bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic analysis and perception of Spanish fricative consonants
Authors: de Manrique Ana María Borzone , Massone María Ignacia
Published: October 2005

This paper examines the acoustic properties of Argentine Spanish fricatives and the spectral cues in recognition of these consonants. It was observed that [s] spectrally peaks around 5000 and 8000 Hz, [ℱ] around 2500 and 5000 Hz, [f] around 1500 and 8500 Hz, [x] around 1000 and 4000 Hz and [ç] around 2000 and 4000 Hz. The perceptual importance of each of these spectral peaks was determined by filtering and synthesis experiments. With regard to the voiced fricatives: [b,x,x,x,x] the analysis showed periodic components with an F1 of similar frequency and a variable F2. Noise components were principally observed in [x]. Voiced fricatives proved to be shorter than voiceless ones. The analysis of fricatives in consonant-vowel syllables suggested that both the friction and vocalic portions may provide relevant acoustic cues. Tape-splicing experiments, designed to test this observation, showed that except for [x] and [x], all Spanish fricatives were accurately identified by the friction portion alone. However, it was also observed that in transitionless syllables the vocalic portion affected the phonetic identification of the friction portion. This phenomenon pointed to the perceptual relevance of the transition in some combinations of fricatives and vowels.
Perceptual assessment of fricative–stop coarticulation
Authors: Repp Bruno H. , Mann Virginia A.
Published: October 2005

The perceptual dependence of stop consonants on preceding fricatives [Mann and Repp, J. Acoust. Soc. Am. 69, 548–558 (1981)] was further investigated in two experiments employing both natural and synthetic speech. These experiments consistently replicated our original finding that listeners, report velar stops following [s]. In addition, our data confirmed earlier reports that natural fricative noises (excerpted from utterances of [stx], [skx], [ℱtx], and [ℱkx]) contain cues to the following stop consonants; this was revealed in subjects’ identifications of stops from isolated fricative noises and from stimuli consisting of these noises followed by synthetic CV portions drawn from a [tx]–[kx] continuum. However, these cues in the noise portion could not account for the contextual effect of fricative identity ([ℱ] versus [s]) on stop perception (more ’’k’’ responses following [s]). Rather, this effect seems to be related to a coarticulatory influence of a preceding fricative on stop production: Subjects’ responses to excised natural CV portions (with bursts and aspiration removed) were biased towards a relatively more forward place of stop articulation when the CVs had originally been preceded by [s]; and the identification of a preceding ambiguous fricative was biased in the direction of the original fricative context in which a given CV portion had been produced. These findings support an articulatory explanation for the effect of preceding fricatives on stop consonant perception.
Song features and singing heights of American warblers: Maximization or optimization of distance?
Authors: Lemon R. E. , Struger J. , Lechowicz M. J. , Norman R. F.
Published: October 2005

By discriminant analysis we examined the multivariate relationships between quantifiable features of song and the usual rank of singing height in 19 species of warblers (Family Parulidae) resident in New Brunswick, Canada. We found a correlation of higher frequencies with higher singing heights, although the lowest singing group was not different from the second lowest in this respect. Associated with higher frequencies are repeated groupings of two phone types, low numbers of total phone types and fast frequency sweeps in the last phone of the song. Warblers with lower frequencies tend to have more phone types per song. Warblers singing at lowest levels, however, have large numbers of unrepeated phones or alternatively three to five separate phone types repeated in the series in their songs. Overall, the results indicate that in addition to frequency, structural characteristics of the songs are related to singing height. The results are not consistent with the view that warblers are maximizing the distance over which their songs are transmitted since low- frequency sounds should be preferred on an acoustical basis at most singing heights, if not the very lowest. Warblers may be producing songs which by their frequency and structure carry mainly to individuals of biological significance to the singers, probably individuals on adjacent territories. Other possible explanations are also considered.
Surface-wave displacement: Absolute measurements using a capacitive transducer
Authors: Breckenridge Franklin R. , Greenspan Martin
Published: October 2005

We have constructed a capacitive transducer for the absolute measurement of the normal component of surface-wave motion on a flat solid, the direction of travel of the wave being known. The transducer backplate is a cylinder and has cylindrical extensions on each end that act as electrostatic guards to render calculable the sensitivity and capacitance of the transducer. Compliant support elements are incorporated, resulting in negligible mechanical loading to the surface and flat frequency response over the range of 10 kHz to 1 MHz or better. The amplifier noise floor is equivalent to about 4×10−12 m rms with a 5-MHz bandwidth. The upper limit to displacements measurable by this technique has not been established, but is large enough to encompass the range of interest. Estimated uncertainty of the sensitivity determination is less than 5%.
Error analysis of spectral estimates with application to the measurement of acoustic parameters using random sound fields in ducts
Authors: Seybert A. F. , Soenarko Benjamin
Published: October 2005

