bluuebunny/crossref_metadata_2025 huggingface dataset:
Dependence of the electromechanical coupling coefficient on the width-to-thickness ratio of plank-shaped piezoelectric transducers used for electronically scanned ultrasound diagnostic systems
Authors: Sato J. , Kawabuchi M. , Fukumoto A.
Published: October 2005

A finite element analysis method is used to obtain the electromechanical coupling coefficient ke for plank-shaped piezoelectric transducers with a width W to thickness T ratio of not more than two. Calculation results for typical piezoelectric ceramics show that there exist maximum values of ke at certain values of W/T. For PCM-5R material the maximum value of ke is 0.69 at a W/T of 0.6. It is shown that only one vibrational mode is very strongly coupled around this value of W/T. This vibrational mode is very useful for application to electronically scanned arrayed transducers.
Objective measures for speech quality testing
Authors: Barnwell Thomas P.
Published: October 2005

This paper presents a discussion of the philosophy and practice of speech quality testing using objective measures. The emphasis in the paper is on the problems of designing effective objective quality measures and the inherent limitations of such measures. Both traditional and recent techniques are discussed, along with the issues of implementation and evaluation. Experimental results on the correlation between objective quality measures and subjective quality measures are also presented.
Flexural wave baffling
Authors: Ko Sung-Hwan , Sherman Charles H.
Published: October 2005

The effectiveness of acoustic baffles against flexural wave noise is discussed using a plane layer model consisting of an infinite plate, a fluid layer representing the baffle, and an outer plate which may be called the signal conditioning plate.
Acoustical analysis of the auditory system of the cricket T
e
l
e
o
g
r
y
l
l
u
s c
o
m
m
o
d
u
s (Walker)
Authors: Fletcher N. H. , Thwaites Suszanne
Published: October 2005

The basic auditory physiology of crickets, and particularly of Teleogryllus commodus (Walker) is examined and its behavior simulated by electrical analog networks, beginning from the simplest possible model and progressing by stages to the full system found in the real insect. It is found that the attenuation of sound in the auditory trachea plays a crucial role in the mechanism for directional hearing in even the simplest model and that the tracheal diameter is in fact appropriate to produce the desired attenuation. In a more complex model in which it is recognized that the auditory system probably responds to pressure changes in the tracheal sacs underlying the tympana rather than simply to tympanic motion, it is found that the phase shift produced by the combined effects of the central septum and the adjoining cavities leading to the spiracles is also important to hearing directionality. The final model which includes both tympana and spiracles is able to simulate both the hearing directionality and, in part, the frequency selectivity of the system. It appears, however, that a large measure of the observed frequency selectivity is due to some form of selectivity in the neural transducers themselves rather than in the simple acoustic components of the system.
The perception of fundamental frequency declination
Authors: Pierrehumbert Janet
Published: October 2005

A series of experiments was carried out to investigate how fundamental frequency declination is perceived by speakers of English. Using linear predictor coded speech, nonsense sentences were constructed in which fundamental frequency on the last stressed syllable had been systematically varied. Listeners were asked to judge which stressed syllable was higher in pitch. Their judgments were found to reflect normalization for expected declination; in general, when two stressed syllables sounded equal in pitch, the second was actually lower. The pattern of normalization reflected certain major features of production patterns: A greater correction for declination was made for wide pitch range stimuli than for narrow pitch range stimuli. The slope of expected declination was less for longer stimuli than for shorter ones. Lastly, amplitude was found to have a significant effect on judgments, suggesting that the amplitude downdrift which normally accompanies fundamental frequency declination may have an important role in the perception of phrasing.
Short-term spectral effects in pure-tone forward masking
Authors: Widin Gregory P. , Viemeister Neal F.
Published: October 2005

Measurements of the masking function with different masker envelopes suggest that short-term spectral broadening at offset affects the frequency extent of forward masking, at least for masker frequencies above the probe frequency.
The effects of aging on the stapedius reflex thresholds
Authors: Silman Shlomo
Published: October 2005

The acoustic reflex thresholds for broadband noise and 500-, 1000-, and 2000-Hz activating signals were measured in a group of young normal hearing adults and a group of elderly normal hearing subjects. The results indicated that the acoustic reflex thresholds for tonal activating signals in the young subjects were similar to those in the elderly subjects. However, the acoustic stapedius reflex thresholds for broadband noise activating signals is significantly higher in the elderly subjects than in the young. These differences were explained in light of Bredburg’s findings [Acta Otolaryngol. Suppl. 236, 1–135 (1968)] regarding degeneration of outer hair cells as a function of aging.
First-order statistics for finite bandwidth multipath signals with and without frequency or phase modulation
Authors: Mikhalevsky Peter N.
Published: October 2005

