bluuebunny/crossref_metadata_2025 huggingface dataset:
Scope of the new standard
Authors: Richings William V.
Published: July 2002

The fundamental requirements for IEC 61672 have not changed. However, practical experience, advances in technology, and current regulations have been taken into account when developing the new standard. The type 0 accuracy category of IEC 651 is almost nonexistent because it is too specialized, while type 3 has been made redundant by the low cost of modern circuitry. Thus the new standard describes only two performance classes corresponding to much improved types 1 and 2 of the previous standard. Important new annexes give detailed procedures for conformance tests and for periodic checks. It is now recognized that the uncertainties of measurement are not negligible and realistic tolerance limits have been specified to include them. Another significant advance for the measurement of impulsive sounds is that a minimum linear operating range of 60 dB is specified for all instruments. Existing and draft European Community Directives call for peak C-weighted measurements and appropriate specifications are given. Requirements for immunity to electrostatic discharges and radio-frequency fields and for radio-frequency emission have been included to cover regulations in Europe and elsewhere. The environmental reference conditions have been changed to 23°C and 50% relative humidity for consistency with the IEC microphone standards.
Tolerances of ‘‘A’’-weighting at extreme frequencies
Authors: Wallis Alan D. , Rice Christopher G.
Published: July 2002

Since IEC 123 (sound level meters) there has been an infinite negative tolerance permitted on the frequency weightings at the extremes of frequency. For example, the attenuation of A-weighting at 31.5 Hz was 39.2 dB, with a tolerance of ±5 dB. At all frequencies below this, the tolerances are +5 dB and minus infinity. A similar situation occurs at 8 kHz and above. Thus a sound level meter which did not respond at all to signals below 31.5 Hz or above 8 kHz may well meet the full requirements of the standard. In 1979, IEC 651 kept the same situation for a type 3 instrument, but changed the frequencies at which infinite negative tolerances were permitted to below 20 Hz and above 12.5 kHz for a type 1 instrument. The August 1998 draft of IEC 61672-3CD also has infinite tolerances but now at 16 Hz and 16 kHz for a class 1 and 20 Hz and 8 kHz for a class 2. Many workers suggest that infinite tolerances should no longer be permitted, while others think that they are essential. This paper evaluates both sides of the argument and offers suggested tolerance figures.
Energy conservation, time-reversal invariance, and reciprocity
Authors: Mohring Willi
Published: July 2002

The scattering of sound waves at a connection of two different ducts is studied. They may carry a mean flow. The two ducts may differ geometrically or in the wall properties, and the transition from one duct to the other may be smooth or abrupt. The wall is assumed to react linearly, but not necessarily locally. An incident acoustic mode generates transmitted and reflected waves. For potential flow and lossless walls, an energy conservation theorem is valid. There is then also usually an invariance with respect to time reversal, which includes reversal of the mean flow. These properties imply reciprocity with reversed flow. Possible generalizations to vortical mean flow are discussed. These relations can be extended to a certain class of absorbing materials which are important in engineering and which show significant losses. This class consists of materials which are obtained from lossless materials by complexifying otherwise real material constants. (A resistance can be understood as an imaginary capacitance.) A reciprocity relation can then be obtained by analytic continuation, although there is neither energy conservation nor time-reversal invariance.
Acoustics of ducted sources in motion
Authors: Myers M. K.
Published: July 2002

The radiation of sound into free space from sources enclosed in short ducts in subsonic forward motion has recently been of intense interest in connection with ducted fan aircraft engine noise technology. The current paper describes a boundary integral approach to calculating such fields which is applicable to arbitrary sources in circular ducts whose inner surfaces are lined with locally reacting absorbers. The theory is developed via a scattering formulation and leads to a system of two coupled singular boundary integral equations. For the case of a rigid inner duct surface, the system reduces to a single equation similar to that of unsteady subsonic lifting airfoil theory. The paper includes a description of the theoretical formulation and of a numerical solution of the governing integral equations. The numerical implementation is extremely economical to achieve, and its accuracy is affirmed by comparison with available results from alternate solutions obtained using CFD methods. Various results are presented to illustrate the effect of important parameters on the characteristics of the radiated sound.
Sound propagation in a conical duct with flow
Authors: Starobinski Rudolf N.
Published: July 2002

The variations of acoustical exergy and acoustical mass velocity are used for a description of three-dimensional sound propagation in quasi one-dimensional moving medium in a conical duct of a different cross-sectional shape. Solution for the sound propagation in this system is represented by the solution for a matched slightly deformed conical waveguide without flow (reciprocity part of the propagation) corrected by nonreciprocity time delay that takes into account convection of the sound by flow. Equivalent circuit for a sound propagation in a conical duct is represented by two successive separate elements: reciprocity one, which describes a sound propagation in the matched waveguide, and a nonreciprocity part represented by the element of nonreciprocity delay. For the particular dependencies of the cross-sectional area against duct axis, the solution for propagating sound is found as two propagated noninteracted advancing and backward waves. The Green’s functions and equivalent circuits for internal and external sound excitations are found as their decomposition by the eigenmodes of the matched waveguide.
An acoustic levitation technique for measuring the rheology of foam near the order–disorder transition
Authors: Holt R. Glynn , Clarke Cory C. , McDaniel J. Gregory
Published: July 2002

