite materials with an embedded ferroelectric disk, is used to receive the acoustic vibrations. The technique consists in setting in resonance the integrality of a reduced size mechanical structure. The modal frequencies of plates are calculated by two methods: analytically and by finite element method. Then, a numerical modeling of the acoustic behaviour of the sensor is presented. Finally, experimental trials are described and results showing the sensitivity of the method to evaluate coating of metal plates are analyzed.
Lamb and Stoneley wave interactions with a fluid droplet
Authors: Martinez Loic , Wilkie-Chancellier Nicolas , Glorieux Christ
Published: May 2008

In order to analyse wetting aspects from an acoustical point of view, the present work investigates the interaction of a liquid droplet with Lamb and Stoneley waves propagating on a plane plate. A horizontal plane plate is in contact with a liquid on its lower interface, air in contact with its upper interface, the droplet lying on the top interface. Lamb waves are generated by a pulse trough a contact transducer placed at one edge of the plate. This generates in a wide range the high wave numbers of the Lamb modes A0, A1, S0 and the fluid born Sholte Stoneley wave (A-wave). For low wave numbers, the transducer is placed at normal incidence, under both the plate and the droplet. Signals obtained by emission/reception with the same transducer (2 MHz) clearly exhibits a coupling effect between acoustic modes inside the droplet and Lamb modes. Laser Doppler scans around the droplet show reflection/refraction/diffraction patterns of the incident line wavefront through the droplet. These experiments carried out with various wetting conditions point out a good correlation between the parameters of the acoustical resonances and the wetting properties, enabling an acoustic estimation of the wetting in a wide frequency range.
Miniature, high efficiency transducers for ultrasonic flow meter applications
Authors: Joshi Shrinivas G. , Zaitsev Boris D. , Kuznetsova Iren E.
Published: May 2008

This paper is concerned with the development of novel, miniature, high efficiency transducers for use in ultrasonic flow meters. Theoretical and experimental work done in our laboratory has shown that a flat, planar transducer that has minimal protrusion into the flow pipe can be realized based on conversion of plate acoustic waves (PAWs) to bulk acoustic waves (BAWs) and vice versa. The transducer is essentially a thin plate of a suitable piezoelectric material on which intedigital transducers (IDTs) are fabricated to generate and detect plate acoustic waves. With proper design very efficient conversion of energy from plate waves in the piezoelectric material to bulk waves in the fluid (and vice versa) can be achieved. For example, using lithium niobate as the piezoelectric material and water as the fluid, total conversion loss (PAW to BAW and back from BAW to PAW) of less than 2.5 dB has been obtained. An important advantage of plate waves is that since wave energy is present on both plate surfaces, the IDT can be on the surface opposite from that which is in contact with the fluid. Details of the theoretical analysis used, experimental results obtained, and potential applications will be presented.
Free-field calibration of microphones: theoretical and experimental determination of the acoustic center
Authors: Rodrigues Dominique , Durocher Jean-Noel , Bruneau Michel , Bruneau Anne-Marie
Published: May 2008

The concept of acoustic center is closely linked to the free-field calibration of microphones and have a great influence on the final results for the free-field sensitivity of the calibrated microphones. The international standard IEC 1094-3 defines the acoustic center of a reciprocal transducer as the point from which spherical waves seem to be diverging when the transducer is acting as a source. In the literature, the principal procedure used to measure the acoustic center of a reciprocal transducer is based on the measurement of the modulus of electrical transfer impedance at various distances of three pairs of microphones coupled by a free field. This paper presents a new procedure to determine the acoustic center of a reciprocal transducer assuming a source without any acoustic center and measuring the modulus of the electrical transfer impedance at various distances between this source and the transducer to be tested. Finally, the position of the acoustic center is deduced from the inverse distance law. Experimental values are presented and compared with theoretical values obtained using a theoretical model of the laboratory standard microphones (mounted on a semi-infinite rod) derived from those available in the literature.
Analysis of the backscattered waves in an heterogeneous material: Application on concretes
Authors: Garnier Vincent , Morières Stéphane , Chaix Jean-François , Corneloup Gilles
Published: May 2008

In heterogeneous materials, ultrasonic waves can be scattered forward or backward. The set of the backscattered contribution generates a wave that is attenuated over time. We make the measurement of this attenuation with the envelope of the backscattered signal. This information evolves with the nature, shape, and size of the scatterers so with the material state. First, we propose the simulation of the signal in which we introduce the attenuation dependence on the frequency. Second, we develop this application on concretes in which many scatterers contribute to the signal's generation. We apply the technique with differents tools to generate and exploit the backscattered waves. The attenuation evolutions with the material's nature, porosity, damage and saturation rate of the concrete are analysed.
Airborne phased array for airborne applications based on cellular polymer
Authors: Degel Christian , Becker Franz Josef , Heinz Martin , Fonfara Heinrich , Lemor Robert M.
Published: May 2008