The phase-random model of multipath acoustic propagation is used to derive the first-order probability densities for the time rate-of-change of the short time average mean-square pressure ?, and the time rate-of-change of the level in decibels of the short time average mean-square pressure ?. It is shown that the probability densities for the signal amplitude, and amplitude rate are insensitive to frequency or phase modulation of the signal by the source, but that the density for the time rate-of-change of the multipath phase ?, is sensitive to such modulation. Because the finite bandwidths of acoustic signals can be modeled by uniform frequency modulation, the analysis presented applies to this problem as well. It is shown that bandwidth effects can be neglected only if B≪2ν, where B is the signal bandwidth, and ν2 is the single path mean-square phase rate. This inequality provides a useful definition of what is meant by ’’narrow band’’ as it applies to phase-random multipath propagation. It is also shown that the density for ? depends only on ν, while the density for ? depends on ν and parameters of the modulation. A potentially powerful technique is developed for determining source bandwidth and parameters of the source modulation, minus the effects of oceanic fluctuations, from the received multipath signal. The analytical results are compared with a computer simulation, and data from experiments in the ocean with extremely favorable results.
A method for modeling perforated tube muffler components. II. Applications
Authors: Sullivan Joseph W.
Published: October 2005

This paper is the second of two papers describing a method for modeling muffler components having perforated flow tubes, as for example those found frequently in automotive applications. In the first paper the theoretical model was developed, whereas here the theory is applied to demostrate specifically the utility and potential of the model. The applications are idealized in the sense that effects which occur simultaneously in perforated-tube mufflers are treated separately. These effects are (1) the nonlinear impedance of the perforation due to finite amplitude sound pressure, and (2) the change in impedance of the perforation with mean flow. The first effect is demonstrated with a straight through resonator, and the second with a cross-flow chamber. Predicted results for transmission loss in both cases compared quite well with measurements. Crucial to the success of the modeling was a proper description of the perforate impedance. The confidence instilled by the results prompted an inquiry into the nature of the two muffler components. It was determined by modeling that, contrary to popular opinion, these devices can be very dissipative, even though they contain no recognizable dissipative materials. The controlling mechanism is the high resistivity of the perforation induced by the acoustic/flow environment.
Derivation of the acoustic wave equation in the presence of gravitational and rotational effects
Authors: DeSanto John A.
Published: October 2005

We derive, from first principles, the multidimensional partial differential equation obeyed by the underwater pressure field in the presence of gravitational and rotational forces acting on the fluid medium. The result is valid for a sound speed which depends on all three spatial dimensions and time. For the special case of a purely depth-dependent sound speed the result reduces essentially to that of Tolstoy. The relationship to the internal wave equation is also presented, as well as other examples, including the effect of Rossby waves.
Predicting vocal frequency from selected physiologic measures
Authors: Shipp Thomas , Doherty E. Thomas , Morrissey Philip
Published: October 2005

Simultaneous physiologic measures were obtained on four young adult male subjects as they sustained phonation at seven frequencies within their modal-to-falsetto voice range. Data were analyzed using a multiple regression program to determine the contribution of each measure singly and in combination with other measures to the prediction of the resultant voice frequency. Results showed that by far the best predictor was cricothyroid muscle activity for both the pooled data model, and for each individual subject. The contribution of subglottal air pressure and thyroarytenoid muscle activity increased the variance explained by only 4% while the measure of vertical laryngeal position was a significant factor in only one subject’s predictive model. Partial models from the pooled data explained from 67% to 73% of the variance; whereas the obtained measures for individual subjects explained from 90% to 94% of the variance.
Sound transmission between absorbing parallel planes
Authors: Hurst C. J.
Published: October 2005

Partially absorbing parallel surfaces can be the dominant acoustical feature of many rooms. The sound fields in such rooms are not diffuse, which causes difficulty in predicting sound pressure levels. A method is developed for predicting sound pressure levels in these rooms. It rests on the prediction of sound pressure levels caused by a nondirectional source of known sound power radiating between absorbing parallel planes. The development proceeds from a geometrical acoustics viewpoint. Good correlation has been found between predicted and measured levels in existing rooms having simple geometries.
Detection of sinusoids in ocean acoustic background noise
Authors: Hodgkiss W. S. , Anderson V. C.
Published: October 2005

A common receiver structure for the detection of sinusoidal signals obscured by a noise background is the filter, square, and integrate processor. For this processor, an interpretation of postdetection integration gain is given in terms of a low-pass filtering of the noise power time series. Although a processing gain of 1.5 dB per integration interval doubling is predicted, subsequent analysis on the highly colored envelope spectrum of ambient ocean acoustic noise data in the kilohertz region shows that its nonstationarity significantly alters realizable processing gains for integration intervals of tens to hundreds of seconds.
Off-frequency listening and auditory-filter asymmetry
Authors: Patterson Roy D. , Nimmo-Smith Ian
Published: October 2005