Understanding the rheological behavior of foams is important as a basic problem in fluid physics, and as a practical problem in many industries. Foams are tremendously important in a variety of applications. The most important quality of a foam in many of these applications is its response to imposed strain, or its rheological behavior. Yet there exists almost no experimental data on the rheological properties of real 3-D foams. This is due in large part to the earth-based requirements for contact containment, and to the fact that gravity-induced drainage quickly destroys all but the ‘‘driest’’ foams. A unique method to provide noncontact control and manipulation of foam samples, via acoustic levitation, is described. This levitation technique, coupled with low-gravity conditions, will enable investigation of dry (ordered) and wet (disordered) foams. The analysis which will allow determination of a foam’s yield stress, effective bulk modulus, and effective bulk viscosity from the observed response of a foam sample to quasistatic, step function, and periodic acoustic and ambient pressure changes is outlined. Experimental results will be presented for foams experiencing small deformations. The results will be analyzed to determine if the foam may be modeled as a viscoelastic solid. [Work supported by NASA.]
Experimental analysis of the propagation of elastic waves in a chain of spherical beads
Authors: de Billy M. , Jia X.
Published: July 2002

Granular materials are widely encountered in many domains such as soil mechanics, geophysics, and physics of condensed matter. Consequently, these media have been extensively analyzed in recent years [A. N. Bogdanov and A. T. Skvortsov, Sov. Phys. Acoust. 38, 224–226 (1992) and C. Coste et al., Phys. Rev. E 56, 6104–6117 (1997)]. The present experimental study is concerned with the propagation of an elastic wave through a chain of spherical beads submitted to a static force. Two piezoelectric transducers are used for the generation and the detection of the trainwaves. A low-frequency signal is observed in the transmitted acoustic waves along the chain of beads. The central frequency (25<f<200 kHz) of this signal varies with the static force exerted on the beads and also with the diameter (d) of the spherical particles (2<d<8 mm). For a constant value of the static force, the amplitude of the signal is strongly affected by the material of the solid medium which support the acoustic wave (brass, steel, nylon). The increasing of the sound velocity with the applied force seems to verify the prediction based on the Hertzian contact.
Multilayered Rayleigh waves in anisotropic periodically multilayered media: Comparison between theory and experiments using the acousto-optic technique
Authors: Potel Catherine , de Belleval Jean-Francois , Devolder Stefaan , Wevers Martine , Leroy Oswald
Published: July 2002

The propagation of surface waves, particularly Rayleigh waves, has become the subject of a large number of studies. As far as stratified media are concerned, many of the studies deal with an infinite substrate medium below the stratified or nonstratified medium, but, as far as infinite periodically stratified media are concerned, there is no complete work on leaky waves that behave as Rayleigh waves. By analogy with the behavior of the Rayleigh wave in isotropic media, the properties of what this group termed in previous papers ‘‘multilayered Rayleigh wave’’ in infinite anisotropic periodically multilayered media, were studied. These waves are a linear combination of three inhomogeneous Floquet waves and are dispersive. This theory was developed for plane waves. This paper aims to validate this theory by using an experimental acousto-optic technique linked to bounded beams. The experiments were carried out on a composite of carbon/epoxy layers. The coincidence of experimental and calculated dispersion curves of the multilayered Rayleigh modes was found to be quite good. [Work partially supported by the National Fund for Scientific Research and the Flemisch Institute for the Encouragement of the Scientific and Technological Research in Industry. Aerospatiale (France) has provided the characterized sample of carbon/epoxy composite.]
Modal waves in periodically multilayered fluid structures
Authors: Gatignol Philippe , Potel Catherine , de Belleval Jean-Francois
Published: July 2002

This paper aims to study the existence of modal waves and in particular of surface waves, in periodically multilayered fluid media. Generally speaking, these waves are propagation modes for which the acoustical energy propagates along the layers, whereas it remains bounded in a direction perpendicular to the layers. Periodically multilayered media are here studied by the transfer matrix method. The calculus of eigenvalues of the transfer matrix for one period permits to distinguish between passing and stopping regions in the wave number/frequency plane. The transfer matrix for a finite number of periods can be calculated by using Tchebychef polynomials. The writing of the boundary conditions for a finite structure surrounded by vacuum leads to a factorized equation. Thus, two families of guided waves are obtained: the first one corresponds to structure modes which exist in passing regions only. The second one only depends on the period properties and corresponds to inhomogeneous Floquet waves. When the periodic structure is infinite, the modes of this second family coincide with surface waves.
Surface acoustic waves in proton-exchanged lithium niobate and lithium tantalate
Authors: Ciplys Daumantas , Rimeika Romualdas
Published: July 2002

