bluuebunny/crossref_metadata_2025 huggingface dataset:
The tight-coupled monopole (TCM) and tight-coupled tandem (TCT) attenuators: Theoretical aspects and experimental attenuation in an air duct
Authors: Hong W. K. W. , Eghtesadi Kh. , Leventhall H. G.
Published: October 2005

Active noise attenuators have been developed for use in an industrial air duct. A theory is presented for calculating the attenuation of tight-coupled attenuators, where the microphone and loudspeaker are in close proximity. Practical and theoretical aspects of a tandem system have been developed, utilizing a cascade of two simple monopole attenuators. A theoretical model suitable for use in the computation of the attenuation from both types of tight-coupled attenuators is presented. The tight-coupled tandem attenuator can provide a minimum attenuation of 20 dB for more than three and one-half octave bands from 30 to 330 Hz. Also, the attenuators could provide significant attenuation in the presence of airflow. The attenuation patterns in front of the attenuator loudspeaker are investigated. Good agreement between the measured attenuation and the computed results validates the proposed theory and the model for the calculation of the attenuation from tight-coupled systems.
The effect of varying the slope of the amplitude-frequency response on the masked speech-reception threshold of sentences
Authors: van Dijkhuizen J. N. , Anema P. C. , Plomp R.
Published: October 2005

Within the framework of a study on the merits of a frequency-dependent automatic gain control in hearing aids, the effect of varying the slope of the amplitude-frequency response on the speech-reception threshold (SRT) for sentences in noise was studied for normal-hearing listeners. Speech and noise were both subjected to the same amplitude-frequency response. In the first experiment, the effect of a constant slope was investigated (20 listeners). Over a range of about −7 to +10 dB/oct, the SRT in noise remained constant. In the second experiment, a single change in the slope of the amplitude-frequency response was introduced halfway through the sentence. The effect of varying the transition time over a range down to 0.125 s appeared to be very small. In the third experiment, the slope varied continuously with range and variation frequency (0.25–2 Hz) as the parameters. The masked SRT increased gradually with variation frequency. The results indicate that the masked SRT for sentences is remarkably resistant to dynamic variations in the slope of the amplitude-frequency response.
Calibration of ear canals for audiometry at high frequencies
Authors: Stevens Kenneth N. , Berkovitz Robert , Kidd Gerald , Green David M.
Published: October 2005

A procedure is described for determining the absolute sound pressure at the inner end of the ear canal when a sound source is coupled to the ear, for frequencies in the range 8–20 kHz. The transducer that generates the sound is coupled to the ear canal through a lossy tube, yielding a source impedance that is approximately matched to the characteristic impedance of the ear canal. A small microphone is located in the coupling tube close to the entrance to the ear canal. Calibration is carried out by measuring the response at this microphone when an impulse is applied at the transducer. To estimate the sound pressure at the medial end of the ear canal, the Fourier transform of this impulse reponse is corrected by an all-pole function in which the poles are estimated from the minima in this Fourier transform. Data on individual ear canals are presented in terms of gain functions relating the sound pressure at the medial end of the ear canal to the sound pressure when the coupling tube is blocked. The average gain function for a group of adult ears increases from 2 to 12 dB over the frequency range 8–20 kHz, in rough agreement with data from ear-canal models. Possible sources of error in the calibration procedure are discussed.
High-frequency audiometric assessment of a young adult population
Authors: Green David M. , Kidd Gerald , Stevens Kenneth N.
Published: October 2005

The hearing thresholds of 37 young adults (18–26 years) were measured at 13 frequencies (8, 9,10,...,20 kHz) using a newly developed high-frequency audiometer. All subjects were screened at 15 dB HL at the low audiometric frequencies, had tympanometry within normal limits, and had no history of significant hearing problems. The audiometer delivers sound from a driver unit to the ear canal through a lossy tube and earpiece providing a source impedance essentially equal to the characteristic impedance of the tube. A small microphone located within the earpiece is used to measure the response of the ear canal when an impulse is applied at the driver unit. From this response, a gain function is calculated relating the equivalent sound-pressure level of the source to the SPL at the medial end of the ear canal. For the subjects tested, this gain function showed a gradual increase from 2 to 12 dB over the frequency range. The standard deviation of the gain function was about 2.5 dB across subjects in the lower frequency region (8–14 kHz) and about 4 dB at the higher frequencies. Cross modes and poor fit of the earpiece to the ear canal prevented accurate calibration for some subjects at the highest frequencies. The average SPL at threshold was 23 dB at 8 kHz, 30 dB at 12 kHz, and 87 dB at 18 kHz. Despite the homogeneous nature of the sample, the younger subjects in the sample had reliably better thresholds than the older subjects. Repeated measurements of threshold over an interval as long as 1 month showed a standard deviation of 2.5 dB at the lower frequencies (8–14 kHz) and 4.5 dB at the higher frequencies.
Measures of phonation type in Hmong
Authors: Huffman Marie K.
Published: October 2005