Several methods have been proposed using multiple-point pressure measurement of random sound fields in ducts to determine acoustic properties of materials and systems. This paper presents an error analysis of the spectral estimates used in these techniques. Expressions for the normal acoustic absorption coefficient and impedance are derived for a random sound field in a duct. Theory is developed to determine the bias and random errors in estimating the spectral density function for plane-wave propagation in the duct. A bivariate stochastic process has been employed to model the acoustic system. Experimental and theoretical calculations show that minimum-bias error can be achieved by using a small bandwidth in estimating the spectra and by locating the microphones close to the sample. Furthermore, random error can be minimized by maintaining a high coherence between microphone signals. This implies that the microphones should have a small spacing. However, high coherence may not be realized when a microphone location coincides with a node point in the sound field.
New probe microphone for investigating the acoustics of the ear
Authors: Lauridsen Ole , Günthersen Carsten
Published: October 2005

A new probe microphone employing a soft tube and a compensation network for the tube response is described. Because of the soft tube, this microphone is especially suited for investigating the acoustics of the outer ear and the ear canal, and some such measurements are given.
Acoustic properties of tungsten–tin composites
Authors: Rokhlin S. , Golan S. , Gefen Y.
Published: October 2005

The acoustic properties of tungsten–tin powder based composites are described. These materials have high values of acoustic impedance and of sound damping and can be used as backing for ultrasonic transducers. The material is simple to fabricate and its properties are rather satisfactorily reproducible.
Detection of long interaural delays for broadband noise
Authors: Warren Richard M. , Bashford James A. , Wrightson John M.
Published: October 2005

While it has been known for some time that interaural delays of broadband noise can be detected from about 10−5 through 10−2 sec, the ability to detect (and estimate accurately) much longer interaural delay periods has not been reported previously. The perceptual characteristics of dichotic delays are described for periods as long as 1 sec, and a general two-stage theory for detection of all interaural delays is proposed.
Early ultrasonic effects upon mammalian CNS structures (chemical synapses)
Authors: Borrelli M. J. , Bailey K. I. , Dunn F.
Published: October 2005

It has been found that ultrasonic effects upon mammalian CNS chemical synapses are among the earliest morphologic changes that occur. This provides a possible explanation for the earlier findings which showed that a functional effect can be recorded almost immediately following certain ultrasonic exposures while no morphological abnormalities were observed with the light microscope.
Comments on impedance tube measurements
Authors: Waterhouse Richard V.
Published: October 2005

The application of a new impedance measuring method to water-filled tubes is discussed. It is shown that source reflections do not invalidate the method, and that valid results can be obtained at frequencies several times higher than that of the first cross mode of the tube.
Vibrations of circular plates with variable profile
Authors: Gelos R. , Ficcadenti G. M. , Grossi R. O. , Laura P. A. A.
Published: October 2005

Galerkin’s variational approach is invoked in analyzing transverse vibrations of circular plates where the thickness varies according to the functional relation h(r) = h0[1+γ(r/a)n] where n is an integer. The displacement function is approximated in terms of simple polynomials which identically satisfy the boundary conditions. The two lowest frequency coefficients of axisymmetric modes are determined in the present paper for several combinations of the governing mechanical parameters.
Free vibration of regular polygonal plates with simply supported edges
Authors: Irie Toshihiro , Yamada Gen , Umesato Kazuo
Published: October 2005

The free vibration of regular polygonal plates with simply supported edges is studied by the dynamical analogy with membranes. A regular polygonal membrane is formed on a rectangular membrane by fixing several segments. With the reaction forces acting on all edges of an actual polygonal membrane regarded as unknown harmonic loads, the stationary response of the membrane to these loads is expressed by the eigenfunctions of the extended rectangular membrane without internal supports. The force distributions along the edges are expanded into Fourier sine series with unknown coefficients, and the homogeneous equations for the coefficients are derived by restraint conditions on the edges. The natural frequencies and the mode shapes of the actual membrane are determined by calculating the eigenvalues and eigenvectors of the equations. The method is applied to an equilateral triangular through a regular decagonal membrane, the natural frequencies and mode shapes are calculated numerically and the effect of the shape of membrane is discussed. The numerical values obtained for polygonal membranes are immediately converted into those of simply supported polygonal plates.
Spatial concentrations of random response in point-excited waveguides
Authors: Smith P. W.
Published: October 2005

A recent modal analysis [J. Appl. Mech. 46, 417 (1979)] shows that a marked spatial concentration of the mean-square response (larger than the spatial average by a factor 4) may exist in a dynamical system excited by a wideband, localized random force. Response is largest near the source. The system has distributed damping and a cutoff frequency below which waves could not freely propagate in an infinite, undamped system; the finite system has large modal density and strong modal overlap near the cutoff frequency. The same system is examined here by a multiple-scattering analysis. It is shown that the spatial concentration, ascribed in the modal analysis to cross correlation between the responses of many modes, is largely described by the direct field (the first term of the scattering series) and is associated with a narrow band of response near the cutoff frequency, where free waves are strongly attenuated. Closed-form analytical approximations are developed in terms of the fundamental dynamical parameters. In a general discussion, it is pointed out that the extent of modal overlap may be an unreliable basis for predictions of spatial concentrations of response, especially in two- or three-dimensional systems or in systems whose dissipation is concentrated on the boundary.
General theory of acoustic propagation through arbitrary fluid media—I. Propagation equations, conditions of the medium, and general dynamical solutions
Authors: Breton J. R. , Middleton David
Published: October 2005