The use of surface acoustic waves in integrated optical devices seems to be very promising for applications in modern telecommunication and data processing technologies. The studies of surface acoustic wave propagation in lithium niobate and lithium tantalate with optical waveguides formed by the proton exchange technique are reported here. The influence of protonated layer parameters on the SAW propagation characteristics is investigated for various crystal cuts and waveguide fabrication conditions. The acoustic velocity and attenuation have been studied by the laser probe method. The effective electromechanical coupling coefficient of the protonated crystal surface has been measured by the method of thin metal film evaporation. Possibilities for controlling both the optical and acoustic properties of proton-exchanged waveguides by the post-exchange annealing have been studied. The results of experimental studies of SAW propagation parameters are compared with those of theoretical calculations performed for a layered structure, and the parameters of a protonated layer are evaluated. The light modulator based on the interaction of surface acoustic wave and guided optical modes is demonstrated.
The precedence effect: Fusion and localization dominance
Authors: Yost William A.
Published: July 2002

Fusion and localization dominance are two aspects of processing sounds in reverberant spaces. If a single sound source is perceived when a source and its reflections are presented then a perceptual fusion of the source and reflection has occurred. Localization dominance refers to the spatial location of a sound source and its reflections being dominated by the location of the source. Four listeners were presented a transient sound from one loudspeaker (source) in a sound-deadened room followed a few milliseconds later by the presentation of the transient at another loudspeaker (reflection). The listeners determined how many sound sources were detected (fusion) and the spatial location of these sources (localization dominance). The results will be discussed in terms of the temporal delay between the source and reflection (0.5 to 64 ms), the number of presentations of the source and reflection (1, 3, 6, 7, 9, 12), and three conditions of switching the source and reflection after the sixth presentation: no switch, the location of the source and the reflection were reversed (reversal switch), and the location of the source and reflection were moved in the same direction (lateral switch). [Work suported by NIDCD and AFOSR.]
The cocktail party effect: Research and applications
Authors: Bronkhorst Adelbert W.
Published: July 2002

The ‘‘cocktail party problem,’’ defined in 1953 by Cherry [J. Acoust. Soc. Am. 25, 975–979 (1953)] as ‘‘how do we recognize what one person is saying when others are speaking at the same time’’ has been the subject of a considerable number of studies in the last 45 years. Whereas Cherry already hypothesized that there are multiple effects that contribute to the ability to extract one speaker out of a babble, the term ‘‘cocktail party effect’’ has been claimed by only one of them: the influence of spatial separation of the voices. One important conclusion from past research on the cocktail party effect is that the truly binaural gain (the ‘‘unmasking’’) is, in general, relatively small (2–4 dB). The additional ‘‘acoustic’’ gain due to head shadow effects may be larger but depends strongly on the circumstances. In the present paper the research will be reviewed including recent evidence that much larger binaural gains may occur when the masker is ‘‘informational’’ in nature [Kidd et al., J. Acoust. Soc. Am. 104, 422–431 (1998)]. In addition, several applications based on the cocktail party effect, such as the use of a virtual auditory display for multiple-speaker communication, will be highlighted.
Evaluation of PEMO in robust speech recognition
Authors: Kasper Klaus , Reininger Herbert
Published: July 2002

A major problem in speech recognition is the robustness of recognition performance against additive background noise and convolutive distortions due to changing transmission channels or varying microphone characteristics. One approach to overcome this problem is to apply PEMO [Dau, Püschel, and Kohlrausch, J. Acoust. Soc. Am. 99, 3615–3622 (1996)] for extraction of noise robust feature vectors. The recognition performance achievable with PEMO in combination with a locally recurrent neural network (LRNN) or hidden Markov models (HMM) for feature scoring was evaluated in a task of speaker-independent word recognition. The robustness was tested and compared with that of other feature types by applying the speech recognition systems to speech signals disturbed by additive background noise and to speech signals recorded over telephone lines. It was found that only with LRNN it is possible to exploit the potential of PEMO, not with HMM. A detailed analysis of the interplay between PEMO features and the scoring techniques revealed that the long-term dependencies in the sequence PEMO features can only be captured by LRNN. Furthermore, LRNN discriminate between the distinct and sparse peaks of the PEMO speech representation—which are well maintained also in the case of noisy speech—and artifacts introduced by the additive or convolutive noise.
Models of frication: Advances and limitations
Authors: Shadle Christine H.
Published: July 2002

