bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfer function method of measuring acoustic intensity in a duct system with flow
Authors: Chung J. Y. , Blaser D. A.
Published: October 2005

A new method of measuring the acoustic intensity of plane waves in a duct with flow is described. In this method, the acoustic transfer function between two locations in the duct is used to determine the acoustic intensity. In the case of no flow, the transfer-function formulation reduces to a cross-spectral relation similar to the relation used to measure acoustic intensity in three dimensions. In contrast to the relation in three dimensions, however, the cross-spectral formulation for a duct is not limited in accuracy by the microphone spacing. The new method has been verified experimentally with a series of laboratory tests. Test results obtained by the transfer function method reveal that the net acoustic power transmitted along the pipe increases as the Mach number increases. The acoustic power radiated from the pipe opening, however, remains unchanged with increasing Mach number. This difference between the transmitted and the radiated power appears to be due to sound absorption caused by vorticity shedding at the pipe opening.
Influence of A-weighting tolerances and frequency-band limits on level measurements
Authors: Wong G. S. K.
Published: October 2005

The influence of type 1 A-weighted tolerances and frequency-band limits on level measurements is investigated theoretically and is verified experimentally. Three A-weighting circuits, each of which satisfied type 1 tolerances, were tested with pulse trains with various crest factors; depending on the frequency-band limits of the measuring system, erroneous level readings could be obtained. For example, at a constant repetition rate of 10 kHz and a crest factor of three, the measured levels obtained with the A-weighting circuits spanned a range of 4 dB when the frequency-band limit was increased from 30 to 100 kHz.
Identification of coarticulated vowels
Authors: Gottfried Terry L. , Strange Winifred
Published: October 2005

Previous explanations of vowel perception held that the most definitive information for vowel identity is the relatively constant formant frequencies in the steady-state portions of vowels. Perceptual studies indicate, however, that vowels spoken in syllables with labial stop consonants are identified more accurately than vowels spoken in isolation. The present study investigated the nature and scope of this consonantal context advantage in the perception of ten American English vowels spoken by adult male and female speakers. Vowels in /p/-vowel-/p/, /b/-vowel-/b/, /k/-vowel-/k/, /k/-vowel, and vowel-/k/ syllables were identified much more accurately than isolated vowels. This is consistent with the hypothesis that dynamic acoustic information due to the coarticulation in syllables is important for vowel identification. Identification of vowels in /g/-vowel-/g/, /g/-vowel, and vowel-/g/ syllables was not better than isolated vowels and was significantly poorer than for other consonantal contexts. Acoustical analyses were performed to determine whether poor production of vowels could account for perceptual errors. Misproduced vowel targets could not account for the overall pattern of identification performance. Phonological factors were also considered but were found to be inadequate to account fully for the results.
Identification of vowels spoken in isolation versus vowels spoken in consonantal context
Authors: Macchi Marian J.
Published: October 2005

Strange et al. [J. Acoust. Soc. Am. 60, 213–224 (1976)] report that naive listeners misidentified approximately three times as many tokens of vowels spoken in isolation as the corresponding vowels spoken in consonantal context. On the basis of these findings, they argue that the superior intelligibility of vowels in consonantal context is due to coarticulatory effects: ’’acoustic information distributed over the temporal course of the syllable is utilized regularly by the listener to identify vowels’’ (p. 213). The present study tested naive listeners’ identification of eleven American English vowels spoken in isolation and in consonantal context with an experimental design comparable to that used by Strange et al. Here, however, listening tests were administered under high quality listening conditions, speakers and listeners were closely matched for regional dialect, and problems with the response alternatives for the vowels were minimized by having listeners identify the isolated vowels and /tVt/ syllables by rhyming them with English words. The results of the tests indicated that isolated vowels could be identified quite well; listeners misidentified only 2% of the vowels when tokens were blocked by speaker and only 8% when tokens were randomized across speakers. Further, the tests did not reveal any overall difference in identifiability between the isolated vowels and vowels in consonantal context.
Acoustically induced turbulence and shock waves under a traveling-wave condition
Authors: Chou K. H. , Lee P. S. , Shaw D. T.
Published: October 2005

Experimental investigations of acoustically induced turbulence and shock waves in a traveling-wave tube are performed with and without the introduction of an air flow through the system. Frequency (f) and intensity (I) effects of the acoustic field are studied using a hot-film anemometer and FFT data processing unit. The effect of the acoustically induced turbulence on a laminar flow is also investigated. Sampled data are first conditioned, then processed to estimate the characteristics of turbulence. It is found that for sound pressure level ≳158 dB turbulence appears. Furthermore, at slightly higher level (∠160 dB) shock waves appear over the range of all frequency. Turbulence measurements were performed over a frequency range of 500–2200 Hz, with intensity over a range of 06.–4.0 W/cm2. Below I=0.6 W/cm2 no turbulent bursts are found. The turbulent spectrum F and the wavenumber k are found to safisfy a power law F∝kα with α?−1.7 to −2.1. The rms turbulent velocity u* is found experimentally to have a I1/2 dependence, yet is relatively insensitive to variation of f. Throughout the whole measuring range of f and I, the rate of energy dissipation per unit mass ε is estimated to be 106–107 cm2/s3. It is also found that superimposing a laminar air stream through the tube will suppress the turbulence.
Bottom interaction of low-frequency acoustic signals at small grazing angles in the deep ocean
Authors: Frisk George V. , Doutt James A. , Hays Earl E.
Published: October 2005

