bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of temporal sampling strategies for monitoring noise
Authors: DeVor R. E. , Schomer P. D. , Kline W. A. , Neathamer R. D.
Published: October 2005

This paper addresses the problem of the estimation of the long-term (yearly) mean of the Community Noise Equivalent Level (CNEL) or day/night average sound level (LDN). Recent environmental noise standards have emphasized the significance of this problem. While it is possible to continually monitor the noise level, it is not necessarily desirable or practical. It is desirable to sample the level over a relatively short period of time and use this information to draw reliable inferences about the long term mean level. Examination of daily average noise levels (either in mean square pressure or in decibel units) shows that while the data may be stationary with respect to mean level over a several month period, they exhibit a strong pattern of autocorrelation in which positive correlation predominates. As a result, the sample sizes required to achieve a desired level of precision in the sample mean estimate are much larger than they would otherwise be if the data were uncorrelated serially in time. To assess the level of autocorrelation in the data, autoregressive-moving average (ARMA) models are developed for the noise data via the Dynamic Data System (DDS) approach to time series analysis. These models are then used to derive estimates of the sample mean variance and therefore to establish sampling strategies. For the data examined, to obtain an estimate of the mean level within a 5-dB range (±50% of the mean in mean square pressure units), sample sizes in the range of 20–50 consecutive daily averages would be required. If the daily averages were uncorrelated in time, only 5–15 consecutive daily averages would be required. The data used in this study were obtain from continuous monitoring at a number of sites in the vicinity of a busy Naval Air Station. Some data obtained from a large commercial airport were also analyzed and found to have even stronger positive autocorrelation, and therefore requiring even larger sample sizes for mean value estimation.
Performance of children aged 9 to 17 years on a test of speech intelligibility in noise using sentence material with controlled word predictability
Authors: Elliott Lois L.
Published: October 2005

Performance of children aged 9 to 17 years on the SPIN test (Speech Perception in Noise) is described. The 11- and 13-year-olds performed significantly poorer than 15- and 17-year-olds, and this difference occurred primarily for high-predictability sentences presented at a 0-dB signal-to-babble ratio. Performance of nine-year-olds was significantly poorer than performance of 11-year-olds. Possible reasons for these differences are discussed.
Speech synthesis from concept: A method for speech output from information systems
Authors: Young S. J. , Fallside F.
Published: October 2005

A synthesis method, called speech synthesis from concept, is described which has been designed specifically for providing speech output from information systems. It differs from conventional techniques in that data is passed from the information system to the speech synthesis system, not in the form of text or phonetic transcription, but in the form of an abstract structure called an input concept. The speech synthesis from concept system converts an input concept into speech by using a transformational grammar to generate a well-formed English sentence and a word concatenation synthesizer to generate the actual speech output. The ’’top down’’ nature of this process reduces the computation required within the information system and enables high-quality speech to be produced.
Mesoscale variations in the deep sound channel and effects on low frequency and propagation
Authors: Emery William J. , Reid Thomas J. , DeSanto John A. , Baer Ralph N. , Dugan John P.
Published: October 2005

Spatial variability in the deep sound channel is measured in a large-scale oceanographic survey, and its effects on sound propagation are studied in a numerical experiment. The oceanographic data are obtained from a near-synoptic, multiship survey of upper layer thermal structure in the Northwest Pacific which is extended to 4000 m depth using an objective extrapolation model and historical hydrographic data. The extrapolated temperature profiles are converted to salinity and sound velocity profiles using mean temperature-salinity curves, and the resultant sound velocity structure is dominated by mesoscale features which are apparent as large vertical excursions of the channel depth. A numerical experiment that models low-frequency (50 Hz) sound propagation in this model ocean shows that the standard deviation of an ensemble intensity field rises to a plateau of about 5.5 dB in several tens of kilometers, indicating a mesoscale multipath effect with a shorter saturation range than the corresponding internal wave induced effect. Statistics of the intensity at a point receiver are shown to be slightly non-Gaussian, with the non-normal deviation decreasing with depth.
Quadrupole resonance of drops driven by modulated acoustic radiation pressure—Experimental properties
Authors: Marston Philip L. , Apfel Robert E.
Published: October 2005