The phenomenon of off-frequency listening, and the asymmetry of the auditory filter, were investigated by performing a masking experiment in which a 2.0-kHz tonal signal (0.4 sec in duration) was masked by a pair of noise bands, one below and the other above the tone. The noise bands were 0.8-kHz wide. The edges of the bands were very sharp, the spectrum level in the band was 40 dB SPL, and the masker was on continuously throughout the experiment. Tone threshold was measured as a function of the distances from the tone to the nearer edge of each noise band. It was assumed that conditions in which one noise band was near the tone and the other remote from the tone would encourage the observer to listen off frequency, that is, to center his auditory filter, not at the tone frequency, but at the frequency that optimizes the signal-to-noise ratio at the output of the filter. The threshold data were analysed with a power spectrum model of masking in which it was assumed that the general form of the filter shape was a rounded exponential (a pair of back-to-back, negative exponentials with the peak smoothed and the tails raised). The specific filter shape obtained by applying this model to the threshold data has a broad passband (a 220-Hz, 3-dB bandwidth), steep skirts (slopes of 100 dB/octave) and shallower tails (slopes of 30–50 dB/octave) that take over 30–35 dB down from the peak of sensitivity. The filter is asymmetric, with the lower branch slightly broader than the upper. The filter is shifted off frequency by more than half its bandwidth in some cases, and the shift can improve the signal-to-noise ratio by up to 5.0 dB.
Preliminary observations on the response of perioral single motor units to mechanical stretch
Authors: McClean Michael D. , Cooker Harry S.
Published: October 2005

This research represents part of a series of investigations into the function of mechanoreceptor feedback in lip motor control for speech. In the present study, precise mechanical stretches were applied to subjects’ lips while they held the firing frequency of a given single motor unit relatively constant using audio and visual feedback. Preliminary data indicate that mechanical stimulation produces a range of short and long latency excitatory and inhibitory effects in perioral motor units. Of particular interest are short latency inhibitory effects in the depressor labii inferior and platysma muscles. These short latency inhibitory effects suggest that the central organization of the perioral sensorimotor system may possess a form of reciprocal innervation. The operation of a circuit is described which permits improved experimental control over the timing of stretch application relative to moter unit discharge. Initial data collected with this circuit suggest that it may be effectively used to assess the time course of subthreshold excitability changes associated with individual motor units during their repeated discharge.
Production and perception of vowel length in spoken sentences
Authors: Nooteboom S. G. , Doodeman G. J. N.
Published: October 2005

A series of experiments was conducted to determine (1) the accuracy with which vowel segment durations in spoken sentences can be represented in auditory sensory storage and (2) the extent to which phoneme boundaries in the identification of phonemic vowel length in Dutch are affected by syntactic and/or auditory–phonetic context. In a preliminary production test it was found that durations of both long and short Dutch vowel phonemes in monosyllabic words embedded in sentences are systematically affected by word positions in the sentences. In an initial perceptual experiment, phoneme boundaries and slopes of identification curves were measured for 12 listeners in five different test utterances in a binary forced choice identification test. Perceptual accuracy of vowel duration perception as determined from the slopes of the identification curves corresponds on the average to a just-noticeable difference (JND) of about 5 ms with a test segment duration of about 90 ms. Phoneme boundary values are systematically affected by context in ways predictable from syntactic structure and the auditory–phonetic environment. In a second perceptual experiment it is shown that a major effect on phoneme boundary can be brought about by perceived properties of the test utterance following the monosyllable containing the test segment. In a third perceptual experiment it is shown that the difference between phoneme boundaries in utterance final syllable and in embedded syllable is related to the presence or absence of a perceived speech pause following that syllable. The results of these experiments are interpreted in terms of a simple decision model with a noisy auditory representation of embedded vowel duration, lasting a few hundredths of milliseconds, and a noiseless internal criterion for vowel length identification which is systematically affected by the auditory–phonetic environment.
Noise reduction by barriers on finite impedance ground
Authors: Isei T. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

The sound field due to a point source behind a barrier on ground of finite impedance has been calculated from five theories that differ mainly in their theoretical approach to diffraction and the model for ground impedance. These predicted values for the sound field have been compared with results measured outdoors using plywood barriers on different combinations of hard and soft ground. Each of these theories allows for interference due to differences between several paths of propagation, determined by the geometry of the source, receiver, barrier, and ground. One of these theories that shows good agreement with measurements, has been extended to calculate the sound spectrum level behind a barrier due to an incoherent line source, and further, to calculate the overall or A-weighted sound level for a known source spectrum. Results suggest that there is a significant effect, due to the presence of the ground, that is much greater than that due to absorptive properties of the barrier. Results also predict sound level reductions that differ from predictions using well-known barrier theories (most noticeably a smaller insertion loss): these differences can be of the order of 10 dB(A) depending on geometry, source spectrum, and acoustical condition of the ground.
Acoustic synthesis of a flowduct area discontinuity
Authors: Lambert R. F. , Steinbrueck E. A.
Published: October 2005