The results of a deep-ocean bottom interaction experiment are presented in which the effects of both bottom refraction and subbottom reflection were observed. Data were obtained in the Hatteras Abyssal Plain using a deep towed 220-Hz pulsed cw source and two receivers anchored near the bottom. For ranges between 1 and 6 km, corresponding to bottom grazing angles less than 13 °, the quadrature components of the received signals were recorded digitally. The observed amplitude shows a strong spatial interference pattern which is composed of the direct and bottom interacting arrivals. It is shown that for small source–receiver separations, the bottom return is dominated by a strong subbottom reflection. With increasing separation, this arrival evolves into a refracted arrival due to the presence of a positive sound-speed gradient in the sediment overlying the subbottom. Because of the gradient, a caustic is formed, and corresponding high intensity regions are observed in the data at the expected ranges. Values of sediment layer thickness, sound-speed gradient, and sound-speed drop at the water–bottom interface are obtained from best fits to the data using ray theory, normal mode theory, and the parabolic equation method. These values are consistent with those obtained in nearby locations by other workers. The success of the parabolic equation method indicates that at small grazing angles, the bottom interaction process may be modeled as a propagation process combined with the effect of a perfect, soft subbottom reflector. A value of sediment attenuation, 0.0015 dB/m at 220 Hz, is also inferred from the data and is among the lowest values reported to date in the literature.
Absorption of acoustic energy by plant leaves
Authors: Martens Maurice J. M. , Michelsen Axel
Published: October 2005

We investigated the vibration of leaves of four plant species in a sound field using a laser-Doppler-vibrometer system. All leaves behave as linear mechanical systems when driven by sound and noise at sound pressure levels (SPL) of up to 100 dB re 20 μPa. The modes of vibration are complex in the investigated frequencies (0.5–5.5 kHz), and change with the orientation of the leaf in the sound field. The vibration velocities of the leaves varied between 10−5 and 3×10−4 m/s, while the vibration velocity of the air particles is 5×10−3 m/s at 100 dB SPL. Although the amount of sound energy absorbed in this way by a single leaf is very small, this mechanism may anyhow contribute to sound attenuation by plants and plant communities, since the number of leaves of one fullgrown tree equals 2×105.
Cross-spectral method of measuring acoustic intensity by correcting phase and gain mismatch errors by microphone calibration
Authors: Krishnappa G.
Published: October 2005

The accuracy of measuring acoustic intensity using two closely spaced microphones is examined. The phase and gain mismatch errors are corrected by measuring the transfer function between the two microphone systems exposing them to the same sound (phase and pressure levels) over a wide range of frequencies. The accuracy of the measurement method was verified by creating a sound field in an anechoic room and by generating plane-wave propagation inside a long length of pipe with an anechoic termination. The measurement accuracies were very satisfactory. This method has the advantage of eliminating the recording and processing of two sets of data required in the circuit switching technique.
Factors in the discrimination of tonal patterns. III. Frequency discrimination with components of well-learned patterns
Authors: Spiegel Murray F. , Watson Charles S.
Published: October 2005

Estimates of the effectiveness of selective auditory attention were obtained by adjusting the level of a target tone, which was presented as one 40-msec component in a ten-tone sequential pattern. When the levels of target and nontarget tones were the same, frequency-discrimination thresholds (Δf/f) following prolonged training varied from 0.01–0.02 for minimal-uncertainty testing conditions to 0.1–0.2 under high trial-to-trial stimulus uncertainty. The functions relating frequency discrimination to target-tone level are widely separated for the two conditions; comparing them, we conclude that the effects of selective auditory attention can be equated to a 50-dB variation in signal level. Patterns that had been well-learned during the minimal-uncertainty testing continued to be discriminated exceedingly well when presented randomly or in a single-stimulus (remembered standard) procedure. The results of these latter experiments are consistent with a ’’top-down’’ processing interpretation in which well-learned patterns are first identified to locate the portions requiring further resolution.
Vowel formant frequency characteristics of preadolescent males and females
Authors: Bennett Suzanne
Published: October 2005