This study examines measures of glottal flow for vowels of Hmong, a Southeast Asian language which uses breathy and normal phonation contrastively. A software inverse filter was used to recover glottal airflow from oral airflow recordings. Properties of glottal flow measured in the time domain were glottal pulse symmetry and relative closed-phase duration. In the frequency domain, measures of spectral tilt and the amplitude difference between F0 and H2 were applied to discrete Fourier transforms (DFTs) of the glottal flow waveforms. Spectral tilt could not be reliably measured for many tokens. For the other measures, values were available for all tokens and were compared across phonation types. Flow pulse symmetry is not significantly different for breathy and normal-voice vowels. On the other hand, prominence of the fundamental relative to the second harmonic is a very significant correlate of the breathy/normal distinction, as is the relative closed-phase duration. These results are considered in light of an existing model of the voice source.
Piano string excitation III: General solution for a soft narrow hammer
Authors: Hall Donald E.
Published: October 2005

As an important preliminary exercise for understanding excitation of real piano strings, the general solution for a point hammer of mass m hitting a perfectly flexible string of linear density μ is developed further by allowing for hammer compliance. Previous work on this problem is critically reviewed, and the existing analytic theory is summarized. The role of the critical compliance C0=m/16μT is discussed, and inclusion of a resistive force is also considered briefly. In close parallel with our earlier general solution for a hard hammer, the analytic solutions are implemented with a microcomputer to overcome the difficulties of multiple contacts between string and hammer, and representative results obtained by this method are presented. While this approach constitutes a general solution of the problem in principle, it is most practical for moderate values of the ratio of hammer mass to string mass and for C not too close to C0.
Addendum to ‘‘An analytical technique for reducing the influence of edge diffraction in reflection measurements made on thin acoustical panels’’ [J. Acoust. Soc. Am. 8
, 19–27 (1986)]
Authors: Piquette Jean C.
Published: October 2005

Additional reference citations appropriate to the subject paper are provided. These serve to put the diffraction-reduction theorem into better historical perspective. The consistency of the theorem with the results presented in these references also provides further substantiation of the general validity of the theorem for the impenetrable cases.
Radiation from S
H-wave line sources embedded in layered media having rough interfaces
Authors: Lakhtakia Akhlesh , Varadan Vijay K. , Varadan Vasundara V.
Published: October 2005

A method for determining the radiation characteristics of an SH-wave line source embedded in a layered medium having rough interfaces is herein described. The presented technique utilizes the plane-wave spectral decomposition of the relevant fields in the framework of the extended boundary condition method. It is also shown how the equations derived for the general case reduce considerably when the interfaces are periodically rough. Extensions of the problem solved here have been briefly mentioned, and the presented solution technique should find application in several areas involving the propagation of elastic waves.
On the acoustic slow wave in air-filled granular media
Authors: Attenborough Keith
Published: October 2005

The relationship between the slow wave predicted by the rigid-frame limit of the Biot theory propagation in a fluid-saturated poroelastic solid and the modified-fluid wave predicted by classical theory for propagation in a rigid porous solid is examined. An anomalous difference between the two formulations of the viscodynamic operator for noncylindrical pores is exposed and explored. The pore shape factor ratio previously introduced in an extension of the classical approach is redefined. The classical rigid-frame formulation is shown to give good agreement with measured data on air-filled spherical lead shot and sands in the audio-frequency range. Modifications to the Biot viscodynamic operator, and the associated low-frequency/low-permeability approximations, that ensure consistency with the classical formulation, are proposed.
Diffraction of sound by a refracting cylindrical barrier
Authors: Cole John E.
Published: October 2005

The effect of refraction caused by a sound-speed gradient at the surface of a diffracting obstacle is investigated by examining both exact and asymptotic solutions for the sound field behind a rigid cylinder. Depending on the sign of the gradient, the curvature due to refraction over the surface of the obstacle either adds or subtracts from the geometric surface curvature and thereby alters the shadow zone of the obstacle. Results of exact and asymptotic solutions are found to display similar trends. Implications regarding improved acoustic performance of barriers are discussed.
Transverse cusp diffraction catastrophes: Some pertinent wave fronts and a Pearcey approximation to the wave field
Authors: Marston Philip L.
Published: October 2005

Diffraction patterns characteristic of transverse cusps are known to be observable in light reflected from curved surfaces or scattered from liquid drops. It is anticipated that transverse cusps may be produced when high-frequency sound is reflected from (or radiated by) certain curved surfaces or is refracted by inhomogeneities. An explicit description is given of a wave which propagates to produce a transverse cusp; the amplitude in the xy plane is exp[ik(g−ct)] with g=a1x2+a2y2x+a3y2, a2≠0. Propagation of this wave in a homogeneous medium is shown to yield a shear-free transverse cusped caustic which locates a transition in the number of rays which contribute to the amplitude. The Fresnel approximation of the two-dimensional diffraction integral is evaluated. The diffracted wave field is proportional to the Pearcey function P(X,Y) or to P*(X,Y), depending on the sign of a1+(2z)−1, where z is the distance from the xy plane. The real parameters X, Y depend on the aj, z, k, and the transverse coordinates in the observation plane. The stationary-phase points for the diffraction integral are discussed. The problem considered is distinct from that of acoustical longitudinal cusps which unfold along the propagation direction.
Sound propagation within a chemically reacting ideal gas
Authors: Barton J. P.
Published: October 2005