A new effect of acoustic radiation pressure was detected: the oscillating deformation of mm-radius liquid drops (para-xylene) acoustically levitated in a host liquid (water). A novel method is described for detecting μm amplitude deformations which utilized light scattered by the drop at the scattering angle normally associated with the rainbow. This rainbow photometry technique was used to measure the phase and relative amplitude of steady-state, low-frequency (?100 Hz) deformations induced by a modulated 217.5-kHz acoustic wave. Some of the predictions in ’’Shape oscillation and static deformation of drops and bubbles driven by modulated radiation stresses—Theory’’ [J. Acoust. Soc. Am. 67, 15–26 (1980)] agreed with the measurements. Deformations driven by the radiation pressure could greatly exceed the first-order displacement of the interface. The deformation amplitude varied as the square of the acoustic pressure, and phase had the expected dependence on the modulation frequency when data was normalized according to an experimentally determined damping parameter. The damping, however, was significantly larger than predicted for pure liquids. The interfacial tension inferred from the quadrupole resonance properties was 4% lower than static measurements. The apparatus was also used to levitate superheated drops and the technique may be useful for determining their interfacial tension.
Children’s pure-tone detection
Authors: Elliott Lois L. , Katz Debra R.
Published: October 2005

A three-alternative, forced-choice adaptive procedure, with suitable reinforcement, is appropriate for testing auditory sensitivity in young children. Data obtained using this rigidly specified test protocol support previous findings of reduced auditory sensitivity in young children.
Line integral theory of barrier attenuation in the presence of the ground
Authors: Embleton T. F. W.
Published: October 2005

A theory of diffraction is presented that is based on the line integral along the free edge of a semi-infinite barrier. Expressions, which are not integrable analytically, are given for the cases where the source/receiver line is and is not perpendicular to the edge of the barrier. In this latter case the ’’offset’’ between source and receiver along the barrier enters into the mathematical expression in a more complicated way than hitherto supposed. When the barrier is situated on ground of finite impedance, the amplitude of the sound field is no longer expressible as a single constant that can be taken outside the integrand, but becomes a more complicated function than when the barrier is in free space and involves other parameters such as the source, receiver and barrier heights, and the impedance of the ground. These expressions are suitable for calculating (by numerical integration) the sound field behind a barrier due to the combined effects of direct, reflected, and ground waves in the practical situations where source and receiver are within a few meters of the ground and each several meters from the barrier.
Foliage as a low-pass filter: Experiments with model forests in an anechoic chamber.
Authors: Martens Maurice J. M.
Published: October 2005

In order to investigate the influence of foliage on sound transmission through vegetation, we have examined four model forest situations in an anechoic chamber. In general, we found that the foliage acts in the midfrequencies as a noise amplifier, which is important for the vocalization and communication of animals. In the high frequencies the foliage of plants acts as a good noise filter. The acoustic properties of this filter are determined by the plant species, and depend mainly on the maximum size of the plant organs. A clear correlation is found between the maximum size of the plant leaves and the frequency, from which the filtering capacity of the plants starts. Also, a correlation could be detected between the total biomass of a specific plant species and the noise ’’attenuation’’ in the 1/3-octave bands that are examined. The total noise attenuation caused by the vegetation depends on the spectrum of the noise: the sound pressure level of a noise spectrum with high levels in the high frequencies will be decreased by the plant foliage but the traffic noise spectrum will be changed only in pitch. We conclude that this filtering property of plant communities could be useful in noise abatement.
Propagation of sonic booms in the thermosphere
Authors: Rogers Peter H. , Gardner J. H.
Published: October 2005

A nonlinear theory for the long-range propagation of sonic booms through the thermosphere has been developed. A realistic atmosphere is employed, and consideration is given to such factors as nonlinear stretching and decay of the wave, the effects of the caustic, the linear acoustic attenuation, and the increase in Mach number due to the decreasing density at high altitudes. Detailed results are presented for the case of the Concorde SST in straight, level, and steady flight at 17.5 km and a velocity of Mach 2. We predict maximum ground level pressures of 0.3 Pa with an N-wave ’’period’’ of about 10 s. The sound level is a minimum along the flight track with the maximum signal strength occurring about 300 km off the flight track. The strongest received signal travels initially downward and reflects off the surface of the ocean to the thermosphere. The wave turns around at an altitude of 160 km and is returned back to the ground at a horizontal distance of 320 km from the launch point. The acoustic Mach number of the wave never exceeds 0.2. Ninety percent of the wave’s energy is attenuated below 100 km with 99% attenuated by the time the wave reaches the turning point.
Low-frequency hearing loss: Perception of filtered speech, psychophysical tuning curves, and masking
Authors: Thornton Aaron R. , Abbas Paul J.
Published: October 2005