An experimental study of the acoustic pressure reflection coefficient at a sudden area expansion in a flowduct in regard to both magnitude and phase has been undertaken. The study was limited to low-flow Mach numbers, frequencies supporting plane-wave propagation, and an area transition ratio of 1:4. The magnitude of the coefficient is flow dependent and relatively insensitive to frequency while the phase is frequency dependent and relatively independent of flow. A semi-empirical analytical model has been symthesized on the basis of available information that incorporates both frequency characteristics and flow affects through second order in the Mach number. The Karal discontinuity correction is important and appears to be a valid representation of the reactive acoustic fields at sufficiently low Mach numbers. The flow primarily influences the acoustic impedance level of both the upstream and downstream ducts and secondarily the acoustic pressure and velocity coupling parameters.
Finite amplitude distortion of spherically diverging intense sound waves in air
Authors: Campanella Angelo J.
Published: October 2005

Waveform distortion in a free field of intense sinusoidal pressure waves propagating in air was measured along the axis of a 122-mm-diam plane piston source for four fundamental frequencies, 14.7, 24.6, 35.7, and 63.6 kHz. The acoustic pressure of the fundamental and harmonic components was measured versus source amplitude at distances from 0.15 to 2.00 m from the source at amplitudes up to 160 dB re 20 μPa. It was observed (1) that the pressure waveform reaches the stable form of an iterated shock at a smaller distance from the source for larger source pressure amplitudes, (2) that waveform distortion increases with frequency at a given source amplitude and a given distance, and (3) that a limiting level exists for the fundamental amplitude at a given point in a spherically diverging sound field with increasing source level. An empirical propagation relation due to Allen was further developed to include frequency dependence and air absorption. Complete shock formation was inhibited for the highest frequency sound field, presumably because of atmospheric molecular absorption.
Jet noise diagnostics: Spurious sound generated by hot-wire turbulence interaction
Authors: Richarz W. G.
Published: October 2005

Many attempts to measure source terms of jet noise by means of jet flow–jet noise cross correlations have been only partially successful. The major difficulty is suspected to be spurious ’’probe noise’’ generated by turbulence–sensor interaction. The present analysis predicts the effects of probe noise on measured cross correlations and cross-spectral densities. The description relies on Ribner’s self and shear noise model, a development of Lighthill’s theory of jet noise. Predictions are supported by jet noise–jet flow correlations measured with a hot wire and with a nonintrusive device: a Laser Doppler Velocimeter (LDV). The hot wires are found to generate spurious but well correlated noise. This leads to major errors in jet noise diagnostics of low-speed flows.
Theoretical and numerical Green’s function field solution in a plane multilayered medium
Authors: DiNapoli F. R. , Deavenport R. L.
Published: October 2005

An explicit general form is derived for the depth-dependent Green’s function occurring in the integral solution to the Helmholtz wave equation for range-independent layered media. This representation permits arbitrary location of the source and receiver. In addition, a technique, the Fast Field Program (FFP), for the evaluation of the integral solution is delineated. Examples of the use of both the formulation and the FFP to the problem of modeling underwater acoustic propagation loss versus range, where the source/receiver are in air/water, in water/bottom, and in a cross-layer surface duct, are discussed.
Shape oscillation and static deformation of drops and bubbles driven by modulated radiation stresses—Theory
Authors: Marston Philip L.
Published: October 2005

Deformations of drops and bubbles opposed by surface tension and driven by radiation stresses at the interface are calculated using spherical harmonic expansions for the radial and tangential stresses. Superimposed acoustic waves produce stresses which oscillate at the difference frequency ω of the waves in addition to static stresses. When the effects of viscosity on the acoustic waves are omitted, the tangential radiation stress vanishes; a procedure is proposed for calculating the radial stresses from the theory for ’’Acoustic Radiation Pressure on a Compressible Sphere’’ [K. Yosioka and Y. Kawasima, Acustica 5, 167–173 (1955)]. The calculation of the response assumes incompressible second-order flow and omits the body forces which are normally asociated with acoustic streaming. Resonance phase shifts and enhancements of the response should occur when ω is close to the natural oscillation frequency of a mode. Quadrupole resonance phase shifts and enhancements have been observed by the author [J. Acoust. Soc. Am. 67, 27–37 (1980)]. Diverse applications of the theory include the possibilities of: inference of the interfacial tension from the response; emulsification by exciting large amplitude oscillations; and deformation or splitting of bubbles by radiation stresses. The decay time of free oscillation is also calculated; a new term is found which is small but significant for drops surrounded by a liquid and supplements the theory for ’’The Oscillations of a Fluid Droplet Immersed in Another Fluid’’ [C. A. Miller and L. E. Scriven, J. Fluid Mech. 32, 417–435 (1968)].
Magnitude of the acoustic reflex for either homophasic (0°) or antiphasic (180°) binaural activating signals presented in a background of noise
Authors: Gorga Michael P. , Abbas Paul J. , Lilly David J.
Published: October 2005