The propagation of a one-dimensional sound wave within a nondiffusive, chemically reacting, ideal gas is considered. The particular case of a dissociating diatomic gas is analyzed, though the general procedure may be applied to more complex gas mixtures. The appropriate dispersion equation is derived from fundamental considerations and expressions for the sound speed and the absorption coefficient as a function of frequency are presented. The low-frequency (equilibrium) and high-frequency (frozen) limits are evaluated. Results are presented for oxygen for temperatures of 2000–6000 K and pressures of 10, 100, and 1000 kPa. The calculations for oxygen indicate that absorption due to chemical reaction can be quite strong, particularly in the high-frequency limit at high temperatures and pressures.
Shear wave effects on propagation to near-bottom and sub-bottom receivers
Authors: Koch Robert A. , Vidmar Paul J.
Published: October 2005

Some effects of shear wave processes in a multilayered ocean bottom are examined. Normal mode theory is used to calculate the stress and displacement components at receivers in and on the bottom. The effects of the seafloor on normal modes are contained in a bottom boundary condition involving the impedance derived from the plane-wave reflection coefficient. Shear wave processes are included when the reflectivity is calculated using a solid description of the bottom. Comparisons of the range dependence of stresses and displacements calculated using fluid and solid descriptions of the seafloor indicate that shear wave processes significantly affect the phase of all acoustic field components, both on and in the bottom. Within the bottom, all acoustic component amplitudes may be 10 dB greater if the solid, instead of the fluid, seafloor description is used. On the seafloor, the only acoustic component amplitude substantially affected by shear wave processes is the vertical displacement, which may be 10 dB smaller for a solid bottom than for a fluid one.
Acoustic resonance scattering by viscoelastic objects
Authors: Ayres V. M. , Gaunaurd G. C.
Published: October 2005

In this paper acoustic scattering from a viscoelastic sphere accurately modeled by means of the Kelvin–Voigt model is studied. The approach based on a single impedance-type or Cauchy boundary condition used in the past to account for losses in the body, is reconciled with the exact approach of viscoelasticity, which accounts for material losses via complex field equations, complex propagation vectors, and a set of three realistic boundary conditions on the surface of the sphere. Using the exact approach of viscoelasticity theory, the effect of viscoelastic losses on the various quantities of interest is determined. The Resonance Scattering Theory (RST) is ideally suited to isolate features of the acoustic spectrum which are dependent upon material composition. In order to use the RST for the combination of a viscoelastic object in a liquid medium, an impedance-matched background is required, and it is developed here for the first time. Subtraction of this background successfully isolates the resonances in the present case. Finally, an exact expression for the specific surface impedance of the sphere, which depends in a complicated way on frequency, on mode order, and on the four parameters controlling the viscoelastic properties of the sphere is derived. The effect of all these quantities on the sonar cross section of the sphere, or on the modal contributions contained within it is studied, and many pertinent results are displayed.
Thermoacoustic radiation of sound by a moving laser source
Authors: Berthelot Yves H. , Busch-Vishniac Ilene J.
Published: October 2005

The generation of sound by a moving laser source is investigated both theoretically and experimentally. The analysis is restricted to sound waves generated exclusively through the thermal mechanism. The model is based on the impulse response of a thermoacoustic source as described in a previous paper [J. Acoust. Soc. Am. 78, 2074–2082 (1985)]. The results presented here include pressure waveforms, directivity patterns, sound level dependence on source velocity, and spreading curves for subsonic, transonic, and supersonic source velocities. In general, experimental results are in good agreement with theoretical predictions.
Resonance theory of elastic waves ultrasonically scattered from an elastic sphere
Authors: Brill D. , Gaunaurd G.
Published: October 2005

The interaction of elastic waves incident on an elastic spherical inhomogeneity is studied in detail, particularly in the resonance scattering regime. Incident and scattered compression and shear waves in lossless elastic media separate into three modes: a p mode for the compression wave, and s and t modes for the shear wave. A description of how the acoustic energy redistributes among these modes during the scattering process is contained in the scattering matrix that we separate here into background and resonance portions for the two extreme cases of a nearly soft and a nearly rigid elastic sphere. This produces farfield scattering amplitudes which are a superposition of a background contribution felt to contain reflected and Franz-type circumferential waves and a resonance contribution that seems to contain refracted, Rayleigh, and whispering gallery waves. Limiting cases (a fluid sphere in an elastic medium, an elastic sphere in a liquid medium, and a fluid sphere in a fluid medium) are extracted from these results to show agreement with previous work. Plots show the background and resonance portions of the scattered amplitudes and their connections with the poles of the scattering amplitude in the complex frequency plane. The methodology of the resonance scattering theory (RST) is summarized with a very general yet basic example of importance in acoustic/ultrasonics and elastodynamics/NDE, which contains all earlier situations.
Frequency discrimination in the mammalian cochlea: Theory versus experiment
Authors: Holmes Mark H.
Published: October 2005