Object recognition, advanced distance measurements and other inspection scenarios have an increasing demand in versatile airborne ultrasonic phased arrays for acoustic scanning without moving parts. Based on cellular polymer film with high piezoelectric effect we have realized an array structure with a pitch of 0.5 mm and element length of 10 mm. The working frequency of the material was measured to 250 kHz. From pointspread simulation with the small ratio of pitch/wavelength of 0.35 we could expect good beam steering and focusing characteristics. A first test array was realized and characterized. There was good agreement between measurement results and simulations. Additionally a low frequency electronic beamformer system was developed for generating the first B-image of an airborne phased array. Measurements showed that cellular polymer is a well suitable material for airborne applications. It can easily be structured to the desired shape. It allows especially the realization of phased arrays for applications like surface or profile measurement, access control, attendance check, robot guidance etc. New airborne array types like linear, phased, curved, or circular arrays are now possible. Also single element transducers with varying apertures (rectangular, oval), shaped apertures [focusing (line- or point-focusing), defocusing] or combinations of both are possible.
Nonlinear focal shift in focused ultrasonic transducers and its dependence on the Fresnel number
Authors: Makov Yuri , Sánchez-Morcillo Victor , Camarena Francisco , Espinosa Víctor
Published: May 2008

In this work we present a systematic study of the on-axis location of the maximum pressure and intensity points in the field radiated by a focused transducer. We report the motion of these characteristic points as the transducer voltage is increased. Different initial distributions, ranging from uniform to Gaussian cases, are considered. The numerical analysis is based on the solutions of the KZK equation with different initial conditions. Experimental results have been obtained for three different Fresnel number focused transducers in linear and nonlinear regime in order to analyze the focal shift effect. An analytical expression of the initial (linear) shift of the maximum pressure position is given. This expression, and the results of the numerical simulations, shows a good agreement with the experimental data. As a main conclusion, we demonstrate that the axial range of the nonlinear shift of pressure is larger for strong initial focal shifts, occurring for small Fresnel number transducers. Theoretical and numerical predictions of the focal shift effect in Gaussian beams are also presented. In this work we have established the relation between the focal shift (both in linear and nonlinear regime) with the Fresnel number of the transducer.
Influence of low temperature cycles on the integrity of pretreated 2024 T3 aluminium joints by an ultrasonic method
Authors: Rousseau Martine , Vlasie Belloncle Valentina
Published: May 2008

Many authors have considered the problem of adhesive bond durability over a long period of time or under special environmental conditions, and all have conclued that surface preparation is of paramount importance. Here, 2024 T3 aluminium alloy bonded joints, whose metallic plates underwent phosphoric acid pretreatment prior to bonding, are investigated before and after exposure to -40 °C for 67 h. This procedure of ageing is repeated several times and the samples are examined by ultrasonic Lamb waves after each cycle. In particular, the position of the cutoff-frequencies of ultrasonic guided waves which propagate into the bonded aluminum/epoxy/aluminium structure allows us to calculate the stiffnesses of the metal/adhesive interfaces with a rheological model. Thus, after exposure, a progressive decrease in the value of the stiffnesses is observed even for pretreated surfaces. Two complementary mechanical explanations are proposed. First, the cold exposure of the sample and the difference between thermal dilatation coefficients of aluminum and epoxy produce a damage of the interfacial zone. Second, the cooling introduces microcracks in the epoxy then caracterized by a smaller Young modulus.
Frequency modulated harmonics induces informational masking of Chinese speech
Authors: Wu Xihong H. , Chen Jing , Zou Xuefei F. , Li Jingyu Y. , Xu Lijuan J. , Li Liang , Chi Huisheng S.
Published: May 2008

Informational masking (IM) occurs when target speech is co-presented with competing speech. It is important to know what acoustic characteristics of a speech masker are essential to induce IM. This study investigated whether frequency modulation (FM) of speech is associated with IM. Nonsense Chinese Mandarin sentences were spoken by a young female as target stimuli and maskers were tone harmonics whose fundamental frequency (F0) was modulated sinusoidally and number of harmonic streams was varied. The magnitude of IM was evaluated by measuring the precedence-induced releasing effect of perceived spatial separation on target speech. The results show that the releasing effect reached the highest level when F0 became 252 Hz, which was the mean pitch of target speech. In addition, the releasing effect was significantly higher when the masker contained two harmonic streams than when one stream. These results suggest that because frequency-modulated harmonics can be used to inducing IM of speech, the FM component of speech is an important acoustic factor underlying IM. [Supported by the NSFC 60435010; 60535030; 60605016; 30670704.]
Across-frequency integration of speech information in listeners with sensorineural hearing loss
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: May 2008

