bluuebunny/crossref_metadata_2025 huggingface dataset:
A chain matrix model for an acoustically coupled, lead zirconate titanate core, electrical transformer
Authors: Kraszewski Raymond J. , Sigelmann Rubens A. , Herbertz Joachim , Lee Mark
Published: October 2005

Chain matrices are used to generate a functional description of the electrical impedance parameters of a device comprised of three layers of piezoelectric rings and implemented as a two port network. It is shown that this device can be used as a piezoelectric core, acoustically coupled electrical transformer (PT). A circuit representation of the PT is derived and comparisons are made between it and the magnetic transformer (MT). The impedance parameters of a PT, made from three lead zirconate titanate rings, were measured and compared with their corresponding theoretical values. While the approach predicts, in this case, the center frequency of the device with an error of 4.5%, it provides a highly accurate description of its qualitative behavior. The error in the center frequency is attributed to the presence of coupled modes that are ignored by the model. In particular, the tested device did not strictly satisfy the thinness constraints that are imposed by the approximations used. Power transfer calculations predict an efficiency around the resonance frequency in excess of 0.90 for loads ranging from 0.1 to 13 kΩ.
Electrical multiport transfer functions and efficiency in layered media of piezoelectric and/or nonpiezoelectric materials
Authors: Kraszewski Raymond J. , Sigelmann Rubens A. , Herbertz Joachim
Published: October 2005

Electrical impedance parameters of a layered structure tapped at its interfaces and composed of piezoelectric and/or nonpiezoelectric strata are determined using the chain matrix approach. The method, within certain constraints, is applicable, whether the layers are disks, rings, or plates since the constraints ensure that each stratum behaves, to an approximation of negligible error, as a thickness vibrator. The most general case requires that the transverse dimensions of each layer be large in comparison to its thickness, insuring that the acoustical propagating modes are predominantly dilatational. The method is accurate for layers that are composed of uniaxially poled ceramics or when certain electrode geometries are used, since for these cases the dilatational modes are respectively uncoupled or very weakly coupled. Transducers and the acoustically coupled, piezoelectric core electrical transformer, or PT, are some of the devices that can be implemented from structures of layered media so that power and efficiency considerations are addressed within the context of multiple port networks.
Impulse-response method to predict echo-responses from targets of complex geometry. Part I: Theory
Authors: Lhémery Alain
Published: October 2005

A theoretical model is proposed for the complete solution of the acoustical problem of the radiation of transient ultrasonic pulses, their scattering by targets of arbitrary shape and acoustic impedance and their reception. The model combines Kirchhoff’s retarded potential formula with the impulse-response approach to the field radiated into fluids by wideband pistonlike sources. Kirchhoff’s formula is made explicit with three geometrical assumptions. Further assumptions and stated approximations allow a generalization of the reciprocity principle from its already-known form for point targets. This leads to a formula for the complete acoustical impulse response which is explicit, very compact and easy to compute, requiring integration only over the insonified area of the target. Throughout, particular attention is given to the hypotheses and approximations made in deriving the model with clear definition of its domain of applicability.
Active control of noise transmission through a panel into a cavity. II: Experimental study
Authors: Pan Jie , Hansen Colin H.
Published: October 2005

The active control of the noise transmission through a panel into a cavity was investigated experimentally. A sound field generated by external loudspeakers was transmitted into a cavity through a simply supported panel. To control the sound transmission, an electromagnetic driver was used to adjust the panel vibration, so that the sound pressure sensed by a microphone in the cavity was minimized. Distributions of the sound pressure in the cavity and the panel vibration were measured and analyzed under controlled and uncontrolled conditions. Two different control mechanisms were identified and were associated with different types of acoustical mode. For a cavity-controlled mode, which had its resonance frequency close to an uncoupled cavity mode, the panel response increased for the controlled case even though the sound pressure in the cavity was reduced. However, for a panel-controlled mode, where the interior sound field was generated by the radiation of a resonant panel mode, the panel response was suppressed for the controlled case. These results qualitatively verify the previous analytical results [J. Pan et al., J. Acoust. Soc. Am. 87, 2098–2108 (1990)].
Rotation of ultrasonically levitated glycerol drops
Authors: Biswas A. , Leung E. W. , Trinh E. H.
Published: October 2005

Ultrasonic levitation is used to suspend single millimeter-size glycerol drops in a rectangular chamber. Audio-frequency laterally standing waves set up in the chamber are used to torque the suspended drops. The shape evolution of the drop under the combined effect of centrifugal forces and the acoustic radiation stress, along with its angular velocity are monitored, using video imaging and light scattering techniques. The results show good qualitative agreement with the theoretically predicted shape evolution as a function of angular velocity.
Acoustic microcavitation: Enhancement and applications
Authors: Madanshetty Sameer I. , Apfel Robert E.
Published: October 2005