Four subjects with low-frequency hearing loss were evaluated to determine whether their responses to low-frequency stimulation might be the result of stimulation of nerve fibers with higher characteristic frequencies. Two masking paradigms were employed to indirectly investigate the contribution of high-frequency nerve fibers to the detection of low-frequency stimuli: (1) masking of a low-level, fixed-frequency probe by a variable-frequency pure-tone masker (psychophysical tuning curve) and (2) masking of pure-tones by a high-level, fixed-frequency pure-tone masker. Low-frequency remote masking by tones and displacements in the tips of tuning curves to higher frequencies were interpreted as evidence that low-frequency signals near threshold were being detected by high-frequency fibers in three of the subjects. Three subjects were also tested with high-pass, low-pass, and unfiltered speech both in quiet and in the presence of a high-pass noise masker. Results were interpreted as showing a relatively small contribution of high-frequency fibers to the perception of low-frequency speech.
Nonlinear interaction of two collinear, spherically spreading sound beams
Authors: Tjötta Jacqueline Naze , Tjötta Sigve
Published: October 2005

Nonlinear interaction of two collinear, spherically spreading sound beams is considered and applied to a discussion of parametric acoustic arrays. A general solution is given in the quasilinear approximation in terms of spherical harmonics and used to discuss the asymptotic behavior of the generated sound. Other expansions are also discussed. The main results, however, are obtained by introducing perturbation methods and deriving simplified equations governing the generated sound field, taking into account diffraction, absorption, and nonlinearity. From these equations, solutions are obtained and matched to give a solution valid in the whole space of propagation. Analytical and numerical results are presented and compared with available observations by different authors.
Experiments on the transmission paths and dynamic behavior of engine structure vibration. II. Motoring tests
Authors: Okamura Hideo
Published: October 2005

In order to gain a better understanding of the transmission behavior of the excitation forces in the engine structure, such as the gas forces, the inertia forces, the piston slap forces, and the valve seating impact forces, a series of motoring tests was carried out on a four-cylinder (bore: 86 mm, stroke: 84 mm), in-line, water-cooled high-speed diesel engine. The motoring tests were carried out by changing the combinations of the excitation forces, and at different engine speeds. Under the motoring tests, it could be seen that even the cylinder block bottom sides could be steadily excited by the valve seating impact forces. The transmission behavior of each of the excitation forces can be identified distinctly by the particular frequency components in the power spectral density diagrams of the engine structure responses. Finally, new types of transfer functions were proposed in order to identify the relationship between the kinetc energy of the impulsive excitation forces (such as the piston slap forces and the valve seating impact forces) and the induced engine structure responses. These new transfer functions could be determined under motoring conditions and can greatly overcome the difficulties in estimating the engine structure responses.
Power series for the reverberation time
Authors: Joyce W. B.
Published: October 2005

The reciprocal of the reverberation time T is expressed as a power series in the absorptivity of the enclosure. The leading term of the series is found to be the Sabine–Franklin expression, and the procedure is thus interpreted, for weakly absorbing enclosures, as a new derivation and confirmation of that still controversial expression. The next term of the series then provides a correction to the Sabine–Franklin value in many practical cases of intermediate absorptivity where the Sabine–Franklin value is reasonably accurate but not accurate enough. Four other formulas which have been advanced as improvements on Sabine–Franklin are shown to yield unreliable corrections which are even of the wrong sign in some enclosures. Finally, it is shown that T bears a simple relation to the gain g of a laser, and, thus, existing evaluations of either gor T are immediately interpreted as evaluations of the other.
Scattering of stationary acoustic waves by an elastic obstacle immersed in a fluid
Authors: Boström Anders
Published: October 2005