At very poor signal-to-noise ratios, good speech perception may depend critically upon the ability of the listener to combine relatively brief glimpses of the signal that are separated both in terms of frequency and time. This presentation will review past research that has addressed the ability of normal-hearing and hearing-impaired listeners to integrate speech information in this way. The presentation will also consider recent studies from our laboratory that have investigated spectral/temporal integration of speech signals in listeners with mild-to-moderate sensorineural hearing losses. One of these studies focused upon the integration of speech information that was asynchronous across frequency and the other focused upon the integration of synchronous information arising from two relatively narrow bands that were widely separated in frequency. The results from these studies indicated that although the hearing- impaired listeners exhibited some characteristics suggestive of poor processing of speech, there was little indication of essential deficits in the ability to integrate synchronous or asynchronous across-frequency speech information.
Testing coherent reflection in chinchilla
Authors: Shera Christopher A. , Tubis Arnold , Talmadge Carrick L.
Published: May 2008

Coherent-reflection theory explains the generation of stimulus-frequency and transient-evoked otoacoustic emissions by showing how they emerge from the coherent “backscattering” of forward-traveling waves by mechanical irregularities in the cochlear partition. Recent published measurements of stimulus-frequency otoacoustic emissions (SFOAEs) and estimates of near-threshold basilar-membrane (BM) responses derived from Wiener-kernel analysis of auditory-nerve responses allow for comprehensive tests of the theory in chinchilla. Model predictions are based on: (1) an approximate analytic expression for the SFOAE signal in terms of the BM traveling wave and its complex wave number; (2) an inversion procedure that derives the wave number from BM traveling waves; and (3) estimates of BM traveling waves obtained from the Wiener-kernel data and local scaling assumptions. At frequencies above 4 kHz, predicted median SFOAE phase-gradient delays are in excellent agreement with the SFOAE measurements. At frequencies below 4 kHz, chinchilla SFOAEs show strong evidence of interference between short- and long-latency components. Approximate unmixing of these components, and association of the long-latency component with the predicted SFOAE, yields close agreement throughout the cochlea.
Two-tone suppression of stimulus frequency otoacoustic emissions in human ears with sensorineural hearing loss
Authors: Keefe Douglas H. , Ellison John C. , Fitzpatrick Denis F.
Published: May 2008

Two-tone suppression (2TS) of stimulus frequency otoacoustic emissions (SFOAEs) recorded in normal-functioning human ears is a noninvasive measure of cochlear nonlinearity. This study investigates 2TS SFOAE response properties in 63 subjects with sensorineural hearing loss and normal middle-ear function. SFOAEs were measured using tones at frequencies (fp) from 0.5 to 8 kHz and levels from 40-60 dB SPL. For interpreting SFOAEs, hearing status was classified at each frequency according to degree of hearing loss, with losses ranging from within normal limits to 95 dB HL. SFOAE suppression was measured as a function of suppressor frequency (fs) and level (Ls), with results analyzed in terms of a SFOAE suppression tuning curve. A tip-to-tail difference (TTD) was defined between the Ls needed to produce a criterion decrement in SFOAE level at fs one octave below fp and the Ls needed to produce a criterion decrement near fp. The TTD estimates cochlear-amplifier gain in normal-functioning ears, but its properties in impaired ears based on SFOAEs have not been examined. Results will be analyzed as a function of the hearing status to assess the relative impact of outer-hair cell dysfunction in the SFOAE source region at tonotopic place. [Work supported by NIH.]
Using the frequency dispersive properties of otoacoustic emissions to facilitate separation of different components
Authors: Long Glenis R. , Talmadge Carrick L.
Published: May 2008

Otoacoustic emissions (OAE) are frequency dispersive (different frequencies have different latencies), because of the properties of the basilar membrane. These frequency-dependent latency differences, are used to separate the transient otoacoustic emissions (TEOAE) from the stimulus, but have not been used with stimulus frequency (SFOAE) and distortion product (DPOAE) otoacoustic emissions. If continuously-sweeping tones are used to generate DPOAE and SFOAE, the frequency dispersive properties of these OAE cannot only be used to separate the evoking stimuli from the OAE, but also to separate OAE coming from different cochlear regions. Modifications of the LSF procedure to extract OAE (Long &Talmadge, 1997: JASA, 102:2831-2848; Talmadge et al. 1999: JASA,105:275-292) permit not only the extraction of the different OAE components, but also provide an estimate of the latency of the OAE, which does not depend on group delay. DPOAE and SFOAE extracted using sweeping tones in normal and impaired adults and infants provide information about the nature of cochlea function in these populations
Hemispheric Laterality and Peripheral Auditory Asymmetry studied by Transiently Evoked Otoacoustic Emissions
Authors: Moulin Annie M. , Nottet Jean-Bertrand
Published: May 2008