Experimental investigation into acoustic microcavitation is extended to include ‘‘cavitation activity’’ in addition to the threshold measurements using acoustic detectors. The primary setup incorporates two detectors: an unfocused, untuned 1-MHz transducer, which serves as a passive detector, and a focused 30-MHz transducer used in pulse-echo mode as the active detector. Cavitation itself is brought about by a focused piezoelectric transducer driven in pulse mode. The active detector is arranged confocally with respect to the cavitation transducer. Both the interrogating pulse and the cavitation pulse arrive simultaneously at the common focus which is the region of cavitation. Cavitation is conducted primarily at 0.75 MHz and 1% duty cycle in clean water using microparticles to seed the events. Cavitation activity appears to be directly proportional to the number density of the particles present in the cavitation medium. The fact that the active detector affects the cavitation process can be further exploited to seek interesting applications leading possibly to submicronic particle counting and testing of surface characteristics of silica particles used in liquid chromatography.
A datalogger to identify vocalizing dolphins
Authors: Tyack Peter L. , Recchia Cheri A.
Published: October 2005

A datalogger was developed to identify vocalizing dolphins within socially interacting captive groups. Every 50 ms the logger stores data on the level and frequency of detected sound. Dataloggers are temporarily attached to dolphins by suction cups for data collection sessions lasting up to 45 min. Later, computer analysis of data from the dataloggers reveals which dolphin produced each vocalization recorded during the session. Results from use of dataloggers with two captive bottlenose dolphins (Tursiops truncatus) at the New England Aquarium in Boston, MA are presented. The possible use of dataloggers with wild dolphins is discussed.
An investigation of locus equations as a source of relational invariance for stop place categorization
Authors: Sussman Harvey M. , McCaffrey Helen A. , Matthews Sandra A.
Published: October 2005

Locus equations were investigated as a potential metric capable of illustrating relational invariance for place of articulation in voiced initial stop consonants independently of vowel context. Locus equations are straight line regression fits to data points formed by plotting onsets of F2 transitions along the y axis and their corresponding midvowel nuclei along the x axis. Twenty subjects, 10 male and 10 female, produced /b/v/t/, /d/v/t/, and /g/v/t/ tokens for ten vowel contexts. Each CVC token was repeated in a carrier phrase five times yielding 50 tokens per stop place category. Formant measures were obtained using the MacSpeech Lab II speech analysis system. Extremely linear regression functions were found characterized by distinct slopes and y intercepts as a function of place of articulation. A discriminant analysis using F2onset and vowel frequencies as predictors showed 82%, 78%, and 67% classification rates for labial, alveolar, and velar place. Using derived slope and y-intercept values as predictors led to 100% classification into stop place categories. A neurobiologically oriented perspective on the invariance issue is developed and a brain-based recognition algorithm for stop place integrating burst and F2 trajectory cues is offered.
Elastic models of vocal fold tissues
Authors: Alipour-Haghighi Fariborz , Titze Ingo R.
Published: October 2005

Elastic properties of canine vocal fold tissue (muscle and mucosa) were obtained through a series of experiments conducted in vitro and were modeled mathematically. The elastic properties play a significant role in quantitative analysis of vocal fold vibrations and theory of pitch control. Samples of vocalis muscle and mucosa were dissected and prepared from dog larynges a few minutes premortem and kept in a Krebs solution at a temperature of 37±1 °C and a pH of 7.4±0.05. Samples of muscle tissue and mucosa were stretched and released in a slow, sinusoidal fashion. Force and displacement of the samples were measured with a dual-servo system (ergometer). After digitization, stress–strain data for samples of muscle tissue and cover tissue were averaged. The stress–strain data were then fitted numerically by polynomial and exponential models.
Free-field release from masking
Authors: Saberi Kourosh , Dostal Lynda , Sadralodabai Toktam , Bull Vicki , Perrott David R.
Published: October 2005

Free-field release from masking was studied as a function of the spatial separation of a signal and masker in a two-interval, forced-choice (2IFC) adaptive paradigm. The signal was a 250-ms train of clicks (100/s) generated by filtering 50-μs pulses with a TDH-49 speaker (0.9 to 9.0 kHz). The masker was continuous broadband (0.7 to 11 kHz) white noise presented at a level of 44 dBA measured at the position of the subject’s head. In experiment I, masked and absolute thresholds were measured for 36 signal source locations (10° increments) along the horizontal plane as a function of seven masking source locations (30° increments). In experiment II, both absolute and masked thresholds were measured for seven signal locations along three vertical planes located at azimuthal rotations of 0° (median vertical plane), 45°, and 90°. In experiment III, monaural absolute and masked thresholds were measured for various signal–masker configurations. Masking-level differences (MLDs) were computed relative to the condition where the signal and mask were in front of the subjects after using absolute thresholds to account for differences in the signal’s sound-pressure level (SPL) due to direction. Maximum MLDs were 15 dB along the horizontal plane, 8 dB along the vertical, and 9 dB under monaural conditions.
Acoustics of King Abdullah Mosque
Authors: Abdelazeez Mohamed K. , Hammad Riziq N. , Mustafa Ahmed A.
Published: October 2005