This report describes the vowel formant frequency characteristics (Fl–F4 of five vowels produced in a fixed phonetic context) of 42 seven and eight year old boys and girls and the relationship of vocal tract resonances to several indices of body size. Results showed that the vowel resonances of male children were consistently lower than those of females, and that the extent of the sexual differences varied as a function of formant number an vowel category. Averaged across all measured formants of all five vowels, the overall sexual distinction was approximately 10%. The range of differences extended from about 3% for F1 of /i/ to 16% for Fl of /ae/. Measures of body size were always significantly related to these children’s formant frequencies (range in multiple r’s −0.506 to −0.866). The origin of the sexual differences in vocal tract resonance characteristics is discussed with reference to differences in vocal tract size and articulatory behaviors.
Beam patterns from pulsed ultrasonic transducers using linear systems theory
Authors: Bardsley Brent G. , Christensen Douglas A.
Published: October 2005

In medical ultrasonic imaging the beam pattern of the transducer is important in that it defines the lateral resolution of the system. Although the pulsed mode is generally used in diagnostic imaging due to its ability to provide increased axial resolution, the beam pattern is usually calculated assuming continuous wave (cw) excitation because of the simple Fourier transform relationship between the beam pattern and the aperture function for this case. Unfortunately, as the direction from the main lobe is increased, there is an increased disparity between the cw beam pattern and the pulsed beam pattern which has particular consequence when calculating the grating lobe response of an array. In this paper a method is presented using linear systems theory to analyze the beam patterns from an aperture with pulsed excitation. The frequency spectrum of the pulsed input signal is multiplied by the system transfer function and the beam pattern is obtained by an inverse Fourier transform. It is found that the system transfer function is a frequency scaled version of the cw beam pattern for the aperture. Pulsed beam patterns for both a 2.25-MHz, 2.6-cm uniform aperture and a 16-element array are computed using this method and these are displayed as three-dimensional isometric plots. The reduced grating lobe response of a pulsed array can be explained in both the frequency and time domains.
Model for spatial variability effects on single-path reception of underwater sound at long ranges
Authors: Robertson G. H.
Published: October 2005

A model is described for the spatial energy distribution in a ’’single’’ underwater sound path from which properties of the received signals, such as strength variations and coherence, can be calculated. The principal observation that motivated this realization of a model is that signal strength seems to vary much more rapidly across a path than along it. Since this condition might be caused by alternate focusing and defocusing of the signals along the path, because of forward scattering into small angles by random variations of the refractive index of the medium, the model is constructed on this basis. The model exhibits a composite structure for the single path that consists of needle-like patterns of high intensity aligned in the same direction, but making (probably uncorrelated) fluctuations about this direction. The dimensions and separation of these patterns are calculated, as is the coherence along and perpendicular to the path. Experimental data are used to show that a curve based on the model gives a good fit for a considerable range of the parameters: Frequency, receiver separation, and source distance.
Speech acoustic-cue discrimination abilities of normally developing and language-impaired children
Authors: Tallal Paula , Stark Rachel E.
Published: October 2005

The ability of 35 language impaired (LI) and 38 normally developing children between the ages of 5 and 8 1/2 yr to discriminate between speech stimuli, using an operantly conditioned, nonverbal motor response, was investigated. Six syllable contrasts ([ba] versus [da], [da] versus [ta], [ε] versus [F], [dab] versus [dFb], [sa] versus [sta], and [sa] versus [ℱa]) were selected to investigate discrimination of various temporal and spectral cues. Results demonstrated that the LI group made most errors discriminating syllables which were differentiated by consonants and fewest errors on those differentiated by vowels. The normal group made most errors discriminating between syllables including fricatives and brief vowels and fewest errors on stimuli differentiated by stop consonants or vowels in context. The LI group was significantly poorer than the normals in discriminating all syllables that incorporated brief temporal cues followed rapidly in succession by other acoustic cues. They also were impaired in discriminating [sa] versus [ℱa]. They were unimpaired discriminating stimuli differentiated by vowels. It is suggested that the particular constraints demonstrated by LI children in their nonverbal and speech processing abilities may be attributed to abnormalities in mechanisms involved in auditory masking.
MX41/AR earphone cushions versus a new circumaural mounting
Authors: Lippmann R. P.
Published: October 2005

This letter summarizes the free-field calibration of a new circumaural earphone which uses a standard TDH–39 driver. The results of this calibration indicate that this new earphone is to be preferred over the standard TDH–39 MX41/AR earphone for measurements below 6000 Hz which would ideally be made in free field. To a large extent, it preserves the normal acoustic gain provided by the ear canal and concha in this frequency region. Results also indicate that this new earphone is to be preferred for low-frequency measurements (less than 500 Hz), where its intersubject variability is much less than that obtained with a TDH–39 MX41/AR earphone (2 dB versus 5 to 13 dB).
Scattering of plane waves by a penetrable elliptic cylinder
Authors: Goel G. C. , Jain D. L.
Published: October 2005

We discuss here the problems of scattering of acoustic, electromagnetic, and elastic SH plane waves by a penetrable elliptic cylinder embedded in an infinite medium of different properties. Following usual Green’s function approach, the solution of each problem is reduced to that of two simultaneous Fredholm integral equations of the first kind which are solved when the wave lengths in the two media are large as compared with the distance between the two foci of elliptical coordinate systems. Approximate expressions for the external and internal fields, the farfield scattering amplitude, and the scattering cross section of the elliptic cylinder are derived.
Decoupling approach to modeling perforated tube muffler components
Authors: Jayaraman Krishnamurthy , Yam Kit
Published: October 2005