A peripheral left-right assymetry has been shown at the cochlear level: Transiently evoked otoacoustic emissions (TEOAEs) amplitudes are greater in the right ear than in the left ear of right-handed subjects, whereas no difference is obtained in left-handed subjects (Khalfa et al., 1998). This study sought to investigate a possible link between peripheral auditory assymetry and hemispheric laterality assessed by a dichotic listening task. Peripheral auditory laterality was investigated by comparing TEOAEs from both ears of each subject in 289 normally hearing subjects, with 94 left-handed subjects (52 women), and 194 right-handed subjects (129 women). Results show significantly greater OAE amplitude in right ear than in left ears for both right-handers (12.93 dB, SD=4.46 versus 11.89, SD=4.6) and left-handers (11.62 SD=3.8 versus 10.44, SD=3.8, whereas average hearing loss across frequencies did not show any significant difference. However, in the left-handers, only the subgroups of subjects presenting a right-ear advantage at the dichotic tasks, presented a significantly greater TEOAE amplitude in the right ear versus the left ear. Those results suggest a definite link between peripheral auditory assymetry and hemispheric laterality.
A psychophysical test of the Kummer primary-level rule for measuring distortion-product otoacoustic emission input/output functions
Authors: Lopez-Poveda Enrique A. , Johannesen Peter T.
Published: May 2008

The standard procedure for measuring distortion-product otoacoustic emission (DPOAEs) input/output (I/O) curves involves using primaries whose levels conform to the rule of Kummer [Kummer et al., J. Acoust. Soc. Am. 103, 3431-44 (1998)]. The assumption is that the DP originates at the F2 cochlear site and primaries that conform to this rule produce equal excitation at that site, which maximizes the DP amplitude. These ideas were tested psychophysically by measuring temporal masking curves (TMCs) for masker frequencies equal to the primary frequencies. A TMC-based level rule was obtained by plotting the levels of the F1 masker against those for the F2 one for corresponding masker-probe intervals. DPOAE I/O curves were then measured using the Kummer rule, the TMC-based rule, and primary levels optimized individually to maximize DP amplitude. DPOAEs for the TMC-based and the Kummer rule had statistically similar amplitudes, but they were both lower than those measured with individually-optimized levels. This undermines the assumption that maximum DP responses occur for primaries that produce equal excitation at the F2 cochlear site. Individually-optimized levels showed that L1 should be higher than prescribed by the Kummer rule. [Work supported by IMSERSO-131/06, PROFIT-CIT-390000-2005-4, and MEC-BFU-2006-07536, and The Oticon Foundation.]
Cochlear nonlinearity in normal-hearing subjects as inferred psychophysically and from distortion-product otoacoustic emissions
Authors: Johannesen Peter T. , Lopez-Poveda Enrique A.
Published: May 2008

The aim was to investigate the correlation between estimates of compression ratio, compression threshold, and cochlear gain for normal-hearing subjects inferred from temporal masking curves (TMC) and distortion-product otoacoustic emission (DPOAEs) input-output (I/O) curves. Special care was given to reduce the influence of DPOAE fine structure on the I/O curves. Data were collected for 10 subjects and for cochlear places with characteristic frequencies (CFs) of 0.5, 1, 2, and 4 kHz. Except at 4 kHz, little correlation was found between ratio estimates obtained with the two methods. One reason is that the DPOAE I/O curves show plateaus or dips which result in unexpectedly high compression estimates. Moderately high correlation was found between the compression-threshold estimates obtained with the two methods, although DPOAE-based values were systematically lower than those based on the TMCs. Both methods confirmed that compression ratio and threshold are approximately constant across the CF range considered. Cochlear gain could be estimated from TMCs only and it was found to increase slightly with increasing CF. It is discussed that DPOAE I/O curves may be inappropriate to infer precise individual nonlinear cochlear characteristics in normal-hearing listeners, particularly at low CFs [Work supported by IMSERSO 131/06, PROFIT CIT-390000-2005-4, MEC BFU-2006-07536, and The Oticon Foundation.]
Recovery of distortion product otoacoustic emissions (DPOAE) with high time-resolution from a moderate monaural-exposure to 2-kHz in human subjects
Authors: Aranda De Toro Miguel Angel , Ordoñez Rodrigo , Reuter Karen , Hammersho/i Dorte
Published: May 2008

The amplitude of distortion product otoacoustic emissions (DPOAE) decreases temporarily after exposure to a sound of moderate level. These changes show similarities to the changes observed in absolute hearing thresholds after similar sound exposures. This paper presents the experimental protocol to study how DPOAEs in human subjects are affected after a monaural exposure of ten minutes to a pure tone of 2 kHz. The experimental protocol allows to measure fine structures of the DPOAE with high time-resolution in a limited frequency range. Thus, the results give a detailed description of the DPOAE recovery process and can be used to develop a mathematical model of the recovery. This is the first approximation to study the recovery of more complex exposures. [Work supported by the Danish Research Council for Technology and Production.]
Analysis of time-frequency fine structure of transiently evoked otoacoustic emissions to study the effects of exposure to GSM radiofrequency fields
Authors: Paglialonga Alessia , Tognola Gabriella , Parazzini Marta , Sibella Federica , Bell Steven L. , Lutman Mark E. , Thuroczy Gyorgy , Ravazzani Paolo
Published: May 2008