This paper presents the acoustical problems associated with a huge mosque that has been built recently in Amman, Jordan. These problems include very high reverberation time values inside the mosque, reaching more than 15 s at midfrequencies, and more than 22 s for all frequencies below 500 Hz. In addition, the articulation index was very low and the ambient noise level was very high. These conditions produced an unacceptable acoustic environment for this place, and their reduction was essential. To remedy these problems, most of the interior surfaces of the mosque were treated using appropriate types of materials. Final measurements indicate that the reverberation time in the midfrequencies is around 1 s. Furthermore, the use of an electroacoustic system provides an almost uniform sound level inside the mosque. The articulation index measurements show good to excellent response.
Controlling interoffice sound transmission through a suspended ceiling
Authors: Halliwell R. E. , Quirt J. D.
Published: October 2005

A simple, economical technique is discussed to improve the noise reduction between adjacent offices where the dominant sound transmission path is through the suspended ceiling and the common plenum above the ceiling. A series of laboratory measurements has been made to determine the important physical parameters associated with using a stack of absorptive batts as a sound barrier. These are compared with measurements made of an installation in a commercial office building. Further studies are required to evaluate the effect on air quality.
An equivalent circuit description of two coupled vibrations
Authors: Söderkvist Jan
Published: October 2005

Two adjacent mechanical systems usually affect each other. This is particularly noticeable if their resonance frequencies are almost equal. A simple way of describing this phenomenon, for second-order mechanical systems, is derived in this article. It is shown that the mechanical coupling can be described with the help of an ordinary electric equivalent circuit. The components in the equivalent circuit are easily measured electrically, for instance, with the help of piezoelectric and magnetostrictive devices, strain gauges or with an impedance meter. It is also shown how useful information can be extracted from measurements in a simple way. Predictions of the vibration amplitude of a second system, caused by a first system, can easily be made, if the values of the equivalent components are known. The behavior of the systems in the absence of the coupling can also be predicted from the (electric) measurements.
Vibration modes of mass-loaded planoconvex quartz crystal resonators
Authors: Benes Ewald , Schmid Michael , Kravchenko Victor
Published: October 2005

Layered piezoelectric resonators exhibit a complex spectrum of eigenfrequencies, which can be understood better if the associated vibration patterns are examined. For a closer insight into such a system, planoconvex AT-cut quartz crystals with a thick layer of copper on one side are investigated experimentally. Since presently no comprehensive three-dimensional theory of layered resonators is available, the experimental results can be compared only with one-dimensional descriptions of layered resonators or with theoretical models for unloaded contoured quartz crystals. The anharmonic spectrum of the crystals is used to find a formula by which the eigenfrequency of the corresponding infinite plate can be determined from measured frequencies of planoconvex crystals. If this correction is applied to experimental frequency spectra of composite quartz-film resonators, excellent agreement with the one-dimensional model is found. As theoretically predicted, also even harmonic overtones of heavily loaded crystals can be excited electrically. The vibration patterns are examined with an ultrasensitive laser-speckle technique. The measurements of the odd harmonic overtones agree well with the theory of energy trapping in planoconvex quartz crystals. An increase of the crystal’s active area with increasing mass load is observed. The even overtones frequently exhibit no such energy trapping; in these cases, unusual vibration patterns occur.
A wide bandwidth spectrometer for rapid ultrasonic absorption measurements in liquids
Authors: Challis Richard E. , Harrison John A. , Holmes Andrew K. , Cocker Richard P.
Published: October 2005

An acoustic near plane-wave absorption spectrometer has been developed for use in small samples of liquid (30 ml) over bandwidths of up to 60 MHz, using a two transducer short-pulse transmission technique. The instrument is controlled by computer, and on-line digital signal processing is used to correct for transducer insertion, radiation coupling, and the transient responses of transmitter and receiver electronics. The raw data acquisition time is short and the instrument in its present form could be used to estimate absorption at 100-ms intervals. The instrument can be used on both stationary chemical systems and systems undergoing chemical reaction. Experimental results are presented that show excellent agreement with absorption measurements by traditional (slower) techniques.
Temporal integration and multiple looks
Authors: Viemeister Neal F. , Wakefield Gregory H.
Published: October 2005