From first principles a general (nonlinear) differential equation is derived, applicable to acoustic propagation in an arbitrary fluid medium. This general dynamical equation is then formally solved exactly, where the medium may include (surface, bottom) boundaries, turbulence, body forces, dissipation, and other physical conditions known to affect propagation. Because the medium is basically stochastic, one must consider in addition the ensemble (or set) of the above dynamical equations, which together constitute the fundamental Langevin (or stochastic) equation governing propagation here. It is then the statistics, namely the moments, probability densities, etc., of the resultant random pressure field, obtained from the corresponding ensemble of dynamical solutions generated here, which represent the ultimately desired solutions of the governing Langevin equation. In the present paper only dynamical solutions are derived; (later, in Parts II and III, stochastic solutions will be obtained from the former). Among the new results obtained in Part I, in addition to the general dynamical solutions, it is shown how the many forms of the ’’wave equation,’’ in past and current usage, are particular approximations of the general dynamical equation derived above, and what specific dynamical conditions must be quantitatively obeyed for the various approximate forms to be valid in applications.
Case study using arrays of infrasonic microphones to detect and locate meteors and meteorites
Authors: Bedard A. J. , Greene Gary E.
Published: October 2005

On 22 April 1975, two infrasonic observatories in Colorado detected acoustic signals related to a fireball sighting. We use the infrasonic data in conjunction with surface and aircraft observations to investigate the signals. We deduce that the acoustic energy originated from an explosive interaction of the object with the atmosphere at an altitude of about 25 km at a distance approximately 250 km from the observatories.
Mixing of normal modes in a range-dependent model ocean
Authors: Thompson Ian J.
Published: October 2005

The problem of calculating the horizontal propagation of sound along a range-dependent underwater channel is solved in a model using an harmonic-oscillator expansion for the vertical pressure distribution. This oscillator basis set is constant for all ranges. The local normal modes at any range may be recovered by a matrix diagonalization, but this is only strictly necessary at the range limits, to define the outgoing boundary conditions. The method is capable of handling arbitrary range dependencies, and is applied to a range of constant gradients to reveal three propagation regimes. Numerical criteria are found for distinguishing the three cases of (i) adiabatic propagation of modes when the channel changes are gradual; (ii) nonadiabadic propagation when the channel shifts significantly within a ray period; and (iii) mode cutoff, when the energy in a mode is largely lost to the basement.
Piezoelectric Rayleigh waves in elastic ferroelectrics
Authors: Pouget J. , Maugin G. A.
Published: October 2005

Following a companion paper devoted to Bleustein–Gulayev surface modes in elastic ferroelectrics, the present paper examines the surface-wave problem associated with the surface propagation of the remaining components of the elastic displacement and the dynamical polarization. This study yields the notion of strongly dispersive piezoelectric Rayleigh waves in ferroelectrics, which results from an interaction between a classical Rayleigh mode and a ferroelectric mode in the form of a unilateral repulsion of dispersion curves by means of the piezomagnetic coupling induced during the symmetry breaking caused by the bias polarization field. This theory is applied to the case of barium titanate and the behavior of the various amplitudes with depth in the semi-infinite space is exhibited with the allied second-order and boundary-layer effects.
Complementarity of the Reddi method of source direction estimation with those of Pisarenko and Cantoni and Godara. I.
Authors: Bordelon Derrill J.
Published: October 2005

It is shown that the methods of plane-wave signal direction estimation of (a) Reddi, (b) Pisarenko, and (c) Cantoni and Godara (CG), in the case of a nonsingular signal source covariance matrix P, constitute orthogonal projection of the candidate signal direction vectors onto the right eigenspace corresponding to the eigenvalue σ2 of the complex covariance matrix R. Case (a) centralizes on the subspace spanned by the right eigenvectors of R corresponding to eigenvalues larger than σ2, whereas cases (b) and (c) to the orthogonal complement of this subspace being the subspace (right eigenspace) spanned by the right eigenvectors of R corresponding to smallest eigenvalues equal to σ2. It is indicated that Reddi’s and CG’s approach, when restriction is made in the case of CG to equispaced collinear arrays of sensors, are noneconomized versions of Pisarenko’s algorithm. A simplistic beamformer is defined herein which, unlike those derived in the work of Reddi, Pisarenko, and Cantoni and Godara, requires calculation of a minimal eigenvalue, σ2, but no eigenvectors. A maximal linearly independent set of column vectors is selected from the received signal covariance matrix, (R−σ2IN), and these are employed to define a simplistic signal (interference) nulling or preserving beamformer. Finally, it is shown that the case of P non-negative definite, viz., P?0, led CG to a flawed conclusion.
Impact of beam steering errors on shifted sideband and phase shift beamforming techniques
Authors: Mucci R. A. , Pridham R. G.
Published: October 2005