Mobile phones have become very commonly used throughout the world within a short period of time. To date there is only limited knowledge about interaction between electromagnetic fields (EMFs) emitted by mobile phones and the auditory function. Moreover, there is widespread concern that there may be potential for harm. The aim of this study, performed in the framework of the European Commission Project GUARD “Potential adverse effects of GSM cellular phones on hearing” (5FP, QLK4-CT-2001-00150, 2002-2004), was to assess potential subtle changes in cochlear function of normal hearing subjects by measuring the time-frequency fine structure of TEOAEs after exposure to low-intensity EMFs emitted by GSM mobile phones. TEOAEs were recorded in 27 healthy young adults before and after 10 min of real or sham exposure in a double-blind design. TEOAE data were analyzed both globally (broadband analysis) and using the wavelet transform (analysis of time-frequency fine structure). The broadband analysis revealed no significant effect on TEOAEs related to exposure, confirming results of previous studies; in addition, no significant change was detected in the analysis of the elementary wavelet components, suggesting that a 10-min exposure to EMFs emitted by GSM mobile phones has no immediate after-effect on TEOAE time-frequency fine structure.
Potential adverse effects of UMTS electromagnetic fields generated by mobile phones on the human inner ear: A European project (EMFNEAR)
Authors: Moulin Annie M. , Parazzini Marta , Lutman Mark E. , Thuroczy Gyorgy , Sliwinska-Kowalska Mariola , Tavarkiladze Georgy , Uloziene Ingrida , Uloza Virgilius , Mishra Shrikanta , Collet Lionel , Ravazzani Paolo
Published: May 2008

To answer concerns as to the potential effects of electromagnetic fields (EMF) generated by third generation mobile phones on the inner ear, the European Commission funded project "EMFNEAR" assessed potential changes in auditory function induced by UMTS field both in humans and in laboratory animals. The purpose of this paper is to present the final outcomes of the project in humans. Normally hearing subjects (18-30 years old) were exposed to 20 min UMTS or sham exposure in a double-blind controlled study. Two different EMF field strengths were used: SAR of 0.069 W/kg using a commercially available phone and SAR of 1.75 W/kg using a patch antenna. Audiological assessment, involving pure tone audiometry, distortion product otoacoustic emissions, effects of contralateral acoustic stimulation on Transiently evoked otoacoustic emissions and late cognitive potentials (P300), were performed before and immediately after real or sham exposures. Results showed no effects of acute UMTS electromagnetic fields exposure on the inner auditory system of humans.
Phase interactions between auditory filter and complex stimuli: psychophysical evidence for level dependence in cochlear phase response
Authors: Shen Yi , Lentz Jennifer
Published: May 2008

Harmonic complexes with the same power spectrum and different phase spectra lead to significant differences in their efficiency in masking pure-tone signals. This process is presumably due to phase interactions between the masker and the cochlea, leading to internally represented waveforms with different amounts of modulation. The present study applied this idea to estimate the phase characteristic of the auditory system at different stimulus levels. Two masking experiments were conducted for estimating whether auditory-filter phase curvatures are level dependent at 2 and 4 kHz. Curvatures were measured at fixed masker levels ranging between 50 and 90 dB SPL in one experiment and at fixed signal levels (25 - 50 dB SPL) in a second experiment. Results from both experiments suggest a level dependence in the auditory-filter phase curvature at both frequencies, which shifts from a negative value towards zero with increasing excitation level. A plausible explanation for this observed level dependence was proposed with the use of a nonlinear cochlear model. This modeling approach indicated that the behaviorally measurable phase curvature is affected by level dependent alterations in the magnitude and phase response of the basilar membrane.
Is auditory intensity discrimination a comparison of entropy changes
Authors: Nizami Iftikhar
Published: May 2008