The scattering of stationary acoustic waves by a bounded elastic obstacle in an inviscid fluid is considered. The developed formalism is an extension of the transition matrix method, which has been given by Waterman for acoustic, electromagnetic, and elastic scattering. In fact the problem at hand is more complex than the elastic case, something which is apparent in the solution. It is possible to obtain some different forms for the transition matrix, depending upon whether the Rayleigh hypothesis enters or not. It is worthy of notice that the more general formalism, i.e., the one not assuming the Rayleigh hypothesis, is also the more efficient numerically. Numerical results are given for spheroids and an object resembling the number ’’8.’’
The interaction of whole body vibration and impulse noise
Authors: Hamernik Roger P. , Henderson Donald , Coling Donald , Slepecky Norma
Published: October 2005

Three groups of chinchillas, each consisting of five monaural animals, were exposed to one of three conditions: 1 h of sinusoidal, 30-Hz vibration at 1 g rms; 50 noise impulses at 155 dB, 1.5-m A duration, at the rate of 1/min; or a combination of the vibration and the impulse noise. Before exposure, and at various times after exposure, each animal’s auditory evoked responses (AER) were measured at seven frequencies between 0l5 and 8.0 kHz. Thirty days after the exposure all animals were sacrificed for cochlear surface preparation histology. Chinchillas exposed to the vibration alone showed no significant temporary or permanent change in AER thresholds. The group exposed to impulse noise showed a maximum median TTS of from 34 dB at 0.5 kHz to 72 dB at 2 kHz and a flat PTS of 15–20 dB between 1 and 2.8 kHz. The combination group at all test times and frequencies showed a greater TTS and PTS than did the groups exposed to noise or vibration alone. The cochleograms are related in a variety of ways with hearing thresholds. The data from all three groups of experimental animals are consistent and demonstrate a potentiating effect of vibration on an impulse noise exposure.
Surface wave interpretation of the eigenfrequencies of a finite-length fluid cylinder
Authors: Gaunaurd G. C. , Tanglis E. , Überall H.
Published: October 2005

The eigenfrequencies of a finite-length fluid cylinder may be interpreted as the resonances caused by the phase-matching of circumferential waves that circumnavigate the cylinder along certain helical paths, and that get reflected back and forth from its top and bottom flat surfaces. In this paper we obtain the dispersion curves of these circumferential waves that correspond to a series of well-defined pitch angles of their helix for different values of the cylinder’s length-to-radius ratio.
Forced oscillations of a separated shear layer with application to cavity flow-tone effects
Authors: Elder Samuel A.
Published: October 2005

Wave boundary conditions near the point of separation at a sharp edge are carefully examined, with new insights being derived for some common flow-tone situations. Application of the continuity of velocity principle enables the amplitude and phase of the instability wave to be related to the acoustic driving wave phasor. Likewise, continuity of shear stress leads to a mathematical dependence of shear layer dynamics on upstream wall boundary layer parameters. Some surprising results: (1) An instability wave driven near the point of separation is found to move initially at half the velocity expected from linear theory. (2) Although resonator-controlled flow tones operate at levels above the nonlinear saturation point for shear layer instability, they can exist only for shear layers that would otherwise be highly unstable. Some longstanding mysteries cleared up: (1) Why unflanged resonators (e.g., coke bottles) resist excitation by flow at grazing incidence. (2) Why flow-tone spectra are nearly pure sine waves, even for multimode cavity systems.
Robust sequential detection of weak signals in undefined noise using acoustical arrays
Authors: Dwyer Roger F.
Published: October 2005

In detection problems where the noise distribution may be unknown, employing nonlinear elements that precede the standard detector often significantly improves system performance in non-Gaussian noise. However, in order to optimize the system to the noise conditions and, thereby, prevent degradation under Gaussian noise, the nonlinear elements should possess an inherent capability for adapting to the changing noise conditions. This paper presents a discrete formulation based on m-interval partitioning for sequentially detecting weak signals in undefined noise. Partitioning requires knowledge of a small number of quantiles and related functions from the unknown noise distribution. The resultant detector is easily implemented and is adaptable to slowly changing noise conditions. Two examples are given that clearly show improved performance, over a wide class of noise distributions, for an array employing m-interval partitioning compared with arrays employing linear correlators and sign detectors.
A model of lateral line microphonic response to high-level stimuli
Authors: Boston J. R.
Published: October 2005