The Shifted Sideband Beamformer (SSB) is a digital, time-domain beamformer intended for bandpass applications. Computational efficiency results from the digital processing of the complex envelope of the sensor data at a rate proportional to the bandwidth of the data. In a previous paper, the spatial response of the SSB was examined and compared to that of a conventional bandpass digital beamformer by modeling the beam steering quantization error as a uniformly distributed random variable. This paper examines, in detail, the specific case of a line array of uniformly spaced sensors where beam steering quantization is shown to produce systematic time-delay errors for both the conventional beamformer and SSB implementations. Expressions are presented for predicting the directions of grating side lobes in the spatial response pattern as a result of these errors. Also, the spatial response of the Phase Shift Beamformer (PSB), which is a limiting case of the SSB and intended for narrow-band applications, is examined. The systematic phase errors of the PSB for a planar array are shown to produce errors in the beam pointing direction for frequencies other than band center. Examples demonstrate this effect for the special case of a line array. Finally, it is shown that the SSB can be interpreted as time-domain beamforming with partial beam outputs formed from subclusters of adjacent sensors with a PSB.
Forward masking by sinusoidal and noise maskers
Authors: Weber Daniel L. , Moore Brian C. J.
Published: October 2005

A 2-kHz sinusoid and a narrow-band noise centered at 2 kHz, with the same total power, served as maskers for a 2-kHz sinusoidal signal. We compare the forward masking produced by these two maskers (1) as a function of offset–offset time for 5- and 35-ms signals, (2) as a function of signal duration for a fixed offset–onset time, and (3) as a function of signal duration for a fixed offset–offset time. In all these comparisons, we find that the noise and sinusoid not only produce different amounts of masking for the same experimental condition, but they also show different trends for the same manipulation. The important relations in these results are demonstrated in an additional set of conditions with a 1-kHz signal. In order to account for the differences observed in both experiments, we argue that forward masking is determined by at least two factors. We suggest signal energy as one factor and the presence or absence of differences in quality between masker and signal as another.
Segmenting speech using dynamic programming
Authors: Cohen Jordan R.
Published: October 2005

Speech is modeled as a Markov chain. Scoring is developed to convert observations of the speech signal into estimated probabilities of the locations of segment boundaries. Dynamic programming is then used to compute a most-probable segmentation for the speech. The process automatically adjusts to speakers and incorporates a priori information in a probabilistic and systematic fashion. The performance of the algorithm appears to be state-of-the-art, independent of speaker.
Shifts in phonetic identification with changes in signal presentation level
Authors: Dorman M. F. , Dougherty Karen
Published: October 2005

Identification functions for stimuli from a two-formant [bdg] continuum were assessed at three levels of signal presentation: 55, 70, and 90 dB SPL. At 90 dB the [b] category was narrowed, the [d] category virtually eliminated, and the [g] category greatly enlarged. Since high SPLs can alter the identification functions for these simplified speech signals, caution should be exercised when using stimuli of this nature to compare the speech perception abilities of normal hearing and hearing impaired listeners. If high SPLs, independent of cochlear damage, can alter identification functions, then perceptual experiments may best be conducted at equal SPLs rather than at equal SLs.
Spectral analysis of elastic pulses backscattered from two cylindrical cavities in a solid. Part II
Authors: Sancar Selcuk , Sachse Wolfgang
Published: October 2005

The eigenfunction solutions in Part I for the scattering of plane harmonic waves from two cylindrical cavities in an elastic solid is numerically evaluated for incident wave frequencies ranging from 0–10 MHz, and the power spectrum of the backscattered radial-stress pulse is calculated. These theoretical spectra, computed for a wide range of cavity radii, center-to-center separations, and incidence directions, are analyzed and interpreted. Spectral features are explained by the interference of various reflected and diffracted rays. Experimental backscattering spectra are obtained and compared with the theoretical results. Simple expressions which explain the major details of the spectra are derived for applications to quantitative flaw characterization in ultrasonic nondestructive testing.
Anomalous auditory filter bandwidth derived from direct masking of complex signals
Authors: Horst J. W. , Ritsma R. J.
Published: October 2005

Psychoacoustical thresholds were determined for complex signals (triangular spectral envelope and 2000-Hz center frequency) masked by broadband noise. Variation of the fundamental frequency and of the phase relation between the components had no influence on the masked thresholds, although the temporal envelopes of the complexes were completely different. The bandwidth of the signals was varied by changing the slope of the spectral envelopes. From the dependence of the masked threshold on signal bandwidth the auditory filter bandwidth was estimated to be about 100 Hz at 2000 Hz. Masked thresholds determined for complexes with flat spectral envelope resulted in the same auditory filter bandwidth. These values are extremely narrow compared to the value of about 320 Hz often observed in other measures. It is suggested that the masked thresholds are influenced by temporal interactions.
Pitch of unequal-amplitude dichotic two-tone harmonic complexes
Authors: Houtsma A. J. M.
Published: October 2005