In JASA (97, 1995), Wong & Norwich presented a Weber-fraction equation derived from McConville, Norwich, & Abel (Int J Biomed Comput 27, 1991). The latter modeled two-alternative forced-choice discrimination between stimuli of identical spectra and identical durations “t” but differing intensities I and I+ΔI. Discrimination depended on ΔH(I,t), the change in the information-theoretic entropy over t and ΔI. ΔH(I,t), assumed constant over intensities, emerged as one of five unknowns in a Weber-fraction equation, (ΔI)/I=f(t0,tW,n,β,ΔH(I,t)). McConville et al. presumed values for n and tW. Using (ΔI)/I≈ΔH(I,t)/(IΔt[∂2H/∂I∂t]) and setting Δt=t, f(t0,tW,n,β,ΔH(I,t)) was approximated as g(n,(β/t),ΔH(I,t)) =ΔH(I,t)/(It[∂2H/∂I∂t]), which was then curvefitted to one listener's Weber fractions. The obtained ΔH(I,t) alone was substituted back into f(t0,tW,n,β,ΔH(I,t)), which was then substantiated by curvefitting to the data to reveal the remaining unknowns, t0 and β. McConville et al. had to curvefit, because they model only a single, unspecified forced-choice trial, making ΔI any intensity change; and none of the unknowns could legitimately be presumed. The curvefitting was flawed: the assumption ΔH(I,t)=constant affirms Fechner's postulate; and ∂2H/∂I∂t<0, giving a negative Weber fraction. McConville et al. fail to explain auditory intensity discrimination as a comparison of entropy changes, casting doubt on Wong & Norwich (1995).
Comodulation masking release and its representation in human auditory cortex
Authors: Ernst Stephan M. , Verhey Jesko , Uppenkamp Stefan
Published: May 2008

The aim of the present study was to find a correlate of the psychoacoustical effect of comodulation masking release (CMR) in human auditory cortex using functional magnetic resonance imaging (fMRI). The target stimulus was a sinusoidal signal embedded in a band limited white noise which was either unmodulated or multiplied with an irregular square-wave modulator with mean modulation frequency of 40 Hz (comodulated condition). For all listeners participating in the fMRI study, the average psychoacoustic threshold difference between the unmodulated and the comodulated condition (i.e., the CMR) was 20 dB. Similar to the results from a previous fMRI study on pure-tone masking (Ernst, Verhey, Uppenkamp, ARO abstracts 30 (2007), p. 302(A)), a spatial dissociation of changes of overall level and signal-to-noise ratio in auditory cortex was found. The comparison of the fMRI activation maps for a signal presented in modulated and in unmodulated noise reveals that those regions in the antero-lateral part of Heschl's gyrus previously shown to represent the audibility of a target (rather than overall level) exhibit a stronger activation for the modulated than for the unmodulated conditions. This result is interpreted as a physiological correlate of the psychoacoustical CMR effect at the level of the auditory cortex.
A filterbank model of human nonlinear auditory frequency selectivity
Authors: Eustaquio-Martín Almudena , Lopez-Poveda Enrique A.
Published: May 2008

Filterbank models of human nonlinear auditory frequency selectivity are useful in a variety of applications. Existing filterbanks are almost certainly flawed because they do not account for the recent observation that compression extends to a wider range of stimulus frequencies in apical than in basal cochlear sites [Lopez-Poveda et al. (2003), J. Acoust. Soc. Am. 113, 951-960]. Here, we present a filterbank based on the forward-masking data from which this observation was made. A forward-masking model was constructed by cascading a linear “outer/middle-ear” filter, followed by a dual-resonance nonlinear (DRNL) filter, followed by a linear temporal window. The temporal window was assumed to be identical across listeners and cochlear places. Only the parameters of the DRNL filter were adjusted to simulate the absolute threshold and the masking data of three listeners for probe frequencies of 0.5, 1, 2, 4, and 8 kHz. A bank of DRNL filters was then constructed by linear or quadratic regression of the optimum parameters. It is discussed that this filterbank is the best possible approximation of human level-dependent auditory frequency selectivity to date. Additionally, the results support the linearity of the temporal window. [Work supported by IMSERSO 131/06, PROFIT CIT-390000-2005-4, MEC BFU-2006-07536.]
Object's width and distance distinguished by the blind using auditory sense while they are walking
Authors: Miura Takahiro , Ueda Kazutaka , Muraoka Teruo , Ino Shuichi , Ifukube Tohru
Published: May 2008

Mobility aid has recently become important for the blind because of increasing their outgoing opportunity. It is necessary for the blind to acquire “obstacle sense” by which they can recognize surrounding objects auditorily. In particular, it is indispensable to investigate the characteristics of the obstacle sense while they are walking. However, training method for the mobility has not been systematically proposed yet because factors regarding the obstacle sense while walking remain unknown. Final goal of this study is to propose a systematic training method for their mobility using the obstacle sense. In this study, the authors particularly focused on a relation of interaural differences between both ears to the ability of the obstacle sense while walking toward the obstacles. In the experiments, the blind subjects were asked to answer when they find the obstacle made of wooden plate with various widths in both conditions of head moving and head fixing. Auditory discrimination ability of the obstacles was measured as a function of the obstacle's width and the distance from the blind subject. From the experimental results, it was found that blind people generally can recognize the obstacles better in the head moving case than the head fixing case.
Assessment of simulation quality of three different auralization procedures
Authors: Paul Stephan
Published: May 2008