A three-dimensional hydroelastic model for the motion in the cochlea is analyzed for the case of a pure-tone forcing. It is shown to agree well with experiment, including moderate intensity tuning curves and the frequency map, for a variety of mammals. In doing this, the parameters that are needed for each animal are geometric; thus the theory is easy to apply. The analysis also indicates that the fluid viscosity is the dominant dissipation mechanism, at least for moderate to high frequencies.
Temporal gap resolution in listeners with high-frequency sensorineural hearing loss
Authors: Fitzgibbons Peter J. , Gordon-Salant Sandra
Published: October 2005

Temporal gap resolution was measured in five normal-hearing listeners and five cochlear-impaired listeners, whose sensitivity losses were restricted to the frequency regions above 1000 Hz. The stimuli included a broadband noise and three octave band noises centered at 0.5, 1.0, and 4.0 kHz. Results for the normal-hearing subjects agree with previous findings and reveal that gap resolution improves progressively with an increase in signal frequency. Gap resolution in the impaired listeners was significantly poorer than normal for all signals including those that stimulated frequency regions with normal pure-tone sensitivity. Smallest gap thresholds for the impaired listeners were observed with the broadband signal at high levels. This result agrees with data from other experiments and confirms the importance of high-frequency signal audibility in gap detection. The octave band data reveal that resolution deficits can be quite large within restricted frequency regions, even those with minimal sensitivity loss.
Minimum spectral contrast for vowel identification by normal-hearing and hearing-impaired listeners
Authors: Leek Marjorie R. , Dorman Michael F. , Summerfield Quentin
Published: October 2005

To determine the minimum difference in amplitude between spectral peaks and troughs sufficient for vowel identification by normal-hearing and hearing-impaired listeners, four vowel-like complex sounds were created by summing the first 30 harmonics of a 100-Hz tone. The amplitudes of all harmonics were equal, except for two consecutive harmonics located at each of three ‘‘formant’’ locations. The amplitudes of these harmonics were equal and ranged from 1–8 dB more than the remaining components. Normal-hearing listeners achieved greater than 75% accuracy when peak-to-trough differences were 1–2 dB. Normal-hearing listeners who were tested in a noise background sufficient to raise their thresholds to the level of a flat, moderate hearing loss needed a 4-dB difference for identification. Listeners with a moderate, flat hearing loss required a 6- to 7-dB difference for identification. The results suggest, for normal-hearing listeners, that the peak-to-trough amplitude difference required for identification of this set of vowels is very near the threshold for detection of a change in the amplitude spectrum of a complex signal. Hearing-impaired listeners may have difficulty using closely spaced formants for vowel identification due to abnormal smoothing of the internal representation of the spectrum by broadened auditory filters.
Ultrasonic backscatter from bovine tissues: Variation with pathology
Authors: Fei D. Y. , Shung K. K. , Wilson T. M.
Published: October 2005

This is the second in a series of two papers reporting results collected on ultrasonic propagation properties, namely, velocity, attenuation, and backscatter of various mammalian tissues. In the first paper [J. Acoust. Soc. Am. 78, 871 (1985)], the experimental results of five different types of normal bovine tissues were given. In this paper, results obtained for the most common bovine disease in the liver, liver abscess, and in the heart, lymphosarcoma, will be presented. These data show that the ultrasonic properties of tissues with these two types of pathologies are significantly deviated from those of normal tissues, thus providing further evidence that ultrasonic properties may be used as quantitative indicators of a certain disease for diagnostic purposes.
Response dynamics of goldfish saccular fibers: Effects of stimulus frequency and intensity on fibers with different tuning, sensitivity, and spontaneous activity
Authors: Coombs Sheryl , Fay Richard R.
Published: October 2005

The effects of stimulus frequency and intensity on response patterns (PST histograms) to tone burst stimulation were examined in differently tuned saccular fibers of the goldfish. In addition, the sensitivity of these fibers to amplitude-modulated (AM) signals of different carrier frequencies was measured. The response patterns evoked by unmodulated signals were a complex function of tuning, spontaneous activity and sensitivity of the fiber, and the frequency and intensity of the signal. Frequency-dependent response patterns were found in low-frequency fibers with best frequencies (BF) below 200 Hz. Responses in these fibers ranged from tonic to phasic in nonspontaneous fibers and included more complex patterns in spontaneously active fibers, such as suppression of evoked activity below spontaneous levels. Midfrequency fibers (BF=500–600 Hz) showed responses similar to those in low-frequency fibers, but with less dependence on frequency. In contrast, both high-frequency (BF=800–1000 Hz) and wideband, untuned fibers showed frequency-invariant patterns of adaptation. High-frequency fibers were equally sensitive to AM signals at all frequencies tested. The sensitivity of low-frequency fibers to AM, however, increased as a function of carrier frequency and corresponded to the degree of adaptation in response to unmodulated tones. In general, the AM sensitivity of a fiber could be predicted more by its pattern of response to unmodulated signals than by its tuning characteristics.
Comments on the use of physical measures to assess speech intelligibility
Authors: Schmidt-Nielsen A.
Published: October 2005