Melodic interval identification experiments are reported for dichotic tone complexes of two successive random harmonics having different intensity ratios. Experimentally obtained confusion matrices are compared with theoretical matrices derived from Goldstein’s optimal processor theory, Wightman’s pattern transformation theory, and a newly formulated analytic pitch theory. Results confirm that at relatively low harmonic numbers, the optimal processor theory provides an excellent description of the empirical data, even for large inter-tone intensity differences, but that for complex tones of higher harmonic order analytic pitch perception plays a significant role. At harmonic numbers higher than about six, none of the examined theories or combinations of theories gives a complete account of empirical data, which underscores the fact that aural processing of complex tones is still not well understood.
Loudness of tone pulses in a free field
Authors: Poulsen Torben
Published: October 2005

Investigations of temporal loudness summation of tone pulses have been performed. The investigations comprised equal loudness determinations between pairs of tone pulses with a duration ratio of 1:2, and threshold determinations of the same tone pulses. Pulse durations ranged from 5 to 640 ms. The frequencies were 500, 1000, and 4000 Hz. All pulses were shaped by means of 1/3 octave filters. For 25 normal hearing observers the investigations were performed at the observer’s threshold, and at 35 and 55 dB SPL. Fitting of the experimental data to a single exponential function yields a time constant (τ) of about 200 ms near and at the threshold, whereas τ is about 100 ms at levels well above threshold. Discrepancies exist, nevertheless, between this single-time-constant model and the experimental data obtained for the pulses of shortest duration. To account for this, a model is proposed comprising a combination of two exponential functions. This yields a short time constant of 5 to 10 ms combined with the longer time constant mentioned above.
Form equivalence of the speech perception in noise (SPIN) test
Authors: Morgan Donald E. , Kamm Candace A. , Velde Therese M.
Published: October 2005

An evaluation was conducted of the equivalence of the ten forms of the Speech Perception in Noise (SPIN) Test with normal hearing subjects. Each subject was tested monaurally on all ten forms. Twenty-five subjects were presented the materials at 80 dB SPL at a signal-to-babble ratio of −1 dB. An additional 25 subjects heard the materials at 30 dB SPL, at a signal-to-babble ratio of +3 dB. The data were analyzed for equivalence using a parallel tests model. A detailed rationale for the application of this model to the equivalence of the SPIN test is presented. The results indicated that a subset of seven lists fits the equivalence model for PH, PL, and difference (PH−PL) scores. Additionally, analysis of list–pair data (combination of companion forms) suggested that all five list–pairs resulted in equivalent performance.
Frequency response of interferometric fiber-optic coil hydrophones
Authors: Jarzynski J. , Hughes R. , Hickman T. R. , Bucaro J. A.
Published: October 2005

The frequency response of interferometric optical fiber hydrophones is examined both theoretically and experimentally. Previous models have considered only either the static pressure or high-frequency (axially constrained) response. In the present study, the acoustic sensitivities of fiber coils (∠5 cm diam, 10–20 m total fiber length) are given for the range 100 Hz to 50 kHz. The observed dependence of the acoustic sensitivity on the sound frequency and coil orientation is explained in terms of an approximate theoretical model. According to this model, the acoustic driving force on the coil is the sum of two terms, a surface pressure and a pressure gradient term, of opposite sign. It is assumed that only the lowest-order radial mode of vibration leads to a net optical phase shift in the coil. The observed peaks in the acoustic sensitivity of the coils are found to be in the vicinity of the resonance frequency for the lowest-order radial mode of the coil.
Electroacoustic properties of piezopolymer microphones
Authors: Lerch R.
Published: October 2005

Some important properties of microphones using polyvinylidenefluoride (PVDF) films are discussed. First, the equivalent two-port-circuit diagrams, which allow the determination of the inner electrical impedance of the electric port, are given. The value of this impedance is important for choosing the optimal input impedance of the pre-amplifier. It is shown that the impedance of junction-FET amplifiers is sufficient for this purpose. MOS-FET input stages should not be used because of their poor noise behavior in the audio band. From the electrical impedance, the noise voltage produced by the piezopolymer membrane is calculated. It follows that the signal-to-noise ratio of piezopolymer microphones is approximately determined by the noise voltage of the pre-amplifier, while the noise contributed by the membrane is neglible. If limited to the telephone band, signal-to-noise ratios of over 70 dB can be reached. For tone bursts with carrier frequencies below the mechanical resonance frequencies of the membrane, the microphones show excellent transient response.
Pulsed transmit/receive response of ultrasonic piezoelectric transducers
Authors: Stepanishen Peter R.
Published: October 2005