The decrease in detection and discrimination thresholds with increases in signal duration has often been taken to indicate that a process of relatively long-term temporal integration occurs in hearing. Two experiments are reported that suggest that no such process occurs. The first experiment is similar to the two-pulse experiment reported by Zwislocki [J. Zwislocki, J. Acoust. Soc. Am. 32, 1046–1059 (1960)] in which the threshold in quiet for a pair of brief pulses is measured as a function of the temporal separation between them. Our data indicate that power integration occurs only for separations less than approximately 5 ms. For separations larger than 5–10 ms, thresholds do not change with separation and the pulses appear to be processed independently. In the second experiment, brief 1-kHz tone pulses separated by 100 ms are presented during gaps in a wideband noise. The threshold for a pair of pulses is lower than that for either pulse presented alone, indicating that some type of ‘‘integration’’ occurs. However, the threshold for the pulse pair is not affected by changes in the level of the noise during the interval between the pulses. These data are inconsistent with the classical view of temporal integration that involves long-term integration. They are consistent with the notion that the input is sampled at a fairly high rate and that these samples or ‘‘looks’’ are stored in memory and can be accessed and processed selectively. This multiple-look model can account for the data from the present experiment and also can account for the data on temporal integration for tones and noise. The model provides a framework for describing resolution-related phenomena, such as gap detection, without resorting to multiple time constants.
Turning on a tone
Authors: Hartmann William Morris , Sartor Dan C.
Published: October 2005

It is possible to choose the starting phase of a pure tone in a way that minimizes the onset noise when the tone is turned on abruptly. A spectral model shows that when the tone has a low frequency, minimum onset noise is expected for a starting phase of zero (turning on a sine tone) but when the tone has a high frequency, minimum onset noise is expected for a starting phase of ±90 deg (turning on a cosine tone). Listening experiments confirm the above expectations and show that the transition between low- and high-frequency domains is sharp and depends upon both the electroacoustical transducer and the individual listener.
Dynamic processes in the precedence effect
Authors: Freyman Richard L. , Clifton Rachel K. , Litovsky Ruth Y.
Published: October 2005

Three experiments were conducted to investigate the dependence of echo suppression on the auditory stimulation just prior to a test stimulus. Subjects sat in an anechoic chamber between two loudspeakers, one which presented the ‘‘lead’’ sound, and the other the delayed ‘‘lag’’ sound. In the first experiment, subjects reported whether or not they heard an echo coming from the vicinity of the lag loudspeaker during a test click pair. In seven of nine listeners, perception of the lagging sound was strongly diminished by the presence of a train of ‘‘conditioning’’ clicks presented just before the test click. Echo threshold increased (subjects were less sensitive to echoes) as the number of clicks in the train increased from 3 to 17. For a fixed number of clicks, the effect was essentially independent of click rate (from 1/s through 50/s) and duration of the train (from 0.5 through 8 s). A second experiment demonstrated a similar buildup of echo suppression with white noise bursts, regardless of whether the bursts in the conditioning train were repeated samples of frozen noise, or were independent samples of noise. Using an objective procedure for measuring echo threshold, the third experiment demonstrated that both lead and lag stimuli must be presented during the conditioning train in order to produce the buildup of suppression. When only the lead sound was presented during the conditioning train, the perceptibility of the lag sound during the test burst appeared to be enhanced.
Fourth-order spectra of Gaussian amplitude-modulated sinusoids
Authors: Dwyer Roger F.
Published: October 2005

Propagating underwater signals are sometimes amplitude modulated by the medium or other physical effects. Since this is a multiplicative phenomenon, the resulting spectrum is a convolution of the spectra of the modulation and the desired signal. A new method based on the spectrum of a special case of the fourth-order cumulant is proposed to extract the desired signal. It is shown that the special case of the fourth-order cumulant is independent of the covariance of a Gaussian modulating function, and therefore it can extract the desired signal even when the modulating process is Gaussian white noise. Convergence equations are derived which show that the fourth-order cumulant and its special case will converge to their asymptotic forms as the data length increases. The spectrum of the special case of the fourth-order cumulant is also derived at the output of a low-pass filter. To demonstrate these theoretical results, an experiment was conducted. A sinusoid was modulated by white Gaussian noise and transmitted through the water and received on an omnidirectional hydrophone. The second-order spectrum, the spectrum of the special case of the fourth-order moment and the spectrum of the special case of the fourth-order cumulant were estimated from the filtered data. The experiment corroborated the theoretical results by showing that the second-order spectrum could not extract the sinusoidal frequency, but the spectrum of the special case of the fourth-order moment and the spectrum of the special case of the fourth-order cumulant could. Simulations are included which further corroborate the theoretical results.
Distributed transducer vibration control of thin plates
Authors: Burke Shawn E. , Hubbard James E.
Published: October 2005

This paper presents an energy-based analysis of the application of distributed, biaxial piezoelectric transducers for the vibration measurement and control of thin plates, subject to general boundary conditions. The method exploits plate modal symmetry and boundary integral representations of key parameters to choose spatial weightings for distributed sensors and actuators. The technique may be used to develop transducer spatial distributions and temporal compensators to simultaneously measure and damp multiple plate modes, as well as target selected modes. Sensor and actuator distributions facilitating all-mode measurement and control are developed for various boundary conditions. For the purposes of illustration, models based on the piezoelectric polymer film transducer polyvinylidene fluoride (PVF2) are used.
Monomolecular organic film effect on wind-driven waves deduced from ultrasound scattering
Authors: Pogorzelski Stanislaw J.
Published: October 2005