The increasing number of modeling studies of fricatives and frication in recent years is due at least partly to two major advances: increasing computational power makes it feasible to simulate the flow, and thus construct a more physically accurate model; improvements in vocal-tract imaging, particularly magnetic resonance imaging (MRI), allow capture of three-dimensional vocal-tract shape data, especially including small constrictions formed by soft tissue. However, the complexity of both techniques still tends to lead to incomplete models of frication, limited to static and/or highly simplified tract shapes. Further, the three-dimensional data are often used only to generate an area function, ignoring the cross-sectional shape data that can be crucial in defining aeroacoustic sources. Fricatives are not static, and some of their dynamic behavior, such as apparent modulation of the noise source in voiced fricatives, may be especially ill-served by quasistatic models. Dynamic MRI techniques can be used to acquire shape data with which to pursue dynamic models. Finally, the program VOAC will be discussed briefly (and in more detail elsewhere in this session) as an example of a way to use three-dimensional data and acoustic-flow interactions to enhance the model without unduly increasing computational, or conceptual, complexity.
A computational study of glottal obliquity
Authors: Scherer Ronald C. , De Witt Kenneth J. , Afjeh Abdollah A. , Zhang Chao , Frankel Steven H.
Published: July 2002

Glottal motion is not always symmetric during phonation. The cycle phase of one vocal fold may differ from that of the other, creating a dynamic glottal center line oblique to the tracheal center line. This condition is called ‘‘obliquity’’ of the glottis. Intraglottal pressures for a range of obliquity angles were obtained using a finite difference computational technique for steady flow in static geometries. As an example, for a uniform glottal duct, obliquity of 20 deg (one side convergent, the other divergent), subglottal pressure of 7.8 cm H2O, and glottal diameter of 0.032 cm: (1) air pressures were significantly different between the two glottal walls (as large as approximately 24 pressures measured perpendicular to the tracheal axis, but less if measured perpendicular to the glottal duct, (2) pressure values were different in amount and even polarity from that expected for a uniform glottis with zero obliquity, and (3) there were significant pressure differences at glottal exit between the two sides. Aerodynamic equations for glottal flow need to be modified to account for obliquity. The computational pressure profiles will be compared to empirical results using a Plexiglas model (M5) of the larynx. [Work supported by NIH grant 1R01DC03577-01A1.]
A model of vocal-tract acoustics and aeroacoustics validated by flow experiments
Authors: Jackson Philip J. B. , Shadle Christine H.
Published: July 2002

Modeling the acoustic response of the vocal tract is a complex task, both from the point of view of acquiring details of its internal geometry and of accounting for the acoustic-flow interactions. A vocal-tract acoustics program (VOAC) has been developed [P. Davies, R. McGowan, and C. Shadle, in Vocal Fold Physics, edited by I. Titze (Singular, San Diego, 1993), pp. 93–142], which uses a more realistic, aeroacoustic model of the vocal tract than classic electrical-analog representations. It accommodates area and hydraulic radius profiles, smooth and abrupt area changes, incorporating end corrections, side branches, and net fluid flows, including turbulence losses incurred through jet formation. Originally, VOAC was tested by comparing vowel formant frequencies (i) uttered by subjects, (ii) predicted using classic electrical analog, and (iii) predicted by VOAC. In this study, VOAC is further validated by comparing the predicted frequency response functions for a range of flow rates with measurements of the radiated sound from a series of mechanical models of unvoiced fricatives [C. Shadle, Ph.D. thesis, MIT-RLE Tech. Report 506 (1985)]. Results show VOAC is more accurate in predicting the complete spectrum at a range of flow rates. Finally, preliminary work is presented with VOAC used to simulate the sound generated at a sequence of stages during the release of a plosive.
The effects of source characteristics on the auditory localization of nearby sources
Authors: Brungart Douglas S. , Durlach Nathaniel I.
Published: July 2002

A series of recent experiments has examined the auditory localization of a nearby (<1 m) sound source under four conditions: (1) a fixed-amplitude condition where loudness-based distance cues were available; (2) a monaural condition where the contralateral ear was occluded by an ear-plug and muff; (3) a high-pass condition where the stimulus bandwidth was 3 Hz–15 kHz; (4) a low-pass condition where the stimulus bandwidth was 200 Hz–3 kHz. The results of these experiments were compared to those of a previous experiment that measured localization performance for a nearby broadband, random-amplitude source [Brungart et al., J. Acoust. Soc. Am. 102, 3140(A) (1997)]. Directional localization performance in each condition was consistent with the results of previous far-field localization experiments. Distance localization accuracy improved slightly in the fixed-amplitude condition, especially near the median plane, but was severely degraded in the monaural condition. Distance accuracy was also found to be highly dependent on the low-frequency energy of the stimulus: in the low-pass condition, distance accuracy was similar to that in the broadband condition, while in the high-pass condition, distance accuracy was significantly reduced. The results suggest that low-frequency interaural intensity differences are the dominant auditory distance cue in the near-field.
Sound-image broadening by a single echo and its relation to the transient interaural cross-correlation function
Authors: Yanagawa Hirofumi , Okuno Takatoshi
Published: July 2002