A model and approach to evaluate the transmit/receive response of pulsed ultrasonic thickness expander transducers is presented. The approach is based on utilizing the Mason model to account for the transducer’s dynamic response and an impulse response method to account for wideband acoustic nearfield and farfield phenomena. An overall transmit/receive impulse response which relates the electrical input and output of the transducer, including the effects of transducer dynamics and acoustic diffraction, is developed via a block diagram and Fourier transform method. Numerical results are presented for typical piezoelectric transducers. The results illustrate the effects of matching and acoustic diffraction on the receive response of typical transducers. Since the effects on the pulse response of matching and backing the piezoceramic element and/or changing the shape of the radiating surface are readily investigated, the model and approach may be used for design purposes. Furthermore, the model may also be readily combined with various types of signal processors to improve spatial resolution in pulse echo systems via the utilization of coded pulses and/or advanced processing methods.
Comment on the use of Hadamard’s example in ’’Numerical spatial marching techniques in duct acoustics’’ [J. Acoust. Soc. Am. 65, 297–306 (1979)]
Authors: Quinn Dennis W. , Baumeister Kenneth J.
Published: October 2005

This note clears up some possible confusion concerning the numerical solution of an initial value problem for the Helmholtz equation. An example is given which demonstrates that the initial value problem for the Helmholtz equation is ill-posed in the sense that small errors in the initial data lead to large errors in the solution. A stable numerical marching technique for such an ill-posed problem is described as a regularized problem in the sense of Tikhonov.
On the feasibility of using multimode optical fibers in optical hydrophones
Authors: Shajenko Peter
Published: October 2005

Optical hydrophones which use multimode optical fibers offer substantial simplication of acoustic detection systems. The measurements using multimode optical fibers have been found to compare favorably with measured acoustic pressures using piezoelectric sensors.
Reply to comments by D. McFadden
Authors: Linn Roth G. , Kochhar Ravindra K. , Hind Joseph E.
Published: October 2005

Dennis McFadden’s comments [J. Acoust. Soc. Am. 69, 1836–1837 (1981)] are well taken, and we believe there is little disagreement between our views.
Multifrequency echoscopy for quantitative acoustical characterization of living tissues
Authors: Hayakawa Yoshinori , Egawa Jun , Yosioka Katuya , Wagai Toshio
Published: October 2005

A method is proposed, which enables one to extract acoustic tissue parameters quantitatively from the data of multifrequency echoscopy. With three differeent frequencies, influences of frequency dependence of target strength on echo intensity is eliminated by this method and the spatial distribution of the second derivative of attenuation coefficient with respect to the natural logarithm of frequency is obtained. A new type of ultrasound computed tomography is discussed, which may be useful in wide portions of the body where the existence of gas filled organs and bones makes the use of ultrasound transmission computed tomography impossible.
Experimental verification of the impulse response method to evaluate transient acoustic fields
Authors: Stepanishen Peter R. , Fisher George
Published: October 2005

An experimental verification of the impulse-response method to evaluate the transient acoustic field of pulsed ultrasonic radiators is presented. Several piezoelectric disk radiators were constructed for the experiments. Transient pressure measurements were obtained at several field points for pulsed wide bandwidth electrical excitations of the radiators. The pressure data were processed via an iterative deconvolution method to obtain experimental impulse responses. The method ideally eliminates the effects of the dynamic response of the transmit and receive system on the impulse responses. A comparison of the experimental and theoretical impulse responses shows the responses to be in general agreement.
Acoustic cavitation prediction
Authors: Apfel R. E.
Published: October 2005

We have derived an approximate expression for the threshold pressure for transient acoustic cavitation and have used this result with published expressions for the thresholds for gas bubble nucleation and for rectified diffusion in synthesizing cavitation prediction charts for water covering a frequency range from 10 kHz to 2.5 MHz, and for gas saturation percentages 10%, 50%, and 100%. This synthesis, which is applicable to other liquids, may provide guidance about the phenomena associated with acoustic cavitation to those who are either trying to minimize or to optimize its effects.
The influence of wind-induced bubbles on echo integration surveys
Authors: Dalen John , Lo/vik Arne
Published: October 2005

An investigation of attenuation of acoustic energy caused by gas bubbles in the surface layers has been carried out. This was done primarily to study the effect on echo integration of fish abundance when using hull-mounted transducers. Two different approaches have been used. The first examines the variation of the echo intensity from an acoustically stable bottom layer and the second measures the total volume reverberation as a function of depths. The bubble density, size distribution, and the attenuation caused by the bubbles is estimated from the measurements done under different weather conditions. The results show that the acoustic attenuation caused by wind-induced gas bubbles in the surface layers appear at a lower wind force and at a greater magnitude than earlier reported and expected. The attenuation is found to increase rapidly with increasing frequency. The results are also used to find the minimum towing depths of a transducer as a function of the wind speed necessary in order to keep the attenuation due to the bubbles below a given number.
The hybrid algorithm: A solution to acquisition and tracking
Authors: Moura José M. F.
Published: October 2005