When acoustical problems occur in architectural spaces acousticians are often requested to help. The help is often complicated by very different knowledge in acoustics and problems in communication between architect, musicians and acousticians. Auralization of sound sources is considered to be a powerful tool to solve the problem, making acoustic information accessible for hearing. The present research assessed the quality of the output of different simulation procedures by subjective assessment of similarity with a reference sound, considering different perceptual dimensions (localization, reverberation, and timbre). The reference sound was obtained by binaural recording in the room that was auralized using ray-tracing, mirror sources or a hybrid pyramid tracing method. Two different types of sound sources, human speech and a guitar, were auralized. The results show that the subjective quality of the simulation procedure depends on the type of sound source and the perceptive dimension that was assessed. In general the mirror source method performed best for localization of speech, whereas ray-tracing was the preferred method for the guitar sound. Overall mirror sources also outperform the other methods when good localization is required. Independent from the source the hybrid method was considered the best for the reverberation dimension.
Spectral masking release with HiRes120 sound processing in cochlear implant users
Authors: Bestel Julie , Sterkers Olivier , Frachet Bruno , Meyer Bernard , Truy Eric , Boyle Patrick , Lorenzi Christian
Published: May 2008

Current sound processors in cochlear implants show poor frequency resolution compared to normal auditory processes. They smooth spectral gaps within background maskers, thereby preventing implant users from experiencing release from masking (i.e., improved speech identification in maskers showing spectral gaps compared to maskers with continuous spectra). The Advanced Bionics' HiRes120 coding scheme aims to increase the transmission of fine-grain spectral information using a strategy based upon current steering. If HiRes120 improves the precision of spectral coding compared to the standard HiRes strategy, listeners should show improved release from masking for the slowest spectral modulations in a noise masker. This hypothesis is tested in newly implanted adults who alternately use HiRes and HiRes120 sound processing for a period of 10 months. Every two or three months, consonant identification is measured in each implantee in the presence of a stationary speech-shaped noise (SSN) masker at a fixed signal-to-noise ratio yielding 30-40% correct identification with unmodulated noise. The SSN masker is either unmodulated or spectrally modulated to produce periodic, three ERB-wide “spectral gaps” in the noise masker. Masking release scores defined as the change in consonant identification performance in modulated versus unmodulated noise will be presented and discussed.
Consequences of regional accent differences for speech perception studies
Authors: Wright Richard , Souza Pamela , Bor Stephanie , Reed Star
Published: May 2008

Sociophonetic research has demonstrated effects of regional accent on vowels. However, little attention is paid to regional accent in hearing and speech perception studies that use standard vowel stimuli. This poster illustrates the importance of these factors to perception. A library of synthetic vowels from nine different regions of the U.S. (e.g., southern California, upper Midwest) was generated according to published formant values. The vowels were categorized into three groups (near, medium, far) according to Euclidean distance in an F1 by F2 space relative to Pacific Northwest (PNW) vowels. Based on several experimental factors, two vowel pairs representing the high back and low front vowels were chosen as stimuli. The near, medium and far exemplars and PNW exemplars were presented to native PNW listeners in a forced-choice identification task. Dependent variables were identification accuracy and reaction time. Task difficulty was manipulated using background noise level. Results indicate that recognition scores were poorer, and reaction time was longer, for vowels that were spectrally distant from the listener's regional accent. These data suggest that researchers should take into account regional accent in selecting vowel stimuli or generating synthetic vowels for general-use speech perception tests. Supported by NIDCD (DC00033, RO1 DC006014).
Estimation model for the speech-quality dimension “Noisiness.”
Authors: Huo Lu , Wältermann Marcel , Heute Ulrich , Möller Sebastian
Published: May 2008

State-of-the-art assessment method of speech-transmission quality (e.g., PESQ or TOSQA) predict the mean-opinion score (MOS) quite accurately, but cannot provide diagnostic information, which is, however, highly desirable for system developers. In our research project, we aim at the development of an attribute-based speech-quality measure, which provides estimates of different attributes of speech samples and then maps them to one integral-quality estimate. Three dominant, mutually orthogonal perceptual dimensions were firstly identified by auditory experiments and multidimensional analysis (MDA) for narrow-band speech transmission: “directness/ frequency content,” “continuity,” and “noisiness.” The present paper focuses on the further decomposition and measurement of the global dimension “Noisiness.” Therefore, an auditory test including samples degraded by different kinds of noises has been conducted. The subsequent MDA indicates that at least two sub-dimensions (SD), “Speech Contamination” and (perceived) “Additive-Noise Level,” are further describing the global dimension “Noisiness.” The first SD characterizes the degree the noise distorts the speech signal as such, whereas the second SD reflects the degree the additive circuit or background noise itself annoys the listener. The instrumental estimation methods for both SDs and the mapping to the integral-quality ratings are presented in this paper.
Stimulus effects on spectral shape discrimination
Authors: Shrivastav Mini N. , Eddins David A.
Published: May 2008