A transformation is derived to decouple the two differential equations describing one-dimensional acoustic wave propagation in the presence of mean flow, in mufflers with partitioned, perforated tubes. The following analysis leads to compact and exact expressions for the matrix parameters of crossflow elements without any concern for convergence of infinite series or segmental analysis employed in earlier studies. The present analysis is, however, based on assumptions of a uniform perforate impedance on the tube, and of equal mean flow in the two ducts. The predicted transmission loss curves agree very well with published data. The decoupled equations make transparent the connection between high-frequency resonances of perforated elements and the axial propagation of radial velocity fluctuations through the holes, without mean flow. The resonance frequencies of a plug muffler are seen to coincide with resonance frequencies of crossflow elements, which in turn may be correlated very simply and accurately with the dimensionless group (ψl)2 defined in this work. This correlation bears out observed trends with variation of geometric parameters.
Nearfield characteristics of parametric acoustic sources
Authors: Moffett Mark B. , Mellen Robert H.
Published: October 2005

Because it is often impractical to make measurements in the farfield of a parametric acoustic source, it is desirable to be able to predict the farfield from nearfield measurements. A nearfield theory applicable to saturation-limited as well as absorption-limited sources, previously outlined [J. Acoustic. Soc. Am. 63, 1622–1624 (1978)], has been programmed for digital computation. Growth curves for the source level and beamwidth of absorption-limited sources are presented in generalized form. The theoretical results are compared with experimental data from several sources. Sources involving substantial difference-frequency generation in the primary farfield have broader nearfield beam patterns and lower apparent source levels than in the farfield. On the other hand, when most of the generation occurs in the primary nearfield, the pattern is narrower and the apparent source level higher than in the farfield.
Nonlinear third harmonic resonance of flexural waves on a waveguide of thin elastic plate
Authors: Sugimoto Nobumasa , Majima Yoshiyuki
Published: October 2005

The nonlinear third harmonic resonance of flexural waves on a waveguide of a thin elastic plate of infinite length is investigated based on a theory of large deflection of a plate. Two types of waveguide are treated, one having both side edges supported simply and the other having both side edges fixed. Since the nonlinearity in flexural motions of a thin plate is cubic in a deflection, a quasimonochromatic flexural wave and its third harmonic wave can interact resonantly due to the nonlinearity at such a frequency that both waves can propagate simultaneously. The resonance equations for the behavior of two complex wave amplitudes are derived by the method of multiple scales. It is found that, regardless of the edge conditions, the qualitative behavior in each waveguide is governed by the same type of equations. The stationary solutions of the resonance equations show that two wave amplitudes vary periodically to exchange their energy, including solitary waves as limiting cases. Under a special condition, an ’’algebraic solitary wave’’ is also possible.
Mode interactions in an ocean with sound speed a linear function of range
Authors: Williams A. O.
Published: October 2005

Pierce’s method is used to calculate mode interactions in a ’’Pekeris ocean,’’ modified so that the sound speed in the water layer, although independent of depth, changes linearly and slowly with range. This variation causes mutual perturbations of the normal modes. Simplifying restrictions are (a) two dimensions (depth and range), (b) calculations only for the lowest two modes of several, and (c) approximation of the transcendental eigenvalue equation by an algebraic form. Dissipative effects are neglected. Analytical expressions are derived for the interaction contributions of mode 2 to mode 1 and of mode 1 to mode 2. In first-order perturbation, all contributions to any one mode are additive. Each interaction produces a forward-scattered component and a much weaker back-scattered one. Both are proportional to the gradient of sound speed and, approximately, to H/δ2 (H, water depth; δ, ratio of the density of the bottom material to that of water). The back component is also proportional to λ2/H2 (λ, acoustic wavelength). Results are compared with those of an earlier calculation in which the perturbing influence was a linear variation, with range, of water depth.
Community noise levels in Patras, Greece
Authors: Stathis Theodore C.
Published: October 2005

In the city of Patras (Greece), noise measurements were made for the purposes of determining the present noise-pollution levels and the reaction of the people to them. For the latter purpose, a social survey was conducted with the use of a relevant questionnaire which was applied to 500 citizens. Its results show that noise pollution is ranked second in order after air pollution,and that traffic was the principal noise pollutant. The mean noise levels, in 25 monitoring stations throughout the city, were found to be high and definitely unacceptable. For three representative locations, corresponding to high, medium, and low traffic volume, the various statistical noise descriptors, such as Leq, LNP, Ldn and others, were used, together with the other measurements, to estimate the noise environment of the entire city. The high degree of annoyance of the people is justified by the high values of Leq, LNP, Ldn, and TNI that were found.
Method for obtaining a nearfield inverse scattering solution to the acoustic wave equation
Authors: Silvia Manuel T. , Weglein Arthur B.
Published: October 2005