A spectrum of low-frequency amplitude fluctuations of the ultrasonic signal scattered at an air flow-created water surface covered with monomolecular crude oil origin films of well-defined viscoelastic properties was examined under laboratory conditions. The presence of an oil film causes a shift of the peak frequency toward higher frequencies and increases the fall-off on the high-frequency band of the spectrum if compared to clean surface scattering. The effect turned out to be univocally related to rheological parameters of the spread film. Functional relations between the spectra features and theoretically computed wave-damping abilities of the studied films by means of the Marangoni damping theory have been established.
Interference studies of acoustic pressure and intensity fields of two simple sources
Authors: Ham S. Y. , Kim W. S. , Prasad M. G.
Published: October 2005

In the application of acoustic intensity method to study the acoustical field of a source, the interference due to a secondary source or a reflecting boundary becomes important. This study deals with the formulations of interference of acoustical pressure and intensity fields of two simple sources. The intensity interference is investigated in terms of both radial and transverse components. The predicted pressure-intensity interference by the formulations agrees well with measurements carried out in an anechoic chamber.
A retracted boundary integral equation for exterior acoustic problem with unique solution for all wave numbers
Authors: Hwang Jyh-Yeong , Chang San-Cheng
Published: October 2005

A regular integral equation based on the surface source distribution method is developed to solve the exterior acoustic radiation and scattering problems. This integral equation, formed by seeking the equivalent mixed-layer potential distributed over an auxiliary surface retracted from the actual boundary, is uniquely solvable and has nonsingular kernel function. Hence, it is more amenable to numerical implementation and can circumvent the difficulties of singularity, nonuniqueness, and slope discontinuity of the conventional integral equation formulations. In contrast to the behavior of Fredholm integral equations of the second kind, the discretization of a regular integral equation will not result in a diagonally dominant coefficient matrix. To overcome the undesirable numerical instability, the optimal selection of the interior source surface is investigated through error estimate of the numerical integration. The versatility and accuracy of the proposed formulation are demonstrated by numerical examples involving spheres, prolate spheroids, and finite cylinders.
Band structure of materials suitable for production of pico and subpicosecond optoacoustic pulses
Authors: Dharamsi A. N. , Hassam A. B.
Published: October 2005

A previous discussion [J. Acoust. Soc. Am. 85, 1560–1568 (1989)] on the energy band structure of target materials, suitable for generation of ultrashort optoacoustic pulses by photostriction, is extended and formalized. Details of the band structure necessary to suppress thermalization by holes are included. It is pointed out that the material should exhibit suitable gaps between valence bands in addition to having suitable gaps between conduction bands. The conditions that must be satisfied in order to prevent thermalization by electrons as well as holes, a key feature necessary in the production of ultrashort pulses, are formalized. Some examples of materials approaching an ‘‘ideal’’ band structure are given.
The effect of wall elasticity on the properties of a Helmholtz resonator
Authors: Photiadis Douglas M.
Published: October 2005

The effect of compliant walls on the properties of a Helmholtz resonator is examined. The effective stiffness of the resonator is decreased by the wall compliance, while the effective mass is unchanged to leading order. The radiation resistance is also decreased due to a cancellation between the radiation from the cavity opening and the radiation from the cavity walls. This leads to a reduction in the cross section at resonance by the factor [Zs/(Zs+Z0f)]4, where Zs is the wall impedance and Z0f is the total fluid loading on the breathing mode of the cavity.
From touch to string vibrations. II: The motion of the key and hammer
Authors: Askenfelt Anders , Jansson Erik V.
Published: October 2005

This article describes an experimental study of the motion of the grand piano key and hammer. The motions were registered by means of an optical position measuring system. The measurements include typical key and hammer motions at different dynamic levels and for different types of ‘‘touch.’’ Also, the accelerating force on the hammer before release (‘‘let-off’’), and the following free motion of the hammer were investigated. Resonances in the hammer were detected and examined by modal analysis. A possible influence of the pianist’s touch on the string vibrations via the hammer resonances is discussed.
Vocal quality factors: Analysis, synthesis, and perception
Authors: Childers D. G. , Lee C. K.
Published: October 2005

The purpose of this study was to examine several factors of vocal quality that might be affected by changes in vocal fold vibratory patterns. Four voice types were examined: modal, vocal fry, falsetto, and breathy. Three categories of analysis techniques were developed to extract source-related features from speech and electroglottographic (EGG) signals. Four factors were found to be important for characterizing the glottal excitations for the four voice types: the glottal pulse width, the glottal pulse skewness, the abruptness of glottal closure, and the turbulent noise component. The significance of these factors for voice synthesis was studied and a new voice source model that accounted for certain physiological aspects of vocal fold motion was developed and tested using speech synthesis. Perceptual listening tests were conducted to evaluate the auditory effects of the source model parameters upon synthesized speech. The effects of the spectral slope of the source excitation, the shape of the glottal excitation pulse, and the characteristics of the turbulent noise source were considered. Applications for these research results include synthesis of natural sounding speech, synthesis and modeling of vocal disorders, and the development of speaker independent (or adaptive) speech recognition systems.
Spike discharge properties that are related to the characteristic frequency of single units in the frog auditory nerve
Authors: Ronken Don A.
Published: October 2005