The sounds reproduced by two loudspeakers often consist of a preceding sound and its echo when the listener’s position is offset like the position of a driver when listening to a car stereo. Consequently, the sound image is broadened by the echo. In this article, the width of the sound image produced by the preceding sound and the echo under a loudness balance condition were examined. TRICC (the maximum value of the transient interaural cross-correlation function) was then applied to analyze such sound image broadening. In hearing experiments, a pair of noise bursts was used as a model of transient sound, such as speeches and musical sounds. A pointer noise (a pair of noises with correlation coefficients) was used to express the width of the sound image. The experiments showed that the width of the sound image increases as delay time between the preceding sound and the echo increases. When the delay time becomes longer than 10 ms, the width of the sound image corresponds to the value of the interaural correlation coefficients and not to the value of TRICC or IACC.
Modeling scattering by objects near an interface
Authors: Fawcett John A.
Published: July 2002

For an object totally above or below an interface, the overall scattering from the object and the interface can be modeled as a series of multiple interactions [e.g., Hackman and Sammelmann, J. Acoust. Soc. Am. 84, 1813–1825 (1988)]. The theory is outlined for a spherical or infinite cylindrical shell and the effects of the sediment sound speed and the source/receiver geometry on the backscattered time series are numerically investigated. The case of an object in a rough or range-dependent waveguide is also considered. Partial burial of an object is discussed. Some comparisons of modeled and experimental data (both in the spectral and temporal domains) are presented.
Analysis of boundaries’ effects in the evaluation of transient ultrasonic fields scattered by a rigid reflector
Authors: Hassina Khelladi , Hakim Djelouah
Published: July 2002

One approach used to estimate the transient field scattered by a target with a known dimension and geometry is the convolution method. In the hypothesis of linear acoustic, and for a perfectly rigid reflector immersed in an isotropic, homogeneous, and lossless fluid, the detected acoustic pressure is expressed in the form of a time convolution between the radiator velocity profile and the transmit-receive impulse response. This last depends on the geometry of the transducer, the target, their relative position, and physical characteristics of the propagation medium. For that purpose, some simulations were done. The pressure waveform is explained in terms of the plane and edge waves. In order to determine the boundaries’ effects on the detected pressure, targets of different size were used. The obtained results show that the edge waves were insignificant when large size targets are used.
On subjective impact sound insulation classes
Authors: Hammer Per , Nilsson Erling
Published: July 2002

The possibility to divide impact sound annoyance into classes is investigated. The experiments, based on human perception, are done in a laboratory environment where various floor structures have been included to produce impact noise. These tests are correlated to studies pertained to real-life situations for tenants. The statistical tool to test the significant differences between the classes is Rou–Kupper. Real footsteps are used as a noise source. In addition, airborne sound insulation is treated in a similar manner, whereby one may conclude that there are some difficulties finding classes with statistical significant differences. [Work supported by the Swedish Council of Building Research.]
Ultra-wide bandwidth backscattering measurements using a transparent flat PVDF sheet source
Authors: Morse Scot F. , Gipson Karen , Kaduchak Greg , Williams Kevin L. , Hefner Brian T. , Marston Philip L.
Published: July 2002

A thin extended flat PVDF film surrounded by water is demonstrated to be suitable for exploring scattering responses of complicated targets over a range of frequencies from below 2 kHz to 1000 kHz. The target lies close to the source, and in the configuration normally used, the scattering passes through the source to a distant hydrophone. While initial experiments [Kaduchak et al., J. Acoust. Soc. Am. 97, 2644–2708 (1995)] explored the resonances of spherical shells for which analytical solutions are known, recent experiments have explored novel features in the responses of truncated tilted cylinders that are either hollow [Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)] or solid [K. Gipson, Ph.D. thesis, Washington State Univ. (1998)]. The spectrum radiated by the sheet can be altered by using voltage-step, voltage-pulse, or weighted chirp excitations. An equivalent circuit model is useful for describing the radiated spectrum. Crisp tone bursts have also been produced and used to study the low-frequency resonances of a steel shell in Lake Union (Seattle). [Work supported in part by the Office of Naval Research and by APL.]
Mechanical properties of lead magnesium niobate/lead titanate ceramics
Authors: McLaughlin Elizabeth A. , Ewart Lynn
Published: July 2002

This research examines the mechanical properties of doped electro- strictive lead magnesium niobate / lead titanate (PMN-PT). While optimization of the electromechanical properties has been the focus of the materials development effort, mounting anecdotal evidence indicates that there are problems with the mechanical integrity of PMN-PT. Mechanical testing has been employed (1) to measure the flexural strength of doped PMN-PT and understand the causes of failure, and (2) to measure the compression strength of PMN-PT and identify the onset of microstructural damage. Navy type-III ceramic (PZT8) was measured as a benchmark. The average flexural strength of poled PZT8 was found to be 110 MPa. Average flexural strengths ranging from 44 to 60 MPa were measured for batches of barium- and lanthanum-doped PMN-PT. Fractography identified the causes of failure. Process modifications, by one vendor, have increased the flexural strength by 38%. The average compression strength of unpoled PZT8 was found to be 1040 MPa. An average compressive strength of 890 MPa was measured for barium-doped PMN-PT. Prior to failure, a ceramic develops microstructural damage at levels below the compression strength. Evidence of damage was found at stresses as low as one-third of the compressive strength. [Work supported by ONR and SPAWAR.]
Psychoacoustic model for calculating the sound quality of piano tones
Authors: Valenzuela Miriam N.
Published: July 2002