Since the classic paper by Gelfand and Levitan [Am. Math. Soc. Transl., Ser. 2, 1, 253–304 (1955)], much has been published on the inverse scattering problem. Assuming no bound states, there are several well-known solutions that reconstruct one-dimensional or spherically symmetric potentials from farfield scattering information. Moses [Phys. Rev. 102, 559–567 (1956)] and Newton [Phys. Rev. Lett. 4, 541 (1979)] have generalized these procedures for three-dimensional potentials. In this paper, we show how the work of Moses and Newton can be extended to provide a nearfield inverse scattering solution to the acoustic wave equation. In particular, we describe a procedure for obtaining a nearfield inverse scattering solution when the incident probes are arbitrary, unknown, and not necessarily reproducible.
AP responses in forward-masking paradigms and their relationship to responses of auditory-nerve fibers
Authors: Abbas Paul J. , Gorga Michael P.
Published: October 2005

The amplitude of N1 peak of whole-nerve AP was measured in cats using a tone-burst probe with tonal maskers in a forward-masking paradigm. Experiments examined the effects of masker level, frequency, and duration (Tm), as well as interstimulus interval (Δt). Results are consistent with the interpretation that amplitude of N1 reflects activity of a limited group of fibers with CF near the probe frequency. For single fibers, decrement in discharge rate (relative to an unmasked condition) is dependent upon rate to the masker [Smith, Neurophys. 40 (1977)]. For the AP, decrement in probe-elicited amplitude should reflect the rate to the masker in those fibers excited by the probe. Thus measurements of N1 decrement versus masker frequency and level are similar to single unit rate versus level functions. Since decrement in N1 reflects amount of adaptation, increasing Tm decreases probe response. N1 amplitude as a function of Tm thus resembles PST histograms of nerve fibers. Finally, plots of N1 amplitude as a function of Δt are interpreted as a measure of recovery from adaptation.
Echo phase perception in bat sonar?
Authors: Altes Richard A.
Published: October 2005

The bat Eptesicus fuscus is apparently sensitive to the fine structure of the autocorrelation function of its transmitted pulse. This sensitivity has been interpreted as evidence for phase perception in bats at ultrasonic frequencies. An alternative interpretation of the data, however, does not depend upon phase perception. The observed sensitivity to autocorrelation fine structure can be explained by a process that involves cross correlation of filtered spectrograms. Spectrogram representations are insensitive to a constant phase shift.
Perception of anticipatory coarticulation effects
Authors: Martin James G. , Bunnell H. Timothy
Published: October 2005

Articulatory and acoustic studies have shown that the effects of anticipatory coarticulation may extend across several segments in an utterance. But previous perceptual studies suggest that only the information carried by immediately adjacent segments is used in perception. To show that perception is not so limited, we persuaded ten talkers each to produce 12 sentences (e.g., ’’I say poozee’’) of the form ’’I say /C V1 z V2/’’ in which C was /p, t, k/, V1 was /u, F/, and V2 was /i,◊/. Each /i,◊/ sentence pair was cross spliced by exchanging the final syllable /z V2/ so that coarticulatory information prior to the crosspoint was inappropriate for the final vowel V2 in crossed sentences. Recognition time (RT) for V2 in crossed and intact (as spoken) sentences was obtained from practiced listeners. The results were slower RT in crossed sentences, and amount of interference depended on both V1 and C context. Another experiment varied the location of crosspoints across /C V1/ and found that RT interference increased directly with amount and proximity to target of inappropriate precross acoustics. LPC analysis of the experimental sentences showed pretarget variations in F2 frequency which were jointly dependent on identity of C, V1, and V2. Pretarget F2 variations and C and V1 identity jointly predicted amount of RT interference in crossed sentences. Finally, experiments with pretarget F2 variations in synthetic speech repeated and extended the results with real speech. These studies lead to the conclusion that the perceptual significance of coarticulation is not limited to effects on immediately adjacent segments. Listeners appear to be sensitive to many acoustic effects of the mutual influence among the segments in a sequence.
Deformation of a sound field caused by a manikin
Authors: Weinrich So/ren G.
Published: October 2005

Measurements of the deformation of a sound field by the presence of an anthropometric manikin are described. An approximate point source is placed at a distance of 3 m in front of the manikin at the height of the manikin’s ears. In the horizontal plane at this height the resultant SPL is measured around the head at distances of 1 cm to 2 m, measured from the tip of the nose. The signals were pure tones at 1, 2, 4, 6, 8, and 10 kHz. It was found that the presence of the manikin caused changes in the SPL of the sound field of at most ±2.5 dB at a distance of 1 m from the surface of the manikin. Only over an interval of approximately 20 ° behind the manikin (i.e., opposite the sound source) did the manikin cause much larger changes, up to 9 dB. These changes are caused by destructive interference between sounds coming from opposite sides of the manikin. In front of the manikin, the changes in SPL at this distance are within ±1 dB.
Simple equations for the speed of sound in Neptunian waters
Authors: Coppens Alan B.
Published: October 2005