Single units from the auditory nerve of frogs and toads have their receptor cells located in two separate sensory organs that provide disjoint frequency ranges. The amphibian papilla (ap) provides units with characteristic frequency (CF) in the low- and mid-frequency regions and the basilar papilla (bp) provides units with high CF. There are gross differences in both the mechanical design and innervation patterns of the two organs, so that one might expect discharge properties for units with different CF to differ in many respects. However, there have been few reports of response attributes that correlate strongly with CF for units in the mid- and high-CF regions. Measurements of automated tuning curves from 250 units in Rana pipiens show that W10 dB, the bandwidth of the tuning curve measured 10 dB above CF threshold, is consistently larger for high-CF units than for low- and mid-frequency units. When units are classified into three groups by an objective statistical method using only CF and W10 dB measurements, the groups appear to correspond reasonably well with the low-, mid-, and high-frequency categories identified in many other studies.
Power output minimization and power absorption in the active control of sound
Authors: Elliott S. J. , Joseph P. , Nelson P. A. , Johnson M. E.
Published: October 2005

Active minimization of total power output and active absorption of sound power are analyzed, using a general impedance-based approach, for an array of controllable secondary sources and an array of original primary sources. When the total power output of the two arrays is minimized, and the primary source array is all in phase, the power output of each of the secondary sources is found to be exactly zero. When the power absorption of the secondary source array is maximized, the net power output of the primary source array can be either reduced or increased, compared to that in the absence of control, depending on the properties of the transfer impedances. If the primary and secondary sources are well coupled (as is the case when they are spaced less than a quarter wavelength apart in free-space or when they are in an enclosure excited near the natural frequency of a lightly damped mode) minimizing the total power output gives worthwhile reductions in the radiated power of the primary source. Maximizing the power absorption of the secondary source under these conditions, however, can considerably increase the power output of the primary source. If the sources are well separated, compared with the wavelength, in the free-field, or are placed in a diffuse sound field in an enclosure, the coupling between the sources is weak. Under these conditions the secondary source can effect little reduction in the power output of the primary source. Although acoustic power can still be absorbed by the secondary source under such circumstances, the amount of absorbed power will always be small compared with the power output of the primary source.
The influence of atmospheric absorption on loudness and the A-weighted sound-pressure level
Authors: Jorasz Urszula , Makarewicz Rufin , Jarzȩcki Jan
Published: October 2005

Criteria based on Zwicker’s model of loudness and the A-weighted sound-pressure level are used to find the source–receiver distance at which atmospheric absorption becomes significant. The problem is studied for a wide range of temperature and relative humidity variations. It is found that both criteria are nearly equivalent. For the majority of environmental noise sources, including motor vehicles and trains, air absorption cannot be neglected at distances beyond a few hundred meters.
The minimum multimodal radiation efficiency of baffled finite beams
Authors: Cunefare Kenneth A.
Published: October 2005

A technique for deriving the optimal surface velocity distribution on the surface of a finite baffled beam has been developed. The optimal velocity distribution minimizes the radiation efficiency of the beam for a specified maximum permissible mode and frequency. A modal expansion of the surface velocity in terms of unknown modal amplitude coefficients, the Rayleigh integral, and a far-field intensity integration are employed to obtain a quadratic expression for the radiation efficiency of the beam. Application of a suitable constraint to avoid trivial solutions leads to an eigenvalue problem identical in form to the Rayleigh quotient employed in dynamic mechanical systems. The eigenvector of modal amplitude coefficients corresponding to the lowest eigenvalue yields the minimum radiation efficiency, while the eigenvalue itself is the actual value of the minimum radiation efficiency. Near and below coincidence, the optimal eigenvector of modal amplitude coefficients yields a radiation efficiency significantly less than the radiation efficiency of any single modal component acting alone. Simply supported and clamped–clamped boundary conditions are considered, and numerical examples are presented for each.
Effects of random deviations in interface properties on the propagation of ultrasound in thick composites
Authors: Lu Yichi , Achenbach Jan D.
Published: October 2005

Propagation of ultrasound across a solid layer with equally spaced parallel interfaces is studied by using a transfer matrix method. For a layer with identical interfaces the propagation of ultrasound is governed by a dispersion relation, which displays passing and stopping bands in the frequency domain. For a layer with interfaces that have random deviations from mean interface properties, the Fürstenberg theorem and Monte Carlo simulation have been used to study propagation of ultrasound across the layer. It has been shown that at all frequencies there is an exponential decay in the amplitude of the transmitted wave. This decay, which increases with increasing frequency, defines a localization phenomenon, since wave motion will be confined to the insonified side of the layer.
Seismo/acoustic propagation through rough seafloors
Authors: Dougherty Martin E. , Stephen Ralph A.
Published: October 2005