The threshold of the acoustic reflex (TAR) and the magnitude of middle-ear muscle response were measured for a homophasic (0°) and an antiphasic (180°) 550-Hz tone in a background of in-phase noise. Signal-to-noise ratio ranged from −20 dB to +15 dB. Whereas previously reported data shows an effect of phase on the percept of loudness, no evidence of a phase effect was measured for acoustic-reflex responses. These results are interpreted as evidence against a relation between loudness and acoustic reflex for binaurally presented signals.
Perceptual invariance and onset spectra for stop consonants in different vowel environments
Authors: Blumstein Sheila E. , Stevens Kenneth N.
Published: October 2005

A series of listening tests with brief synthetic consonant–vowel syllables was carried out to determine whether the initial part of a syllable can provide cues to place of articulation for voiced stop consonants independent of the remainder of the syllable. The data show that stimuli as short as 10–20 ms sampled from the onset of a consonant–vowel syllable, can be reliably identified for consonantal place of articulation, whether the second and higher formants contain moving or straight transitions and whether or not an initial burst is present. In most instances, these brief stimuli also contain sufficient information for vowel indentification. Stimulus continua in which formant transitions ranged from values appropriate to [b], [d], [g] in various vowel environments, and in which stimulus durations were 20 and 46 ms, yielded categorical labeling functions with a few exceptions. These results are consistent with a theory of speech perception in which consonant place of articulation is cued by invariant properties derived from the spectrum sampled in a 10–20 ms time window adjacent to consonantal onset or offset.
Error propagation analysis of four sound-power measurement techniques
Authors: Russell G. A.
Published: October 2005

Error propagation equations are derived for four different sound-power measurement techniques: hemispherical freefield, reference source, reverberation time, and two surface. The analysis shows the hemispherical freefield and two-surface methods to be governed by the same error equation. Of the four methods examined, the reference-source method is shown to exhibit the strongest dependence on errors in measuring the space averaged sound pressure. The results obtained can be used in planning and executing more accurate sound-power measurements.
A comparison of acoustical performance between a new one-piece earphone cushion and the conventional two-piece MX-41/AR cushion
Authors: Michael Paul L. , Bienvenue Gordon R.
Published: October 2005

A new one-piece earphone cushion, model 51, that should afford more reliable hearing measurement data than the conventional two-piece MX-41/AR earphone cushion, has been developed by Telephonics Corporation. In particular, the material used for the one-piece cushion should be more stable over a long period of time than the sponge material used in the two-piece MX-41/AR cushion. In addition, the single material of the one-piece cushion is more easily compounded and thus easier to control than those materials used in the two-piece cushion, and the cementing operation required for the two-piece cushion is avoided. The acoustical performances of the one- and two-piece cushions mounted on a TDH-39 earphone were compared by threshold-loudness-balance and coupler measurements. The comparison with threshold-loudness-balance measurements on ten subjects showed no significant differences with a confidence of 95% and coupler measurements showed differences less than 0.8 standard deviations in all cases (i.e., no significant differences with α=0.05). In summary, the one-piece earphone cushion does not differ significantly in acoustical performance from the two-piece MX-41/AR cushion. In addition, there is a strong indication that the one-piece cushion will afford more consistent performances between units, more long-term stability, and better wearer comfort than the conventional MX-41/AR cushion.
Comments on ’’Analysis of a composite compliant baffle’’ [J. Acoust. Soc. Am. 64, 1509–1513 (1978)]
Authors: Gonzalez Manuel A.
Published: October 2005

Errata and addenda to the paper referenced in the title are presented. A discussion of certain limiting conditions for the insertion loss of the baffle against flexural waves is also included.
On the whirling of a base-excited cantilever beam
Authors: Crespo da Silva M. R. M.
Published: October 2005

Whirling (nonplanar) motions of a base-excited cantilever have been recently investigated by Crespo da Silva and Glynn. Some erroneous conclusions, pointed out here, have been reported in this Journal by another author [J. Acoust. Soc. Am. 65, 931–939 (1979)] when reproducing an earlier paper written by Haight and King in 1972 [J. Acoust. Soc. Am. 52, 899–911 (1972)]. The results reported here are confirmed by numerical integration of the nonlinear integro-differential equations of motion.
Detection of signals with identical energy spectra but different waveforms under conditions of signal uncertainty
Authors: Lundeen Conrad , Small Arnold M.
Published: October 2005

Previous research has shown that a signal which may be one of two pure tones will be less detectable than a signal that is of constant, known frequency. In the present study, the effect of waveform uncertainty was evaluated by using pulse-train signals with identical power spectra but different phase spectra. Results for a group of 11 listeners suggest that when differences in the energy spectra of signals are eliminated, signal uncertainty has, at best, a small effect on detection performance.
Synthesizing musical tones from an impulse response stored in a digital memory
Authors: Slaymaker Frank H.
Published: October 2005