Two simple equations for the speed of sound in sea waters, down to depths of 4 km, have been obtained as approximations to a more precise equation developed by Lovett. The simpler of the two is valid for all Neptunian waters except the Red Sea, Mediterranean Sea, and Persian Gulf, and agrees with Lovett’s equation to within about 0.1 m/s. The other includes these water masses and is in agreement with Lovett to within about 0.03 m/s. The two equations are well adapted to programmable handheld calculators.
Principal-components analysis for low-redundancy encoding of speech spectra
Authors: Zahorian Stephen A. , Rothenberg Martin
Published: October 2005

The principal-components statistical procedure for data reduction is used to efficiently encode speech power spectra by exploiting the correlations of power spectral amplitudes at various frequencies. Although this data-reduction procedure has been used in several previous studies, little attempt was made to optimize the methods for spectral selection and coding through the use of intelligibility testing. In the present study, principal-components basis vectors were computed from the continuous speech of several male and female speakers using various nonlinear spectral amplitude scales. Speech was synthesized using a combination linear predictive (LP) principal-components vocoder. Of the amplitude scales investigated for use with a principal-components analysis of speech spectra, logarithmic amplitude coding of non-normalized spectra emerged as a slight favorite. Speech synthesized from four principal components was found to be about 80% intelligible using a form of the Diagnostic Rhyme Test for rhyming word pairs and about 95% intelligible for words within a sentence context. Speech synthesized from spectral principal components compared favorably in intelligibility and quality with speech synthesized from a control LP vocoder with the same number of parameters.
Piezoelectric polymer probe for ultrasonic applications
Authors: DeReggi A. S. , Roth S. C. , Kenney J. M. , Edelman S. , Harris G. R.
Published: October 2005

Miniature piezoelectric polymer hydrophones for ultrasonic field characterization in the low megahertz region have been developed and tested. The principal advantages of these devices over conventional hydrophones are their uniform frequency response and minimal perturbation of the field. These characteristics are achieved by rendering a small central region of a thin sheet of the polymer polyvinylidene fluoride locally piezoelectric, and then supporting the sheet in the field by holding it taut in a metal hoop having dimensions larger than the field being probed. Both single elements having diameters less than 1 mm and multielement arrays have been formed on the polymer. Methods of construction, signal amplification, and, in one design, rf shielding are discussed, and data are presented on insertion loss, sensitivity, frequency response, and immunity to rf interference.
Kramers–Kronig relationship between ultrasonic attenuation and phase velocity
Authors: O’Donnell M. , Jaynes E. T. , Miller J. G.
Published: October 2005

Kramers–Kronig relations linking the attenuation and dispersion are presented for a linear acoustic system. These expressions are used as a starting point to derive approximate, nearly local expressions relating the ultrasonic attenuation at a specific frequency to the local frequency derivative of the phase velocity (i.e., dispersion). The validity of these approximate relationships is demonstrated in several acoustic systems exhibiting substantially different physical properties.
Nonlinear vibration of beams in an axial force field
Authors: Parameswaran K. , Varadan T. K. , Prathap G.
Published: October 2005

The nonlinear vibrational characteristics of beams with variable axial restraint at the boundary, and with an axial force applied at any intermediate station of the beam are studied. The behavior of the system at the time of maximum amplitude is determined by the use of successive integration and iteration scheme. Numerical results are presented for a uniform, simply supported beam, for the cases of movable and immovable hinges. For the case of an immovable hinge, the nonlinearity is always of the hardening type. In the case of a movable hinge, for low values of the imposed axial force, the nonlinearity is of the softening type. But, the softening behavior changes to a hardening one when the axial force approaches the value of the buckling load. When the results are particularized for the linear case, the agreement is very good with those available in the literature.
Diffraction of a point source by two impedance covered half-planes
Authors: Naghieh M. , Hayek Sabih I.
Published: October 2005

An analytical solution is given to predict the propagation of noise from a point source to a point receiver over an infinite plane consisting of two half-planes, each covered by a different impedance. The solution is found by the use of function theoretic methods, and is evaluated asymptotically by the method of pole subtraction. It includes a reflected wave, three diffracted (ground) waves, and a surface wave due to each impedance in addition to a direct wave. The reflection coefficient form is different from the plane-wave reflection and it is influenced by the sphericity of the wavefront at the receiver range. However, it reduces to the plane-wave reflection coefficient once the point source position approaches infinity representing an incoming plane wave. Out of the two reflecting waves, only one contributes depending on the position of the receiver. The two surface waves correspond to the two impedance half-planes, generally only one contributes depending on the location of the receiver. If the receiver is close to an impedance plane, it picks up the surface wave emitting from that part of the plane, but it disappears as the receiver moves away from that surface. The diffracted (ground) waves depend on the difference of the impedances of the two half-planes.
Comparison of five models of spherical bubble response in an inviscid compressible liquid
Authors: Lastman G. J. , Wentzell R. A.
Published: October 2005