The paper discusses a solution for platform location in underwater acoustics. The work is relevant to several fields such as the passive detection and tracking of underwater mobiles, the navigation of platforms relative to bottom-moored sources, the coherent synthesis of acoustic apertures, etc. This paper proposes the design of efficient algorithms that recover position and dynamics information by processing the radiated signature of nonfixed sources. There are conflicting requirements: Global location, e.g., the global recovery of the source/receiver separation, and minimization of the associated computational effort. A compromise is a receiver structure, herein referred to as the hybrid algorithm, that exhibits two basic modes of behavior. In the acquisition mode, the hybrid algorithm is globally observable, but nonrecursive. In the tracking mode, the hybrid algorithm, being recursive, is locally observable. The irregularities of the source path impose a maximum time for the acquisition mode, while the tracking mode is time-limited by the unbounded time behavior of the error variance at the output of the recursive algorithm. For the underwater problem, the paper discusses compromises between these time constraints, as well as the consequences on the error performance of operating the acquisition and tracking modes for longer or shorter periods. It establishes strategies to follow in practical acoustic problems, quantifying the relation between the hybrid algorithm behavior and the parameters characterizing the geometry and the statistical noise environment.
Comparison between the effects of continuous and impact noise on cochlear potentials in guinea pigs
Authors: Salt A. N. , Konishi T. , Cook R. O. , Akay A.
Published: October 2005

Cochlear microphonics (CM), action potentials (AP), and endocochlear potential (EP) were recorded from anesthetized, immobilized guinea pigs during potential (EP) were recorded from anesthetized, immobilized guinea pigs during and following 20 min periods of noise exposure. Changes in cochlear potentials were compared in guinea pigs exposed to continuous broadband noise or mechanically generated impact noise of equal energy content. Over a range of continuous noise levels from 95 to 105 dB SPL it was found that continuous noise produced less suppression of CM and a greater suppression of AP than did impact noise of equal energy. A reduction of EP did not accompany CM suppression with either type of noise exposure. Suppression of CM and AP was also compared in guinea pigs with chronically implanted round window electrodes. In these preparations, AP was suppressed to a similar extent by impact and continuous noise of equal energy, but CM was suppressed to a significantly greater extent by impact noise. The data from both series of experiments indicate that the suppression of cochlear responses is not predicted by an ’’equal energy’’ rule when impact and continuous noise are compared.
Acoustic signals of nonthermal origin from high energy protons in water
Authors: Hunter S. D. , Jones W. V. , Malbrough D. J. , Van Buren A. L. , Liboff A. , Bowen T. , Jones J. J. , Learned J. G. , Bradner H. , Pfeffer L. , March R. , Camerini U.
Published: October 2005

Acoustic pulses generated by the passage of 30-GeV protons through water show evidence for the presence of a nonthermal source. In addition to the bipolar leading-compression signal expected from thermal shock, a tripolar leading-rarefaction component is observed. The component is dominant at 4°C, where the thermal signal should vanish. A space-charge effect may be the source of this component, since other proposed mechanisms leading to tripolar pulses should give a leading-compression signal.
Nonthermal acoustic signals from absorption of a cylindrical laser beam in water
Authors: Hunter S. D. , Jones W. V. , Malbrough D. J.
Published: October 2005

A Q-switched ruby laser has been used to study the generation of acoustic signals in water. The presence of a predominant thermal expansion mechanism is verified by the dependence of the signal amplitude on the ambient temperature. Qualitative agreement with the theory for a cylindrical source is implied by the amplitude dependence on the distance from the source. An additional nonthermal mechanism is evident from the existence of a leading compression, tripolar pulse at 4°C, where the thermal signal must vanish. This pulse may indicate microbubble production by the laser beam.
Dilatational waves in an elastic solid containing lined, gas-filled spherical cavities
Authors: Junger M. C.
Published: October 2005

The real and imaginary wavenumber components describing dilatational wave propagation in a porous medium are computed. The acoustically small cavities are spherical in shape and characterized by a statistical size distribution. They are gas-filled and lined with an elastic shell. It is shown that marked dispersion and resonance-enhanced absorption requires that the Poisson’s ratio of the solid matrix lie between 1/3 and 1/2.
Spectral analysis of elastic pulses backscattered from two cylindrical cavities in a solid. Part I
Authors: Sancar Selcuk , Pao Yih–Hsing
Published: October 2005

A series solution for the scattering of plane harmonic pressure waves from two cylindrical cavities in an elastic solid is derived in terms of cylindrical wavefunctions. The scattered waves are expressed as an infinite sum of various orders of scattering, the first order being the scattering of the incident wave by each of the two cavities, and each successive order being expressed in terms of the single cylinder scattering coefficients. The exact steady-state solution for the scattered radial stress is derived, which is also the power spectra of the scattered pulse due to an incident pulse of delta function in time. These results are simplified further for the case of backscattering at farfields.
Software synthesizer for phonetic research
Authors: Mattingly I. G. , Pollock S. , Levas A. , Scully W. , Levitt A.
Published: October 2005