Assuming that only audible dissimilarities between different piano tones may lead to different quality judgments, experiments were conducted to determine the perceptual attributes listeners use to judge these dissimilarities. The psychoacoustic results showed that two major attributes contribute with over 90% to the explanation of the perceived dissimilarities: the psychoacoustic ‘‘sharpness’’ and a second attribute that was described with the scale ‘‘open–closed.’’ Both attributes depend on the specific loudness distribution of the sound signals and are defined as a weighted first moment of the critical-band rate distribution of specific loudness using different weighting functions. The weighting function used to calculate the second attribute emphasizes spectral components around 1 kHz. The model developed for calculating audible dissimilarities between piano tones showed a good agreement between psychoacoustically measured and calculated dissimilarities; the correlation was 0.90. The influence of the two attributes on sound quality judgments was verified by listening tests with appropriately modified piano sounds. The results showed that calculating the sound quality of musical instruments on the basis of their sound signals requires an aurally adequate signal processing. The model developed to calculate the sound quality of piano tones showed a good agreement between measured and calculated quality orders.
Analysis of the excess noise of aircraft pusher propellers
Authors: Schulten Johan B. H. M.
Published: July 2002

A pusher propeller configuration offers several advantages over the traditional tractor arrangement. For instance, the wing of a twin-engined aircraft is no longer exposed to the swirling and turbulent slipstream. This results in a much smoother wing inflow, a prerequisite for aerodynamic refinement. Acoustically, the more aft position of the propellers considerably reduces the noise impact on the fuselage, yielding the potential of a low cabin noise level. However, in general, the exterior noise of pusher propellers is augmented by the interaction with impinging wakes and exhaust jets. The present paper addresses the physical mechanism of this interaction by applying an unsteady lifting surface theory to the propeller blades. This requires the incident field to be resolved in circumferentially harmonic Fourier components. For each component the unsteady blade pressure distribution is computed as source input for an acoustic calculation. From sample computations for typical operating conditions it appears that the interaction substantially contributes to the total radiated noise of pusher propellers. The present method offers the possibility to investigate in detail the effect of alterations in blade design and flight conditions on tonal level and directivity.
Active noise control by use of an aeroacoustic instability
Authors: Lange Björn , Ronneberger Dirk
Published: July 2002

Ducts that are lined with a series of equally spaced cavities exhibit strong amplification of sound waves under specific flow conditions. The amplification is caused by an aeroacoustic instability wave traveling in the boundary layer of the lining. Since the effect is coupled with a drastic variation of the static pressure drop that depends on the amplitude of incident sound, the possibility is implied to efficiently generate high intensity sound at low frequencies: An incident sound wave with harmonically varying amplitude will cause a periodic modulation of the pressure drop and thus lead to the generation of sound at the modulation frequency. Based on these observations, an aeroacoustic loudspeaker has been designed combining a lined duct section as part of a flow channel and a conventional loudspeaker. The output power of the device amounts to up to 95 dB re: 1 pW/Hz at Ma=0.25 for frequencies ranging between 0 and 200 Hz—an observation of some significance with regard to the fact that traditional loudspeakers tend to be rather inefficient at low frequencies. As a feasibility test, the aeroacoustic loudspeaker is used as an actuator in an active noise control setup. High attenuation of low-frequency noise is achieved.
The influence of sound quality on expected visual impression
Authors: Söderholm Monica M. , Västfjäll Daniel
Published: July 2002

Information from visual and auditory systems is often linked. One example of the cross-modal connection between sound and visual experience is different materials that easily can be identified by their sound quality. The purpose of this investigation was to analyze the anticipated visual impression of three vacuum cleaners when listening to the product. The participants in the listening test where asked to describe the visual impression of the vacuum cleaners and also how they thought the vacuum cleaner sounded like with own words. The 24 listeners were both female and male of different ages and the vacuum cleaners were judged live. Often something that is large, for instance, a truck compared to a car, does produce more sound. The experience that large products are louder than small products is an influence when listening to vacuum cleaners. The listeners expected a large vacuum cleaner when listening to a rather loud vacuum cleaner. There was a unanimous opinion among the participants that a loud vacuum cleaner was ugly, had a box shape, and was old. The vacuum cleaners that were described to have a nice sound were described as small and round with a nice design and nice colors.
About perceptivity of narrow-band frequency response variations of loudspeakers
Authors: Krump Gerhard
Published: July 2002