For a single stimulus such as shaped broadband noise, spectral-shape discrimination can vary based on the nature of the spectral feature that is being detected. For example, Shrivastav et al. (2006) found a significant difference in thresholds for broadband noise with a narrow localized spectral peak and those with a broad overall spectral change. They also found a moderate association between discrimination thresholds and speech-identification scores in older hearing-impaired listeners, but only for the stimuli with a narrow spectral peak. It is not clear whether these stimulus-dependent effects were associated with the bandwidth of the spectral peak, the slope of the peak, or a combination of these features. In the present study, spectral shape discrimination thresholds and speech recognition scores will be measured for ten young normal-hearing and ten older hearing-impaired listeners. The broadband noise will vary systematically in the bandwidth and the slope of a single spectral peak. The results will determine if and how spectral-shape perception changes with the nature of the stimulus paradigm used to measure it. Further, the results will also indicate if the association between spectral shape perception and speech identification is observed for all stimuli or only to a subset.
Across-frequency processes involved in auditory detection of coloration
Authors: Buchholz Jörg M. , Kerketsos Paris
Published: May 2008

When an early wall reflection is added to a direct sound, a spectral modulation is introduced to the signal's power spectrum. This spectral modulation typically produces an auditory sensation of coloration or pitch. Throughout this study, auditory spectral-integration effects involved in coloration detection are investigated. Coloration detection thresholds were therefore measured as a function of reflection delay and stimulus bandwidth. In order to investigate the involved auditory mechanisms, an auditory model was employed that was conceptually similar to the peripheral weighting model [Yost, JASA, 1982, 416-425]. When a “classical” gammatone filterbank was applied within this spectrum-based model, the model largely underestimated human performance at high signal frequencies. However, this limitation could be resolved by employing an auditory filterbank with narrower filters. This novel filterbank was designed to approximate auditory filter-shapes measured by Oxenham and Shera [JARO, 2003, 541-554], derived from forward masking data. The results of the present study demonstrate that a “purely” spectrum-based model approach can successfully describe auditory coloration detection even at high signal frequencies.
Contribution of the tyre to further lowering tyre/road noise
Authors: Saemann Ernst-Ulrich
Published: May 2008

The tyre is the only part of a vehicle that must be originally and primarily designed to transmit forces to outside the vehicle. At the same time the amount of energy a tyre consumes per kilometre in operation and for production has to be minimized. On dry, wet, and snow-covered roads, the safety of traffic can only be ensured by a sufficient capability for acceleration and braking deceleration, cornering stability, tracking on acceleration and braking, steering precision and direction stability. The high requirements on safety, economy, and durability limit the possible reduction in the emission of tyre/road noise. Nevertheless, nowadays patterned tires can be constructed which are not more than 1-3 dB(A) louder than smooth tires. As a further reduction of tire excitation by tread pattern optimization cannot be expected and a soft tread compound cannot be used due to the customer's requirements, the only possibility to build tyres with less sound radiation is to lower the noise already from the blank tyre. Considerably more tyre/road noise reduction can be gained if the excitation by road is addressed, too.
Dependence of the contact area on the velocity of a rolling tire
Authors: Nguyen Hong Hai , Cesbron Julien , Anfosso-Ledee Fabienne , Yin Hai Ping , Erlicher Silvano , Duhamel Denis
Published: May 2008

It is known that the eigenfrequencies of a rolling tire depend on the velocity of rotation. We distinguish two causes for the stiffness increase: the frequency dependence of the complex modulus of the materials and the geometrical stiffness. The real part of the Young's modulus is monotonic according to the frequency. It contributes for an important part to the stiffening. The geometrical stiffness also increases with the rotational velocity. A consequence of these effects is the modification of the size of the contact area for different velocities of a rolling tire. Here we first present experimental results estimating the size of the contact area for a tire in statics and for different rolling velocities. Differences of 20% can be observed. Then the viscoelastic behaviours of the tire materials are presented and experimental results showing the frequency dependence of the complex modulus of the tire constitutive materials are given. Then finite element computations are presented with a real distribution of materials in the tire section and the size of the contact area is estimated and compared to experimental measurements. These results could improve the modelling of tire road interaction for tire noise predictions.
IC engine velocity fields, spherical harmonics and evanescent waves
Authors: Machetta Igor , Nijman Eugenius
Published: May 2008

Spherical nearfield acoustical holography (SNAH) has been used to reconstruct the volume acceleration distribution close to the surface of an IC engine from the measured sound pressure distribution on a sphere enclosing the engine. Such reconstruction frequently requires the calculated target spheres to intercept the strongly nonspherical powertrain structure violating, at first sight, the conventional rules of SNAH. In this paper the SNAH results are compared with the results of two alternative, i.e., an inverse and a power based, source reconstruction methods. Notwithstanding the alleged violation of the rules it is shown that surprisingly good results may be obtained provided the spherical spectrum components associated with evanescent waves are omitted from the back propagation calculation.