The response of a spherical bubble in an inviscid compressible liquid is studied for five different bubble models. It is shown that the qualitative behavior of the models is essentially the same, even under intense cavitation conditions. The quantitative behavior is similar, especially for low Mach numbers.
Transition noise—The role of fluctuating displacement thickness
Authors: Lauchle G. C.
Published: October 2005

The role of the fluctuating wall shear stress on the noise generated by incompressible boundary-layer transition was recently analyzed [G. C. Lauchle, J. Acoust. Soc. Am. 67, 158–168 (1980)]. The solutions of that analysis suggest that the shear stress mechanism generates hydrodynamic sound weakly in comparison to the sound generated by a fully developed turbulent boundary-layer flow. Because boundary-layer transition is a very unstable and nonsteady flow, we might expect that other acoustic mechanisms exist. In this paper, we examine one other; namely, that of the fluctuating boundary-layer displacement thickness which is expected to occur as turbulence bursts are created and convected over the surface. The analysis shows that a weak monopole sound source occurs, and at low subsonic flow velocities, this source generates significant acoustic energy. Comparisons of the theoretical predictions with available experimental data support this conclusion.
Thresholds for tones in maskers of various bandwidths and for signals of various bandwidths as a function of signal frequency
Authors: Spiegel Murray F.
Published: October 2005

Critical bandwidth (CB), which represents the narrowest filter the auditory system can achieve, may be estimated directly from either of two experiments. A breakpoint emerges from the threshold function of a pure tone presented with maskers of different bandwidth and from the threshold function of noise signals of different widths masked by wideband noise. The bandwidth at which the knee occurs in either function defines the CB. A ’’conjoint’’ CB estimate can also be obtained by extrapolating noise-signal thresholds to the threshold level of a tone in wideband noise. Compared to other estimation procedures, the conjoint estimate is less affected by the signal’s spectral splatter, the masker’s intensity variability in time, and assumptions about the listening band’s placement.
Production of bite-block vowels: Acoustic equivalence by selective compensation
Authors: Gay Thomas , Lindblom Björn , Lubker James
Published: October 2005

Acoustic and articulatory data are reported for steady state vowels produced both normally and with a bite block. The formant patterns of the bite-block vowels were found to approximate those of the naturally spoken vowels. Measurements derived from lateral view still x-ray films showed that the bite blocks induce drastic articulatory reorganization. Using a mandibular frame of reference, we found that speakers compensated for a large bite block by using supershapes of the tongue and the lips (for [u] and [o]). Comparing the two productions using a maxillary frame of reference, we noted that compensation was maximum at the points of maximum constriction and incomplete or partial at points where the vocal-tract area was large. A computer simulation of our speakers’ compensatory strategy revealed that they behaved optimally according to acoustic theory. These findings suggest that a vowel target is coded neurophysiologically in terms of acoustically significant area-function information, specifically, by information related to cavity configuration at points of maximum constriction.
Phonetic perception: Evidence for context-dependent and context-independent processing
Authors: Miller Joanne L.
Published: October 2005

In a series of experiments a selective adaptation technique was used to examine the dependencies that arise in processing phonetically relevant acoustic information in syllable-initial consonants. The pattern of results, identical across two vowel contexts, indicated that voice-onset-time specifying a voicing contrast and the spectral form of the initial transitions specifying a place of articulation contrast are processed in a mutually dependent fashion. A different pattern was revealed, however, for the processing of the spectral form of the transitions specifying a place contrast and the duration of the transitions specifying a manner contrast. Specifically, the data indicated that transition duration is processed independently of the spectral characteristics of the transitions, even though the processing of the spectral characteristics of the transitions is dependent on their duration. On the basis of these findings, the following conclusions were drawn: First, there are distinct patterns of interaction during speech processing; second, the system does not operate entirely in a context-conditioned fashion; and third, at early stages of processing the speech signal is not treated holistically, but rather undergoes analysis in terms of those acoustic dimensions that provide information about phonetic distinctions.
Two-dimensional analytical model of twin jet shielding
Authors: Gerhold Carl H.
Published: October 2005

Estimation of the impact of jet noise requires analytical modeling not only of the noise source mechanism, but also of the propagation of noise from the source to receiver. One factor which influences the jet noise path is shielding of one jet by another in a twin jet configuration. An analytical model is developed to investigate the shielding phenomenon. The two-dimensional wave equation is solved for a stationary line source impinging upon a cylinder of heated flow. The solution estimates the diffraction and scattering of the incident sound wave by the shielding jet in a plane normal to the jet axis. The frequency dependence of the normalized sound pressure estimated by the model is found to agree in form with empirical data. The azimuthal redistribution of the incident sound shows that, as the frequency of maximum shielding is approached, the scattered sound becomes more highly concentrated into lobes adjacent ot the shielding zone.
Acoustic radiation force on a solid elastic sphere in a spherical wave field
Authors: Hasegawa Takahi , Ochi Masayuki , Matsuzawa Kiichiro
Published: October 2005