Research in the use of physical measures to evaluate speech intelligibility is showing promising results, and a device for measuring the speech transmission index has been developed [Technical Notes and Research Briefs, J. Acoust. Soc. Am. 71, 1612 (1982)]. For many important applications of voice testing, the state of the art has not yet reached a point where such a device can be substituted for standard intelligibility tests using listeners. The two major problems are: (1) The standard error of estimate is too large to make reliable comparisons in the range that would be of interest for selecting among competing methods; and (2) it is not clear that any but the simplest adjustments to voice systems that improve the STI also improve intelligibility, or that a change that improves intelligibility necessarily improves the STI.
Bistatic scattering and identification of the resonances of elastic spheroids
Authors: Werby M. F. , Überall H. , Nagl A. , Brown S. H. , Dickey J. W.
Published: October 2005

Resonances appear in the backscattering cross section of elastic objects (interfering with the contribution of specular echoes) when observed as a function of frequency. Only the resonance frequencies and resonance widths can be determined from such an observation, but not the resonance order. For targets of separable geometry, it has been shown both experimentally [G. Maze and J. Ripoche, J. Acoust. Soc. Am. 73, 41 (1983)] and theoretically [M. F. Werby and H. Überall, J. Acoust. Soc. Am. 82, 265 (1987)] that bistatic observations can determine the resonance order after subtraction of the specular background. The method is applied here to bistatic scattering from elastic spheroids, as analyzed by a T-matrix formalism and computer code. Mode mixing takes place now, but it is shown that for moderate aspect ratios (up to 3:1) a dominant mode can still be used to characterize the resonances.
Similarity solution for low Mach number spherical shocks
Authors: McDonald B. E. , Ambrosiano J.
Published: October 2005

A nonlinear progressive wave equation (NPE) describes the evolution of a low Mach number shock wave. The NPE is the nonlinear time domain counterpart of the frequency domain linear parabolic wave equation (PE) for small angle propagation. The NPE in spherical symmetry admits a similarity solution that specifies both the shape of the pulse and the shock strength as a function of range. For finite amplitude spherical waves whether self-similar or not, the theory predicts constancy of an impulse integral corresponding to that of linear theory. For the self-similar waves, theory and available data are in qualitative agreement in the following areas: (1) The shock strength decreases with range as an approximate power law; (2) the temporal behavior of the solution at fixed range is a shock discontinuity followed by a roughly exponential decay; and (3) the effective relaxation time behind the shock is in reasonable agreement with data for slightly more than the first decade in range.
Theoretical and experimental explorations of the Bohlen–Pierce scale
Authors: Mathews Max V. , Pierce John R. , Reeves Alyson , Roberts Linda A.
Published: October 2005

A musical scale based on the 3:5:7:9 tetrachord is described. It has clearly audible harmonic properties that are derived from the harmonies of the tetrachord. In its equal-tempered version, the nine tones of the scale are selected from a set of 13 equal steps, which have a frequency ratio equal to 31/13. The tenth note of the scale, here called the tritave, has a 1:3 frequency ratio with respect to the first note and has a role similar to that of the traditional octave. Both ‘‘major’’ and ‘‘minor’’ chords can be formed from the notes of the scale. Musicians and untrained listeners rated the consonance of all possible triads formed from a 1-tritave range of the equal-tempered chromatic scale. A wide range of consonance ratings was observed, and chords were judged as most dissonant when they had 1-step intervals. A critical bandwidth dissonance model fits the data well. The same subjects rated the consonance of a harmonized passage played in different tunings. Both groups judged the equal-tempered version as most consonant, but only the musicians were influenced by previous exposure to these sounds. Subjects also judged the similarity of chords and their inversions, both for chords from the new scale and for traditional chords. Musicians were influenced by key relationships, inversions, and chord type in their ratings of the traditional chord set but judged the new chords only by pitch height. Untrained listeners relied on pitch height for both chord sets. This suggests that the ability to abstract more complex information depends on training.
On the role of the amplitude of the fricative noise in the perception of place of articulation in voiceless fricative consonants
Authors: Behrens Susan , Blumstein Sheila E.
Published: October 2005