Many loudspeakers show peaks and gaps at 1 kHz caused by the connection of the hard cone and soft surround, which produces interferences and complex vibrational modes. Great efforts are made by the speaker manufacturer to avoid this by changing the surround geometry and material, whereas primarily knowledge about the perceptive limits of the peaks and gaps in frequency response would be necessary. For this investigation line spectra with equal amplitudes and statistical phases between 1 Hz and 20 kHz were calculated by a personal computer. At 1 kHz spectral enhancements or gaps with a bandwidth of 1 Hz or of a half, one, or two critical bands were realized with five different critical band levels. Ten test persons had to compare the first line spectrum with equal amplitudes (anchor) with the second signal with spectral changes in a yes–no procedure presented by an earphone with free-field equalizer at a SPL of 70 dB. The just-noticeable changes in spectral envelope are different for enhancements and gaps and depend on the bandwidth and the critical band level of the variations. They can be explained with calculated masking patterns and literature data.
Torsional waves in a viscoelastic layer
Authors: Li Qingchun , Jarzynski Jacek
Published: July 2002

The objectives of this study are first to examine experimentally the propagation of torsional waves in a viscoelastic material, and second to use these data to determine the complex shear modulus of the material. The viscoelastic material used in this study is neoprene rubber. A magnetic drive is used to generate a transient, one-cycle, torsional wave in a brass rod, and this wave is transmitted into a layer of neoprene rubber bonded to the rod. A fiber-optic laser Doppler vibrometer is used as a noncontact probe to measure the torsional wave transmitted through the neoprene layer. The experimental data are compared with predictions from a theoretical model [D. P. Thomas, Int. J. Eng. Sci. 6, 565–570 (1968)]. Also, the complex shear modulus is determined from a least-square fit of the theoretical model to the experimental data using the downhill Simplex method. Another application of torsional waves is to nondestructive testing of materials, particularly for testing the strength of adhesive bonds between layers. [Work supported by ONR.]
Estimates of dynamic strain and stress in pipes by measured average vibration velocity
Authors: Finnveden Svante , Pinnington Roger
Published: July 2002

A velocity method for estimating dynamic strain and stress in pipe structures is investigated. With this method predicted or measured spatial average vibration velocity and theoretically derived strain factors are used to estimate maximum strain. The nondimensional strain factor is defined as the maximum strain times the ratio of the sound velocity to the spatial rms vibration velocity. Measurements are made confirming that this is a descriptive number. Using a spectral finite-element method, numerical experiments are made varying the pipe parameters and considering all 16 possible homogeneous boundary conditions. While indicating possible limitations of the method when equipment is mounted on pipes, the experiments verify the theoretical results. The velocity method may become useful in engineering practice for assessments of fatigue life.
On the dynamic interaction of a pipe conveying fluid with an elastic resisting medium
Authors: Dzhupanov Ventzeslav A. , Djondjorov Peter A. , Vassilev Vassil M.
Published: July 2002

The problem of the dynamic stability of pipes conveying high-speed fluid and lying on an elastic foundation has been a subject of significant interest during the past 30 years due to the broad application of pipes as structural components in different technologies. The present study contributes to the solution of this problem, suggesting a new model of the foundation—an infinitely deep elastic stratum, whose width is equal to the length of the attached pipe. The material of the foundation is supposed to be a homogeneous and isotropic one. Its dynamic behavior is considered in the context of linear elasticity. The pipe vibration is governed by the usual Bernoulli–Navier–Mohr theory. An approximate solution of the respective mathematical problem is obtained applying Galerkin’s method. As a result, the influence of the medium physical characteristics to the flutter dynamic stability of cantilevered pipes through the pair of acoustic velocities is examined.
Application of a roughness model to pathological voices
Authors: Reuter Robert , Herzel Hanspeter
Published: July 2002

Irregularities in voiced speech are often related to the intrinsic nonlinearities in the vibrations of the vocal folds. Desynchronization of vibratory modes can induce nonlinear phenomena such as subharmonics, biphonation (two independent pitches), and deterministic chaos. The resulting complex signals exhibit various amplitude and frequency modulations and are, therefore, perceived typically as rough voices. In clinical studies of pathological voices perceptive roughness scores are widely used. So far, however, no satisfactory correlation of ratings of roughness and acoustic parameters has been found. In this presentation a modified Aures model for the quantification of roughness is introduced. It is exemplified that subharmonics lead to high roughness scores whereas the roughness of biphonation depends strongly on the two frequencies. Finally, a set of 120 perceptually evaluated pathological voices is studied. It turns out that the roughness score obtained from the psychoacoustic model is stronger correlated to the ratings of phoniatricians than conventional perturbation measures such as jitter and shimmer.
Entropy rate based speech segmentation
Authors: Wokurek Wolfgang
Published: July 2002