This paper addresses the scattering of seismoacoustic energy from rough water–solid interfaces. A two-dimensional elastic finite difference method with a velocity-stress formulation is used for all of these models, including all phases, multiples, interface, and interference waves. Initial sinusoidal seafloor models at 15 grid points per wavelength (ppw) show that even medium slopes can greatly increase the amount of energy (especially P to S converted energy) which is transmitted into the bottom. Scattering from microroughness (stair-step definition of a sloping seafloor) is significant for 10-m steps with a pressure pulse source of 10-Hz center frequency. Additional models with much finer grids (30 and 60 ppw) were computed to decrease the microroughness scattering and to check the accuracy of scattering from 10-m steps. Most of the microroughness scattering disappears for the 60-ppw model. Scattering strength is similar for all models with 10-m microroughness. Reciprocal models at 15 and 30 ppw (both with 10-m stair steps) show very good agreement. An important conclusion of this work is that the specification of complex seafloors requires a much finer grid than is necessary for numerical stability and accuracy. This will be true for other numerical methods as well.
Sound scattering by a wedge-shaped protuberance.
Authors: Chu Dezhang
Published: October 2005

The problem of the diffraction of sound by a wedge-shaped (triangular) protuberance is investigated. The concept of directional diffraction amplitude is introduced in this paper to obtain a high-frequency approximate solution for such a problem (ka≫1). The solution takes into account all orders of multiple diffractions among the vertices and can further be used in describing scattering by corresponding deformed wedge protuberance of finite length. The numerical results are presented. It is shown that at low-frequency, multiple diffractions dominate while at higher frequency the single diffractions from the wedge vertices become dominant. The simple closed-form solution for a hard strip, derived using present method, is compared with published data [Medwin etal., J. Acoust. Soc. Am. 72, 1005–1031 (1982)] to show the importance of multiple diffractions.
Fluid effects on velocity and attenuation in sandstones.
Authors: Gist Grant A.
Published: October 2005

Measurements of ultrasonic velocity and attenuation in sandstones with a variety of saturating fluids are compared with the predictions of Biot’s theory of porous media acoustics. The data show systematic deviations from Biot theory as a function of pore fluid viscosity. Two non-Biot attenuation mechanisms are needed to explain the data: local flow in microcracks and enhanced attenuation from pore-wall roughness. A model calculation of attenuation with pore-wall roughness shows that attenuation in rocks can be many times larger than Biot predictions. This attenuation enhancement explains the inability to detect a Biot slow wave in fluid-saturated rocks and the observed correlation between ultrasonic attenuation and clay content in sandstones. The non-Biot attenuation mechanisms are negligible when extrapolated to the lower frequencies of geophysical field measurements, so ultrasonic attenuation in rocks provides no information about attenuation at the field scale.
Acoustics of bubbly sediments with a distribution of bubble sizes.
Authors: Hawkins J. A. , Bedford A.
Published: October 2005

A model for a saturated, porous elastic medium containing bubbles of gas [J. Acoust. Soc. Am. 73, 409–417 (1983)] has been combined with a model for a bubbly liquid with a bubble population whose radii vary continuously over a known distribution [J. Acoust. Soc. Am. Suppl. 1 88, (1990)] to obtain an acoustical model for saturated sediments containing a distribution of bubble sizes. The dispersion relation has been obtained and the phase velocity and attenuation have been calculated as functions of frequency for several distributions of bubble sizes. The presence of a distribution of bubble sizes tends to smooth the effects of bubble resonance on the phase velocity and attenuation in comparison with a single bubble size, but the main qualitative effects of bubble resonance remain intact.
Group velocity maxima discrepancies on longitudinal waves in thick elastic waveguides.
Authors: Chamuel Jacques R.
Published: October 2005

Fundamental understanding of elastic wave propagation in thick elastic waveguides is important for quantitative studies on Arctic underwater seismoacoustics and nondestructive testing. The first arriving high-frequency wave train propagating in a plate or rod has been attributed to high-order symmetric normal modes. Although the phase velocity dispersion curve of each of the high-order modes has a point at the bulk compressional wave velocity, its corresponding group velocity may be much lower. Tolstoy and Usdin (J. Acoust. Soc. Am., 1957) showed that the group velocity maxima for normal modes in a plate approach the compressional wave velocity with increasing mode number. Using a 500-wavelengths-long aluminum rod, experimental results with a 0.15% accuracy are obtained showing that in a limited high-frequency band (not very high frequencies kH≊42) the measured group velocity of the first arriving wave is identical to the bulk compressional wave velocity, which is about 4% greater than the exact normal mode group velocity maximum at the same frequency. Results on elastic wave propagation in floating plates and ridges are also presented. Implications of the findings are discussed together with a hypothetical explanation. [Work supported by ONR.]
Japanese listeners are less influenced by vision than Americans in speech perception.
Authors: Sekiyama Kaoru , Tohkura Yoh’ichi
Published: October 2005