The current study explores the role of the amplitude of the fricative noise in the perception of place of articulation in voiceless fricative consonants. The amplitude of the fricative noise in naturally produced fricative-vowel utterances was varied relative to the vowel and potential changes in perceptual responses were investigated. The amplitude of the fricative noise for [s] and [š] was reduced such that the amplitude of the noise relative to the vowel was similar to [f] and [θ], and, conversely, the amplitude of the fricative noise of [f] and [θ] was increased such that the amplitude of the noise relative to the vowel was similar to [s] and [š]. The fricative noise was presented to listeners in both its vowel context and in isolation. Results indicated that, when the spectral properties of the fricative noise and formant transitions are compatible, the perceptual effects of the amplitude manipulations are relatively small. In contrast to earlier results, the effects of the manipulation of the amplitude of the noise had a small effect on the overall identification of place of articulation, and, when effects emerged, they varied across the different fricative stimuli. Moreover, although decreasing the amplitude of [s] and [š] resulted in an increase in [f] and [θ] responses, increasing the amplitude of [f] and [θ] did not result in an increase in [s] and [š] responses. Implications of these findings for phonetic feature theories are considered.
Perceptual studies on cochlear implant patients with early onset of profound hearing impairment prior to normal development of auditory, speech, and language skills
Authors: Tong Y. C. , Busby P. A. , Clark G. M.
Published: October 2005

Psychophysical studies were conducted on three prelingual and two postlingual cochlear implant patients. Auditory sensations were produced by electrical stimulation of the residual nerve fibers of the auditory nerve by means of a multiple-electrode cochlear implant. The psychophysical performance of the prelinguals was, in general, poorer than that of the postlinguals; prelingual performance was poorer for repetition rate and electrode position identification, gap detection, and durational and numerosity judgments. Improved performance with time, however, was consistently observed for the prelinguals in the above-mentioned psychophysical tasks. There were significant individual differences in the amount of improvement among the three prelinguals. Speech perception studies were also conducted on the three prelingual patients. The speech perception performance of the three prelingual patients was much poorer than that of postlingual patients in general, and was consistent with their poorer psychophysical performance described above.
Analysis of acoustic wave fronts in the atmosphere to profile the temperature and wind with a radio acoustic sounding system
Authors: Takahashi K. , Masuda Y. , Matuura N. , Kato S. , Fukao S. , Tsuda T. , Sato T.
Published: October 2005

Differential equations were introduced to analyze the acoustic wave fronts in the atmosphere. The wave fronts were found to make an ellipsoid whose major principal axis tilts at an angle of about 45° to the leeward. Utilizing this result, a radio acoustic sounding system (RASS) was used to measure the temperature and wind profiles to heights of over 23 km even under strong wind conditions. The profiles agree with those obtained from a radiosonde and a Doppler radar. The discrepancies are only about 0.5 °C in the air temperature and 1 m/s in the wind speed. The experiments show that the analytical result of the acoustic wave fronts is effective not only in the troposphere but also in the stratosphere. The analysis also shows quantitatively that acoustic waves propagate over the horizon to leeward.
Time deconvolution of diffraction effects—Application to calibration and prediction of transducer waveforms
Authors: Cassereau Didier , Guyomar Daniel , Fink Mathias
Published: October 2005

The concept of a radiation coupling function is used to write a transducer response that includes the diffraction losses. This concept leads to easy interpretations of experimental observations. In a second part a method is proposed for removing the diffraction effects from the observed transducer response. A linear system approach is taken to define the transducer output signal in terms of successive convolutions. The proposed method, based on a numerical deconvolution of the radiation filter, leads to an absolute calibration of the transducer impulse response. Deconvolved waveforms are presented for circular and annular arrays. Once the intrinsic transducer response is known, a direct convolution enables the prediction of the output signal for any distance transducer/reflector. Comparisons between predicted and observed transient waveforms are given for circular and annular arrays.
Cavitation and bubble bursting as sources of oceanic ambient noise
Authors: Prosperetti Andrea , Lu Nan Q.
Published: October 2005

Cavitationlike bubble collapses and the bursting of floating bubbles have been proposed in the literature as sources of oceanic ambient noise at kilohertz frequencies. The first process is shown to be physically impossible in the oceanic environment. The noise produced by the second mechanism is estimated and shown to be too weak to be of any significance.
Bubble-related ambient noise in the ocean
Authors: Prosperetti Andrea
Published: October 2005

An analysis is presented of the mechanisms by which bubbles can generate ambient noise in the ocean and the resulting noise levels are estimated. Bubbles can be extremely efficient amplifiers of water turbulence noise up to 100–200 Hz. At higher frequencies, the Lagrangian spectral intensity of the turbulence is too poor for this mechanism to contribute. Above 1–2 kHz, however, the oscillations by which newly formed bubbles dispose of their initial energy is shown to lead to substantial noise levels. This same process cannot account for the noise in the frequency range intermediate between these two because it would require unrealistically large bubbles, with a diameter of 1 cm or more. A possible mechanism active in this intermediate range, in which relatively large levels of ambient noise are observed, is that of collective oscillations of bubble clouds. In all cases the results obtained by the formal derivations (which are based on an adaptation of Lighthill’s theory of aerodynamic noise) are substantiated by simple physical arguments. Other possible noise mechanisms in which bubbles are involved are also briefly considered.
Glottal airflow and transglottal air pressure measurements for male and female speakers in soft, normal, and loud voice
Authors: Holmberg Eva B. , Hillman Robert E. , Perkell Joseph S.
Published: October 2005