The acoustic radiation force on a homogeneous solid sphere placed freely in a spherical sound field in an inviscid fluid is calculated; the effect of the elasticity of the sphere material is studied. Calculated results are presented for a variety of solid spheres in water. Quite distinctive resonance departures from the rigid sphere solution are found.
Propagation of plane, cylindrical, and spherical finite amplitude waves
Authors: Trivett D. H. , Van Buren A. L.
Published: October 2005

A numerical solution to the generalized Burgers’ radial wave equation has been developed; it allows one to calculate stepwise the harmonic content of a finite amplitude wave in the frequency domain for the case of plane, cylindrical, or spherical geometry. The finite amplitude wave may have any initial harmonic content with arbitrary phase, and the absorption coefficient of each harmonic is independently adjustable. Remaining in the frequency domain allows a much larger step than conventional algorithms, which alternate between the time and frequency domains. The algorithm is used to investigate the effect of a large second-harmonic absorption coefficient on saturation suppression and to investigate the farfield behavior of spherical waves.
Three-dimensional model calculations for guinea pig cochlea
Authors: Steele Charles R. , Taber Larry A.
Published: October 2005

The WKB approximation was used for calculations of the pure tone response of a straight box model of the guinea pig cochlea with square scala cross sections and the fluid density and viscosity of water. Only one mode of elastic deformation of the partition was considered, corresponding to a flexible pectinate zone of the basilar membrane (BM) with rigid bony shelf, arches, and spiral ligament. Four distributions of pectinate zone transverse bending stiffness were considered, corresponding to volume compliances: (1) CB, measured by Békésy in the guinea pig post mortem, (2) CB/4, (3) CPL, deduced from Békésy’s point load measurements in a human, with BM thickness inversely proportional to the width and rescaled for the guinea pig, and (4) 10CPL. We also considered various values of the relative longitudinal stiffness of the basilar membrane and the condition of drained or filled scala tympani. When compared to in vivo and post-mortem measurements of the guinea pig, the model results lead to the conjecture that the transverse fibers of the basilar membrane decrease in stiffness with time post mortem, while the ground substance increases in stiffness. Calculations using the compliance CB/4, with the ST drained with zero longitudinal BM stiffness give a response similar in location, peak shape, and phase to the in vivo capacitance probe measurements of Wilson and Johnstone [J. Acoust. Soc. Am. 57, 705–723 (1975)]. Calculations for th ST filled and closed show a BM amplitude similar in location and shape to the spiral ganglion cell threshold curves obtained by Robertson and Johnstone [J. Acoust. Soc. Am. 57, 466–469 (1979)] from abnormal cochleas without outer hair cells. This indicates that the normal peak neural stimulation occurs about 1 mm apical of the BM peak amplitude. Naturally, the discrepancies between the postulated physical model and the cochlea prevent firm conclusions about cochlear function.
Off-frequency listening: Effects on psychoacoustical tuning curves obtained in simultaneous and forward masking
Authors: O’Loughlin B. J. , Moore B. C. J.
Published: October 2005

Off-frequency listening—the use of information in different frequency regions to improve performance in masking tasks—has been reported to influence psychoacoustical tuning curves measured in simultaneous masking. The present experiment was designed to establish whether suppression has an effect on off-frequency listening. Psychoacoustical tuning curves were obtained from three observers in both simultaneous and forward masking, by determining the masker level needed to mask a 2.0-kHz probe as a function of the masker frequency. A probe level of 10 dB SL and narrowband noise maskers were used. After obtaining the conventional tuning curves, a fixed masker, at either 1.8 or 2.2 kHz and 10 dB below the corresponding tuning-curve threshold, was added to limit off-frequency listening. In both simultaneous and forward masking, the branch of the tuning curve opposite the fixed masker was shifted downwards, but to a greater extent in forward masking. The suppression of the probe in tuning curves measured in simultaneous masking appears to constrain off-frequency listening. In forward-masking tuning curves, off-frequency listening has a greater effect, and may explain to a large extent the very sharp tuning which has been found in some studies.
Formant-based representation of auditory similarity among vowel-like sounds
Authors: Bernstein Jared
Published: October 2005

Can the acoustic properties of vowels, in particular, formant frequencies, and formant amplitudes, be scaled so that the auditory relations among vowels are representable by their positions in a formant frequency space? Experiments are described in which carefully selected sets of five-formant vowel-like sounds were presented to listeners. Auditory judgements were elicited sufficient to evaluate the conformity of steady state vowel perception with various algebraic forms. Test results demonstrate that if intervowel distances are organized on a formant-by-formant basis, as for example in the commonly used Euclidean distance metric, no scaling of formant frequencies can possibly reproduce the correct ordinal properties of listeners’ data. In order to model listeners’ responses using a formant-based distance, two factors are required for each formant: Scaled formant amplitude levels must be included in the representation, and the difference of the scaled formant frequencies must be weighted by the formant amplitude levels.