The sequence of estimates of the speech signal’s entropy rate is investigated as a potential basis for speech segmentation. Raising and falling edges of that entropy rate curve and its maxima and minima are considered as candidates for segment boundaries. These prominent points are compared to the phonetic segment boundaries and to acoustic landmarks [S. A. Liu, J. Acoust. Soc. Am. 100, 3417–3430 (1996)]. The comparison is made using the ‘‘Kiel corpus of read speech’’ which is a phonetically manually labeled corpus of German utterances. The evaluation considers the entropy rate labels against the background of the phone segments. In particular the position and the count of the entropy rate labels within each phone are appraised. The average results are reported both as totals and broken down into phone classes and phones. The frame duration of the entropy rate estimation controls the smoothness of the curve and hence the label count per phone. A similar evaluation relates the entropy rate labels to the acoustic landmarks.
Comparison of wideband LMS, subband LMS, and a nonlinear entropic neural approach to adaptive noise cancellation for speech enhancement
Authors: Shields P. W. , Girolami M. , Campbell D. R.
Published: July 2002

An empirical comparison of three adaptive algorithms for speech enhancement in noisy reverberant conditions is presented. The subband least mean square (LMS) [E. Toner and D. R. Campbell, Speech Commun. 12, 253–259 (1993)] and minimum entropy noise reduction schemes [M. Girolami, Electron. Lett. 33(17), 1437–1438 (1997)] are compared with a reference wideband LMS approach [S. D. Stearns and R. A. David, Signal Processing Algorithms (Prentice–Hall, Englewood Cliffs, NJ, 1988)]. All three methods were applied to the enhancement of speech corrupted with speech-shaped noise. The schemes were tested using simulated anechoic and real-room reverberant (T60=0.3 s) environments. The anechoic and real-room recordings were binaural including head shadow and diffraction effects. The subband LMS adaptive processing scheme uses the LMS adaptive noise cancellation algorithm in frequency-limited subbands. The inputs from each microphone are split into 16 contiguous subbands using a cochlear distribution according the function provided by Greenwood [J. Acoust. Soc. Am. 87, 2592–2605 (1990)]. Each frequency-limited subband is processed using a LMS adaptive noise cancellation filter operating in an intermittent or continuous mode depending on input signal characteristics. The neural network approach is motivated by temporally sensitive hebbian super-synapses, which may form sparse representations based on commonly occurring spatio-temporal input patterns. The results for real-room signals demonstrate statistically equivalent performance of the subband LMS and wideband neural method, both of which prove superior to the wideband LMS algorithm.
Localization in acoustic propagation in water with air cylinders
Authors: Ye Zhen , Hoskinson Emile
Published: July 2002

Wave localization is the peculiar property of a scattering medium that completely blocks propagation, thus inducing a surprising phase transition, for example in optical or acoustic transparency or electrical conductivity. When localized, waves remain confined in space until dissipated. This property has been explained for randomly disordered scatterers. It is generally believed that disorder is an essential ingredient of localization, and in two dimensions (2D) waves are always localized with any amount of randomness. Here it is shown that waves are not always localized in 2D, but under proper conditions even periodic structures can achieve localization in the case of acoustic propagation through water containing an array of air cylinders. An essential component of localization in this case arises from the natural resonance and an amazing collective behavior of the cylinders. Exact numerical calculations reveal the unexpected result that localization is relatively independent of the precise location or organization of the scatterers. The results provide insight on 2D wave localization and offer an opportunity for further investigation of important questions about localization phenomena. [Work supported by NSC and NCU of ROC.]
Considerations for including surface scattering in room-acoustics auralization
Authors: Torres Rendell R. , Kleiner Mendel
Published: July 2002

Recent research in auralization has centered on including wave-theoretical aspects that are unaccounted for by well-developed but frequency-limited geometrical models [Dalenbäck et al., J. Audio Eng. Soc. 42(10) (1994)]. For example, inclusion of edge diffraction (or edge scattering) has been shown (via scale-model measurements and listening tests) to contribute audibly to the early part of the room impulse response [Torres and Kleiner, Proc. 16th Intl. Congress on Acoust. (1998)]. Modeling room surface scattering requires consideration of at least two main concerns: (1) characteristics of typical room surfaces and (2) types of numerical models most suitable for reasonable speed and accuracy. Typical room surfaces (e.g., in concert halls) can have a periodic nature at one wave number-scale and a statistical nature at another. This suggests use of a multiscale, multiple-scattering description possibly based on a combination of perturbation models, ‘‘boss’’ models, variational models, or higher-order Kirchhoff theory. It may also require simplified surface-descriptors like those used for random rough surfaces. The second main concern influences the form of the model (e.g., time-domain versus frequency-domain formulations, chosen surface parameters) and its usefulness for auralization programs. Possible models are discussed with their respective applicability to room acoustics auralization. [Work supported by Johnsons Stiftelse and Teknikbrostiftelsen.]
Intercomparison test of sound insulation measurement in test facilities. II
Authors: Meier A. , Schmitz A. , Raabe G.
Published: July 2002

In the second part of this paper, the results obtained in the principal test are presented and the differences between the sound insulation found in the individual testing facilities discussed. It is moreover shown, if the total loss factor allows the sound reduction indices to be converted, thus a uniform assessment of heavy, solid building elements on all test facilities is achieved. On the basis of these results it will be investigated whether the theoretical approaches of the prediction methods (e.g., ISO 12354) are sufficient for the conversion of the sound insulation of building elements.