Measurements on the inverse filtered airflow waveform (the ‘‘glottal waveform’’) and of estimated average transglottal pressure and glottal airflow were made from noninvasive recordings of productions of syllable sequences in soft, normal, and loud voice for 25 male and 20 female speakers. Statistical analyses showed that with change from normal to loud voice, both males and females produced loud voice with increased pressure, accompanied by increased ac flow and increased maximum airflow declination rate. With change from normal voice, soft voice was produced with decreased pressure, ac flow and maximum airflow declination rate, and increased dc and average flow. Within the loudness conditions, there was no significant male–female difference in air pressure. Several glottal waveform parameters separated males and females in normal and loud voice. The data indicate higher ac flow and higher maximum airflow declination rate for males. In soft voice, the male and female glottal waveforms were more alike, and there was no significant difference in maximum airflow declination rate. The dc flow did not differ significantly between males and females. Possible relevance to biomechanical differences and differences in voice source characteristics between males and females and across loudness conditions is discussed.
Acoustic resonances of thin cylindrical shells and the resonance scattering theory
Authors: Talmant M. , Quentin G. , Rousselot J. L. , Subrahmanyam J. V. , Überall H.
Published: October 2005

An experimental and theoretical study is presented of the properties of circumferential waves on thin-walled elastic, air-filled cylindrical shells immersed in water, and of their excitation by normally incident acoustic pulses of short duration. A spectral decomposition of the multiple echo pulses using the Numrich–de Billy method, and subsequent analysis by the resonance scattering theory (RST), reveal for an aluminum shell the presence of an ℓ=2 wave that can be identified with the S0 Lamb wave on a plate, and of an ℓ=0 wave that at low frequencies corresponds to a water-borne circumferential wave, not given by the Lamb theory of free-plate vibrations but by its extension to a plate with one-sided fluid loading. Calculations of complex pole resonances on aluminum and steel shells, as well as of the corresponding circumferential wave speeds and attenuations, serve to clarify the physical situation.
Nonlinear scattering of crossed ultrasonic beams in the presence of turbulence in water. I: Experiment
Authors: Korman Murray S. , Beyer Robert T.
Published: October 2005

Experiments are reported on the measurements of the scattered sum frequency pressure from two finite-amplitude, mutually perpendicular ultrasonic beams intersecting in the presence of turbulence. In the absence of turbulence, virtually no sum frequency pressure is observed outside the interaction region. The primary carrier beams are generated by individual 2.54-cm-diam transducer units of frequency f1=2.05 and f2=1.95 MHz, respectively. The turbulence is created by a 2.54-cm-diam submerged water jet. The scattering geometry places both of the transmitting acoustic beam axes and the stationary transducer receiving unit axis on the same plane with the jet axis. Angular measurements are performed by rotating the axes of the transmitting crossed beams (which are always perpendicular to each other) in the plane. The highly directional receiver is located outside the interaction region. Scattering angles θ1 and θ2 are measured with vertex at the interaction region from the beam axis of each respective carrier going counterclockwise to the line defined by the beam axis of the receiver. Results for the spectral broadening Δfe and Doppler shift fd of the scattered spectrum as a function of angle for each of the primaries are compared with the sum frequency component. The Doppler shifts of the scattered primaries f (1)d, f (2)d add up to give the Doppler shift of the sum frequency f (+)d at the individual scattering angles. The sum frequency broadening varies with angle as Δf (+)e∝f (+)(σv/c) sin(θ*/2), where θ* is replaced by θ1−45°, σv is an rms turbulent velocity, and f (+) is the average nonlinearly generated sum frequency. Crossed-beam scattering may be valuable as a diagnostic tool in studying turbulent flows.
Numerical evaluation of the statistics of acoustic scattering from a rough surface
Authors: Macaskill C. , Kachoyan B. J.
Published: October 2005

In this article, a formulation is given for two-dimensional scattering of a plane wave incident on an infinitely long surface with a Gaussian distribution of surface height. The surface height may have any physically reasonable correlation function. This method generalizes previous work by the present authors, in which a finite length surface was treated numerically by Fourier methods. For each numerically generated random surface, an integral equation must be solved to find the pressure gradient on the surface. The reflection coefficients, describing the angular distribution of scattered energy, are then formed. It is shown how the various moments of the scattered pressure may be obtained efficiently from averages of these reflection coefficients. Using these techniques, numerical results are presented for the angular distribution of energy for a surface with a Gaussian correlation function of surface height and for a correlation function modeling a more realistic sea surface. Results are presented showing that it is not necessary to taper the incoming wave field in order to obtain accurate answers. For large values of the ratio of the standard deviation of height to the surface correlation length, it is found that the mode of scattering is very different to that found at small surface heights. For some cases, the maximum in the angular distribution is found in the backscatter direction, with the specular peak not at all apparent. It appears that this phenomenon is due to multiple scattering of the acoustic wave at the surface. Finally, it is shown that for the class of problems treated here, the ensemble average intensity is constant at all normal distances from the surface, while the normalized covariance of intensity varies with normal distance from the surface in a way that is, in some limiting cases, very similar to the scattering of a wave passing through a phase modulating screen or an extended random medium.
Ultrasonic transducers for simultaneous generation of longitudinal and shear waves
Authors: Jen Cheng-Kuei , Sreenivas Kondepudy , Sayer Mike
Published: October 2005