Some cultural difference in the effects of visual (lip-read) information on face-to-face speech perception was observed. When presented a video recording of a talking face in which audio signals were dubbed onto video signals for incongruent syllables, robust visual effects (‘‘McGurk effect’’) have been reported in English speaking cultures. The present experiments, however, showed that Japanese listeners were much less influenced by visual cues than Americans. This was examined by testing ten Japanese (experiment 1) and ten American (experiment 2) subjects with ten Japanese syllables (/ba/, /pa/, /ma/, /wa/, /da/, /ta/, /na/, /ra/, /ga/, /ka/: ten audio × ten visual=100 audio–visual stimuli), and ten American subjects with ten English syllables (experiment 3). While Americans showed considerable visual influence for both Japanese and English syllables, Japanese listeners heard the syllables correctly with little visual influence. [Work supported by Nissan Science Foundation.]
The acquisition of a new phone: The production of Mandarin /f/ and /x/ by native speakers of Amoy (Taiwanese).
Authors: Peng Shu-hui
Published: October 2005

The present study examines the patterns of interference between first and second language by comparing the production of a Mandarin phone [f] (a ‘‘new’’ phone) with another Mandarin phone [x] (which is ‘‘similar’’ to an Amoy phone [h]) by three groups of native Amoy subjects differentiated by proficiency in Mandarin. Their Mandarin productions were also compared to those of Mandarin monolinguals. In general, native Amoy speakers interpreted Mandarin [f] and [x] in terms of their first language phonetic categories [hw] and [h], but showed different patterns of interference for different proficiency levels. The least proficient simply substituted the Amoy phones for the Mandarin. More proficient speakers could approximate the Mandarin monolingual phonetic norm for the ‘‘new’’ phone /f/ better than that for the ‘‘similar’’ phone /x/. In addition, the most proficient showed some interference from Mandarin [x] in their Amoy productions.
Phonetic and phonological realizations of voiceless stops in English.
Authors: Cooper André M.
Published: October 2005

Traditionally, the presence or absence of aspiration in English has been accounted for using rules that manipulate abstract phonological features which make crucial reference to the vocal folds. Such an account implies that the articulators work in service of aspiration categories by controlling glottal width and/or the relative timing of oral and laryngeal gestures. Acoustic and fiberoptic data from the present study show that oral-laryngeal timing is indeed under articulatory control but not necessarily for the purpose of generating specific aspiration categories. Instead, these results suggest that the extent of aspiration-related devoicing following voiceless stops is primarily by-product of the effect of suprasegmental parameters on intra-articulator timing, rather than the goal of intra-articulator timing. In other words, the extent of devoicing following voiceless stops appears to be predictable from independently motivated generalizations about the effects of continuous prosodic variation on oral and laryngeal gestures and on their coordination. If these generalizations are sufficient to describe the physical realization of voiceless stops, they obviate the need for an aspiration rule and for a separate feature to distinguish aspirated from unaspirated stops in English.
Effect of relative amplitude of frication on perception of place of articulation.
Authors: Hedrick Mark S. , Ohde Ralph N.
Published: October 2005

The amplitude of frication relative to vowel onset amplitude in the F3 and F5 formant frequency regions was manipulated for the synthetic fricative contrasts /s/–/sh/ and /s/–/θ/, respectively. The efficacy of this relative amplitude manipulation on listeners’ perception of place of articulation was tested as a function of vowel contexts /i u ɑ /, frication durations of 30 to 140 ms, conflicting formant transitions, and variations in gross frication spectral shape and formant transitions appropriate to place of articulation. The results showed that the relative amplitude cue was invariantly perceived across vowel context and frication duration, overrode context-dependent formant transition cues, and exerted primary influence on perception with variations in formant transitions and gross frication spectral shape appropriate to place of articulation. The results support a theory indicating that acoustic correlates of sound features exist, which are invariantly perceived. [Supported by NIH, DC00464.]
Application of the phase gradient autofocus algorithm to time delay estimation in linear arrays.
Authors: Wahl D. E.
Published: October 2005

For the purpose of localizing a distant noisy target, estimating the time delay of a wave front as it traverses across the sensors in a SONAR array is of considerable interest. This paper studies the application of the phase gradient autofocus (PGA) algorithm originally developed for extracting degrading phase errors in synthetic aperture radar (SAR) images to the time delay estimation problem in large linear arrays. It is well known that an efficient time delay estimation procedure consists of multiple cross correlations (one for each sensor pair) followed by a linear minimum-variance estimator. Monte Carlo simulation examples are presented that indicate the performance of the PGA method approaches the performance of the multiple correlator method at signal-to-noise ratios (SNRs) exceeding 0 dB with a substantial reduction in computational cost. Furthermore, PGA can easily take advantage of apriori knowledge regarding source bearings or array shape (if not perfectly linear) in order to improve the time delay estimates.