By storing a digital representation of the impulse response of an equivalent filter in a digital memory, a set of musical tones can be generated in which every tone in the set has the same spectral envelope rather than the same waveshape as occurs when the waveshape, itself, is stored digitally. When the impulse response is stored, rather than the waveshape, completely arbitrary attack characteristics can be obtained including inharmonic and noise components. The impulse response that is required to synthesize any existing periodic tone, including the attack portion, can be derived by shifting the original tone one pitch period and subtracting the shifted tone from the original.
Effect of a spherical scatterer on the radiation reactance of a transducer at an air–water surface
Authors: Stumpf F. B. , Junit A. M.
Published: October 2005

The radiation reactance of a small magnetostrictive transducer at an air–water surface was measured in the presence of a hollow and then a solid sphere placed in the water. The sphere was placed in the water directly below the transducer and on its radiation axis. Measurements were taken as a function of the sphere’s depth in the water. A measurable effect is observed for depths of two wavelengths or less.
Comments on ’’Energy processing techniques for stress wave emission signals’’ [J. Acoust. Soc. Am. 65, 1556–1561 (1979)]
Authors: Brown J. L.
Published: October 2005

Some observations on Duncan’s theoretical development are made and a shortened alternative analysis presented.
Sonomagnetic pulses from underwater explosions and implosions
Authors: Bird J. F.
Published: October 2005

The magnetic field that is generated by the sound field of a transient acoustic source immersed in electrically conducting fluid in the presence of ambient magnetism is calculated from a recent theory of such ’’sonomagnetic’’ phenomena. A general solution for the sonomagnetic pulse emitted by an arbitrary transient source is derived in terms of the acoustic pressure field directly (as opposed to a less certain source description). For a model pressure pulse, representative of underwater explosion/implosion pulses, the solution is reduced to tabulated functions. The result consists of a sonomagnetic shock plus precursor and relaxation waves, whose properties are discussed analytically and illustrated numerically.
Analytical method to predict noise radiation from vibrating machine systems
Authors: Perreira N. D. , Dubowsky S.
Published: October 2005

A fundamental study of noise generation in high-speed mechanical systems is undertaken. The objective being the development of modeling techniques for the prediction of mechanical system noise levels. Recently developed dynamical procedures are used to obtain the motions of linked mechanical systems with elastic elements and connection clearances. The ranges of critical system parameters are identified and classical acoustical analysis methods are used in determining the most significant acoustic sources. Detailed acoustic models are analytically developed for these significant sources. These methods and models are then used to predict the farfield radiation of a simple, yet representative, mechanical system; an elastic link with connection clearances in a nominal motion container.
Array gain for signals and noise having amplitude and phase fluctuations
Authors: Kleinberg L. I.
Published: October 2005

One of the causes of the deviation of the signal-to-noise array gain from its ideal value is the existence of random amplitude and phase fluctuations of the signal and noise waveforms arriving at the elements of the array. The effect of normally distributed fluctuations on both the signal and noise gains is examined in this paper. An equation is developed which gives the gain, when there are fluctuations, as a function of the ideal gain for both the signal and noise. The expressions for the signal and noise gains used in this paper are valid for all single-frequency fluctuations arising between the source and the point in the array where the output is measured. It is shown that under certain conditions the total signal gain degradation due to fluctuations can be approximated by the sum of the degradation due to fluctuations in the medium and the degradation due to fluctuations in the equipment.
Free-wave propagation through combinations of periodic and disordered systems
Authors: Bansal A. S.
Published: October 2005

A method has been developed for the analysis of free-wave propagation through a combination of two different semi-infinite, monocoupled, periodic systems joined together without or through a finite periodic/disordered system. The general expressions derived from the analysis have subsequently been adapted to study the free flexural wave propagation in beam-type systems. Results have been computed and discussed for different combinations of beam systems which include semi-infinite periodic beams joined (i) through different periodic and disordered finite beams and (ii) without an additional beam at the junction. Attenuation of free waves in such systems, caused by six-span finite beam disorders, has been studied and compared to the attenuation of free waves in an infinite periodic beam and when one of its elements is different from the rest. Although multispan finite beam disorders generally attenuate the propagating incident waves, at certain discrete frequencies they offer no obstruction to such waves. The conditions under which this can happen have been identified and explained. It has been pointed out what type of finite disordered beams can be employed to prevent vibrational energy from flowing from one periodic system to another. The energy flow through the combined system, as governed by the transmitted free wave, has been discussed. The conditions have been explained under which two interacting attenuating flexural waves can transmit energy, although they are incapable of doing so individually.
Multiple scattering of elastic waves by bounded obstacles
Authors: Boström Anders
Published: October 2005

The transition matrix method for stationary elastic waves is extended to a great class of obstacles characterized by piecewise constant properties. First, the translation properties of the basis functions is used to treat two and, then, several homogeneous obstacles, and thereafter an obstacle with consecutively enclosing layers is considered. It is then indicated how these two basic methods of combination can be applied to treat more complex cases, including an obstacle consisting of several nonenclosing parts. Finally, we give some numerical applications to configurations of spherical and nonspherical obstacles in and below the resonance region.
Acoustic propagation in aperiodic transition layers and waveguides
Authors: Canévet Georges
Published: October 2005