Both longitudinal and shear waves can be generated simultaneously and efficiently using 10° rotated Y-cut lithium niobate disks and tilted C-axis zinc oxide thin films. By properly varying the operating frequencies, the ratio between longitudinal and shear excitation strength can be adjusted.
The properties of the estimation error of sound power measurement using sound intensity techniques
Authors: Wu Mei Q. , Crocker Malcolm J.
Published: October 2005

In this article, a general expression was derived for the sound intensity normal to a plane measurement surface caused by a plane distribution of monopole sources. A program was developed to calculate the ratio between the approximate sound power estimated from a finite number of measurements of sound intensity on a plane surface and the exact power passing through the same measurement area. The ratio, which is considered the estimation error of the sound power measurement, is affected by many factors such as the number of measurements, the distance between the source and the measurement surface, the locations of the sources with respect to the measurement points and the types of sources. The effects of these factors on the estimation error were investigated, and some error curves were plotted. By examining the error curves, it was found: (1) when the measurement surface has unit area, the estimation error decreases with an increase in the measurement distance and an increase in the number of sound intensity measurements; and (2) when the measurement surface is a surface enclosing the source, the estimation error depends on the total number of sound intensity measurements over the surface, and does not depend on the measurement distance or the number of measurements over each unit area. Some experimental tests were carried out to check the error curves for the case when the sound source is a monopole. The experimental results agreed well with the theoretical predictions.
Hazard from weapons impulses: Histological and electrophysiological evidence
Authors: Price G. Richard , Kim Hee Nam , Lim David J. , Dunn Derek
Published: October 2005

Current methods of rating the hazard of weapons impulses for the ear have recently been challenged by electrophysiological data from experiments with animal ears which indicate that the hazard from low-frequency impulses is much lower than the hazard from higher frequency impulses (Dancer et al., 1981; Price, 1986b). To supplement these data, histological data are reported here for 51 cats that were exposed on one occasion to either rifle or howitzer impulses at peak pressures from 145 to 155 dB or 153 to 166 dB, respectively. Histological procedures (scanning electron and light microscopy) were carried out over 2 months after the exposure and after electrophysiological measures had been made. For both types of impulse the losses tended to be in the middle of the cochlea in focused lesions, even though the spectral peaks of the acoustic stimuli had been at about 80 Hz (howitzer) and 1000 Hz (rifle). Outer hair cells were more susceptible than the inner hair cells and interindividual differences in effects were large. Furthermore, the two impulse sources were equally hazardous when the peak pressure of the rifle impulse was lower than the peak pressure of the howitzer impulse by about 9 dB. In terms of A-weighted energy, the exposures were equally hazardous when the rifle exposure contained about 35 times less energy than the howitzer exposure. The histological data are thus consistent with the electrophysiological data, which indicate that present standards for impulse noise exposure may overrate the hazard of low-frequency impulses relative to impulses in the midrange.
The effect of atmospheric sound absorption on signal bandwidth and energy and some consequences for bat echolocation
Authors: Hartley David J.
Published: October 2005

The degradation of broadband pulses due to atmospheric absorption was examined as a potential explanation for flexible echolocation behavior. It was found that absorption can explain flexible echolocation behavior in FM/CF bats but not in CF/FM bats. The effects of absorption on target detection and the potential importance to bats of other atmospheric propagation effects are examined and discussed.
Nonlinear and active two-dimensional cochlear models: Time-domain solution
Authors: Diependaal Rob J. , Viergever Max A.
Published: October 2005

A numerical solution method for two-dimensional (2-D) cochlear models in the time domain is presented. The method has particularly been designed for models with a cochlear partition having nonlinear and active mechanical properties. The 2-D cochlear model equations are reformulated as an integral equation for the acceleration of the basilar membrane (BM). This integral equation is discretized with respect to the spatial variable to yield a system of ordinary differential equations in the time variable. To solve this system, the variable step-size, fourth-order Runge–Kutta method described in Diependaal et al. [J. Acoust. Soc. Am. 82, 1655–1666 (1987)] is used. This method is robust and computationally efficient. The incorporation of a simple middle-ear model can be handled by this method. The method can also be extended to models in which the cochlear partition at each point along its length is represented by more than one degree of freedom.
In-plane vibrations of noncircular arcs rigidly clamped at one end and with an intermediate support
Authors: Laura P. A. A. , Rossi R. E. , Verniere de Irassar P. L.
Published: October 2005

The determination of the fundamental frequency of in-plane vibration of the structural system described in this letter is solved using two different approaches: (a) the optimized Rayleigh–Ritz method and (b) a finite element formulation. The effect of a concentrated mass placed at the free end of the arch structure is also taken into account. The agreement of the results obtained following the different methodologies is good for all the situations considered.