SYNTH is a rather conventional software serial two-branch formant synthesizer, employing techniques developed by Rabiner, Rothenberg, and others. We have tried to make its control as convenient and its operation as transparent as possible for the phonetic researcher. The vowel branch, excited by noise and/or a glottal waveform, has three variable and two fixed poles, and optionally, a variable zero (for lateral sounds) or zero and pole (for nasalized sounds). The consonant branch, excited by noise that can be modulated according to the glottal output (for voiced fricatives), has a variable zero and pole. Transfer-function polynomial coefficients are calculated pitch-synchronously. All routines are programmed (for the PDP 11/45) in FORTRAN—IV Plus, except for a few computationally intensive functions coded in assembly language. Fixed parameter values are collected in one modifiable file. SYNTH is called by an executive program (SYN) that also enables editing, storage, and graphic and numerical display of variable and fixed parameter values and output PCM waveforms. [Supported by NSF and VA.]
Dichotic listening reconsidered as a type of masking paradigm
Authors: Lauter Judith L.
Published: October 2005

In most dichotic experiments, sounds played to each ear are drawn from the same set, i.e., masking signals are drawn from the same catalog as the target signals. We wish to consider the possibility of using maskers that are not identical to the target sound set. We have tested the influence of a series of maskers on identification of tonal patterns, with masker presented simultaneously and contralaterally to the target signal. Maskers were designed to sample the range from performance with monaural presentation (i.e., no masker) to performance in the situation where masker catalog is the same as target catalog (the traditional “dichotic listening” arrangement). Maskers studied included: Noise or tone gated on and off with the target, sounds mimicking the temporal fine structure of the target, etc. We have found that: (1) Such maskers can be used to reveal ear differences of the magnitudes found in more traditional dichotic designs, and (2) manipulation of the physical characteristics of the masker may prove a means of studying the psychoacoustical dimensions of some types of complex sounds. [Work supported by NINCDS NS 03856.]
Duration distinguishes tenses in Montreal French
Authors: Santerre L.
Published: October 2005

In rapid connected speech, we observe that the forms of three tenses may be reduced to the same segmental string, for example [teta]; [tetapo]: (1) T'es à Pau (you're in Pau)—Pau is a town of France; (2) T'étais à Pau (you were in Pau); (3) T'as été à Pau (you've been in Pau or you went to Pau). Sonagraphic analysis of the production of five Montrealers asked to say [tetapo] with the intention of meaning the different tenses reveals that both intonation and duration, and, to a certain extent, intensity, as well as the vocalic spectrums, vary with the tense on the three syllables. In order to determine whether the variation of the duration alone is sufficient to distinguish the three tenses, three sentences /tetapo/ were synthesized by means of the Klatt programs at MIT. Tests were done with two groups of Montreal-French listeners (n = 24 and 103), and it was found that they were able to distinguish the three tenses on the basis of the variation of duration on the syllables, P = 1. [Work supported by CRSHC.]
The effect of real time F2 emphasis on speech discrimination in noise
Authors: Arcos John T.
Published: October 2005

This experiment measured the effect of F2 emphasis on discrimination of monosyllabic words masked by noise. The test materials, drawn from the Northwestern Auditory Test No. 6 (T. W. Tillman and R. Carhart, Technical Report SAM-TR-66-55, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas, 1963), were presented in a 70-dB SPL white noise masker. The words were band-pass filtered using a tracking filter that was designed to follow F2. This filter uses a zero-crossing rate in a specific frequency band to set the center frequency of a voltage-controlled band-pass filter. The words were presented at signal-to-noise ratios (S/N) of −8, −4, 0, +4, and +8 dB. Psychometric functions of intelligibility (percent correct) versus S/N were generated for filtered and unfiltered stimuli. Subjects wrote down their responses. The filtered stimuli were about 10% more intelligible than unfiltered stimuli at low S/N, no difference between conditions was obtained at high S/N. These results agree quantitatively with those reported by I. B. Thomas and R. J. Niederjohn, J. Aud. Eng. Soc. 18, 299 (1970). [Work supported by NIH.]
Some measurements of the swimbladder volumes of Chesapeake Bay and Caribbean reef fishes
Authors: O'Keeffe David J. , Harris Gregory S. , Goertner John F. , Peters Greig B. , Wiley Martin L.
Published: October 2005

The importance of the swimbladder in bioacoustic scattering has long been accepted by workers in the field. This paper presents the results of two independent experiments on swimbladder measurements. The first deals with 15 different species in the Chesapeake Bay Region where the measurements were carried out in a manner similar to that of Alexander [R. McN. Alexander, J. Exp. Biol. 36(2), 347–355 (1959)]. The swimbladder volume data from 22 different species of Caribbean reef fishes were taken in the field utilizing calibrated hypodermic needles.