Wave propagation in inhomogeneous media is studied by a new method, the ’’cutting-out’’ Jessel’s method. Emphasis is on transition layers, where both the sound velocity and density variations are taken into account. Several classes of layers are studied and impedance matching by a smooth dioptre is described. By using the analogy between inhomogeneous media and waveguides, this property of impedance matching has been extended to connecting horns, thus leading to the definition of a new family : the aperiodic horns.
Transient scattering of a piezoelectric wave from a crack
Authors: Sabbagh Harold A.
Published: October 2005

The problem of the scattering of transient antiplane shear electroelastic waves from a crack in a piezoelectric medium possessing 6-mm symmetry is solved by determining the electric dipole density induced on the crack by the incident wave. An integral equation satisfied by the Laplace-transformed dipole distribution is derived by appealing to the piezoelectric reciprocity relation. The solution of the integral equation is accomplished by expanding the dipole distribution in a series of first-order spline functions with unknown coefficients and then applying the method of moments to transform the problem to a vector-matrix one, which is readily handled by a computer. Inversion back into the time domain is effected by an efficient numerical method of inverting Laplace transforms. Results are given for the cases of normal and oblique incidence of the wave onto the crack.
Scattering of a plane wave by a Schroeder diffusor: A mode-matching approach
Authors: Strube Hans Werner
Published: October 2005

The two-dimensional, scalar diffraction theory is developed for a diffusing surface as suggested by Schroeder, consisting of an array of ’’wells’’ of equal widths but different depths, separated by hard, thin walls. Diffusors of finite size as well as infinite, periodic ones are treated. Matching the plane waves in the free half-space to the wave modes in the wells yields an infinite but discrete linear equation system in either case. For a periodic diffusor based on a quadratic-residue (QR) sequence, numerical results are compared with measurements on a finite diffusor comprising two periods. The results are also compared with those obtained by approximating the diffusor as a locally reacting surface. The differences are, at most, a few decibels; the mode-matching results are usually closer to the measurements. The uniformity of scattering is tested over a range of wavelengths of 1:4; QR sequences are superior to pseudorandom sequences.
Diffraction by a planar, locally reacting, scattering surface
Authors: Strube Hans Werner
Published: October 2005

The integral equation for the diffraction of a plane scalar wave by a locally reacting, planar, finite scattering surface is treated, the surrounding being either a free space or a uniform locally reacting plane. The surface is described by a ’’generalized reflectivity’’—a bilinear function of the reflection factor containing two free parameters. By proper choice, the validity of Kirchhoff’s Fourier approximation of the diffraction pattern can be extended. Also the analytical treatment of some simple scattering and inverse scattering problems is alleviated. Numerical solution methods are then considered; apart from the direct method, only applicable to small equation systems, an iteration procedure is developed, based on Neumann’s successive-approximation method. Proper choice of the two free parameters leads to fast convergence in most cases. The methods are tested with Schroeder’s quadratic-residue-sequence diffusors. Agreement with the measurements is acceptable but not perfect.
Backscattering of short ultrasonic pulses by solid elastic cylinders at large k
a
Authors: Welton P. J. , de Billy M. , Hayman A. , Quentin G.
Published: October 2005

Backscattering measurements from solid brass, aluminum, and lucite cylinders in water have been performed at a ka of approximately 240 using short acoustic pulses. Numerous discrete echoes are received due to multiple internal reflections of the acoustic pulse at the boundary of the cylinders. Excellent agreement between the measured echo arrival times and the echo arrival times predicted by the theory of Brill and Überall [J. Acoust. Soc. Am. 50, 921 (1979)] is obtained for all of the cylinders. The amplitudes of the backscattered echoes from the brass and aluminum cylinders are also compared with theory and fair agreement is obtained.
Combining acoustic holography with space-frequency equivalence
Authors: Kock Winston E.
Published: October 2005

Space-frequency equivalence, a 1958 concept involving either electromagnetic or acoustic detection systems, states that the physical complexity of a system is interchangeable with the frequency complexity of the system so that the use of a multiplicity of discrete frequencies permits a significant reduction in the physical (space) extent of the system. The implications of combining this equivalence with holography are here examined.
Fourier efficiency using analytic translation and Hilbert samples
Authors: Williams Jack R.
Published: October 2005

The discrete Fourier transform (DFT) inherently accepts complex data; yet signals to be processed are usually real. This necessitates special accommodations if efficient computation is to be achieved. Further accommodation is necessary for efficiency when processing bandpass data. Both accommodations can be made by generating analytic signals using Hilbert transforms. The generation of such signals around zero frequency can be accomplished by analytic band translation where the bandpass can afterwards be defined at baseband by a pair of matched filters. After baseband processing, the spectrum can be translated back up to an arbitrary frequency or can enter after Hilbert sampling directly into the complex DFT for the most efficient spectrum analysis. The analytic translation to the zero-centered baseband frequencies provides the most conveniently normalized spectrum and facilitates the most efficient use of computational resources. The analytic band translator applies to either digital or analog implementation and is useful in both spectrum analysis and other processes.
Some effects of different maskers on psychophysical performance in discrimination and detection tasks
Authors: Abbas Paul J. , Dalzell Larry E.
Published: October 2005

Psychophysical performance was measured in a number of different tasks in order to compare performance under different masking conditions. With the noise masker set to provide a given amount of masking, frequency discrimination of a 4-kHz tone was shown to be worse in a lowpass noise than in a wideband noise. Discrimination of the intensity of the tone under these two masking conditions was comparable except at the lowest level of tone. Finally, the growth of detectability with level was measured in a detection task, with a greater slope being found in lowpass noise than in wideband noise. The results are discussed in light of the differences in physiological responses observed under similar masking conditions.
Loudness enhancement and decrement in four paradigms
Authors: Elmasian Robert , Galambos Robert , Bernheim Armand
Published: October 2005

When one tone burst (the conditioner) preceeds another (the target) by 100 ms, target loudness is enhanced if the conditioner is more intense and decreased if it is less intense. We show here that similar loudness enhancements and decrements occur when the conditioner follows the target. In all instances, monaural loudness enhancements (in which the conditioner and target are delivered to the same ear) are greater than the dichotic enhancements (in which the conditioner is presented contralaterally), but the decrements, which are smaller than the enhancements, are similar in magnitude. Loudness enhancements and decrements are similar to sequential loudness effects and central tendency effects; the major difference is the relatively very large increases in loudness obtainable in loudness enhancement experiments. We outline a mechanism to account for these loudness phenomena and suggest that this mechanism is responsible for similar perceptual effects that occur in other stimulus dimensions and modalities.
Software for a cascade/parallel formant synthesizer
Authors: Klatt Dennis H.
Published: October 2005

A software formant synthesizer is described that can generate synthetic speech using a laboratory digital computer. A flexible synthesizer configuration permits the synthesis of sonorants by either a cascade or parallel connection of digital resonators, but frication spectra must be synthesized by a set of resonators connected in parallel. A control program lets the user specify variable control parameter data, such as formant frequencies as a function of time, as a sequence of 〈time, value〉 points. The synthesizer design is described and motivated in Secs. I–III, and fortran listings for the synthesizer and control program are provided in an appendix. Computer requirements and necessary support software are described in Sec. IV. Strategies for the imitation of any speech utterance are described in Sec. V, and suggested values of control parameters for the synthesis of many English sounds are presented in tabular form.
Sound propagation through parallel jets exhausting from ducts
Authors: Ting Lu
Published: October 2005

The method of matched asymptotic expansions is employed to construct the solution for the propagation of sound through parallel jets which exit from long ducts and are surrounded by a uniform parallel stream. Parts of the duct walls are lined with acoustically absorbent material. The small parameter for the expansion is the ratio of the inner jet thickness to the acoustic wavelength. The problem is further simplified when we impose the condition that the speed of the outer stream, which accounts for the forward motion speed of the ducts, is much smaller than the speeds of the jets. This condition is valid during landing and takeoff operations. Farfield pressure distributions are obtained for the case in which the inner jet is much faster than the outer jet and the case in which the two jets are the same.
Crossing rate statistics for finite bandwidth or modulated multipath signals
Authors: Mikhalevsky Peter N.
Published: October 2005

In a previous paper [P. N. Mikhalevsky, J. Acoust. Soc. Am. 66, 751–762 (1979)] the first-order statistics of finite bandwidth and/or modulated multipath acoustic signals are investigated. In this paper the crossing rate statistics of such signals are analyzed. It is shown that source bandwidth and modulation increase the phase crossing rate while leaving the amplitude crossing rate unchanged. Data acquired by the Woods Hole Oceanographic Institution and data from the CASE experiment conducted in the Pacific in 1973 are compared with theoretical predictions with very favorable results. The Woods Hole data were previously analyzed [I. Dyer and G. W. Shepard, J. Acoust. Soc. Am. 61, 937–942 (1977)]. Their consistent overprediction of the ratio of amplitude to phase crossing rates is explained when modulation effects are accounted for.
Fiber optic pressure sensor
Authors: Fields J. N. , Asawa C. K. , Ramer O. G. , Barnoski M. K.
Published: October 2005

We propose a new transduction mechanism for fiber optic pressure sensing: pressure-induced microbending, which produces excess optical attenuation in the fiber. A simple bending transducer has been used to determine the response of a step-index multimode fiber to changes in applied pressure. The potential (low frequency) acoustic sensitivity of such a transducer, calculated from this measured response, is approximately 100 μPa into a 1-Hz detection bandwidth.