The electrical potential recorded from the lateral line canal organs of fish in response to a sinusoidal vibratory stimulus consists of a microphonic component with frequency twice that of the stimulus plus a dc shift. This paper describes the behavior of both components as functions of stimulus frequency (from 100 to 400 Hz) and amplitude. The microphonic decreases with frequency, while the dc shift increases, and the two components have different input-output functions. An analytical model of hair cell electrical properties with an asymmetric saturating nonlinear conductance is presented that describes the behavior of both the microphonic and the dc shift.
Reflections on reflections
Authors: de Boer E. , MacKay R.
Published: October 2005

Most cochlea models consider the system as a pair of channels separated by a flexible membrane (basilar membrane). In the part of the wave where the stiffness of the membrane dominates, traveling waves are set up. Because of varying propagation conditions the speed of propagation diminishes most rapidly when the wave approaches the region where the basilar membrane shows resonance for the frequency under consideration. It might be expected that such a rapid change of propagation velocity gives rise to reflection. In this paper a one-dimensional model is considered in such a way that resonance properties stand out clearly. The results show that even when extremely little damping occurs (damping factor less than 10−3) virtually no reflection is evident. Under conditions of low damping the nature of the response is such that it is incompatible with inner hair cell or nerve fiber responses from the cochlea: some kind of ’’sharpening mechanism’’ should be present. Limitations of the model considered should be studied further to verify the conclusions in more general cases. Despite these limitations the present model serves to illustrate typical physical phenomena, like reflection and energy dissipation, quite well.
Level effects in psychophysical two-tone suppression
Authors: Duifhuis H.
Published: October 2005

Measurements of psychophysical two-tone suppression in a number of subjects are described. Levels of the stimulus components (suppressee, L1, and suppressor, L2) were the primary experimental variables. In all experiments the pulsation threshold was used with the probe frequency fP fixed at the suppressee frequency f1. In an initial experiment f1 was fixed at 1 kHz. The suppressor frequency f2 ranged from 0.2 to 1.4 kHz. At appropriate levels all subjects showed significant suppression. Suppression was found to decrease to zero as f2 approached f1. The amount of suppression depended on both L1 and L2 in a way not accounted for by any of the current theories of two-tone suppression. At higher overall levels suppression became increasingly prominent. The amount of two-tone suppression in a given stimulus condition depended strongly on the subject. The maximum amount of suppression measured was about 35 dB. In a second experiment it was verified that suppression follows the same pattern at other frequencies f1 (0.5, 2, and 4 kHz). Data for equal f2/f1 ratios were quite similar. The two-tone suppression effect decreased in a noisy environment. Within a 20-dB range of signal-to-noise ratios the effect of noise changed from negligible to the virtually complete elimination of two-tone suppression.
Comment on ’’On the mechanism of transduction in optical fiber hydrophones’’ [J. Acoust. Soc. Am. 66, 976–979 (1979)]
Authors: Moffett Mark B. , Shajenko Peter , Frye John W.
Published: October 2005

Price’s argument for the existence of zero longitudinal stress along the fiber in a fiber-optic hydrophone is shown to be fallacious.
Comments on ’’On the mechanism of transduction in optical fiber hydrophones’’ [J. Acoust. Soc. Am. 66, 976–979 (1979)]
Authors: Thurston R. N.
Published: October 2005

In a recent paper [H. L. Price, ’’On the mechanism of transduction in optical fiber hydrophones,’’ J. Acoust. Soc. Am. 66, 976–979 (1979)] it is concluded from static arguments that an optical fiber subjected to hydrostatic pressure undergoes an increase in length because the fiber is ’’squeezed out’’ toward the ends by the transverse pressure on its sides. We show that this conclusion is not correct. Static equilibrium demands that the stress in the fiber be hydrostatic just as in the surrounding fluid and that an increase in pressure be accompanied by a decrease in fiber length. We further point out that reference to appropriate original optical data taken under hydrostatic pressure renders the calculation of physical length changes unnecessary in the calculation of optical hydrophone sensitivity.
The development of high-efficiency narrow-band transducers and arrays
Authors: Widener M. Ward
Published: October 2005

A design method for high-efficiency transducer elements and arrays is described. Vibrational nodal suspension is used with a quarter wave mass load coupled directly to the medium. A quarter wave ceramic driver is connected to the mass by adhesive and isolated from the medium by an air cavity. Arrays have been constructed with efficiencies in excess of 90%. Elements and arrays are simple to construct and are relatively low in cost. The design technique has been successfully employed in the range of frequencies from 30 to 300 kHz.
Categorical features in speech perception and production
Authors: Goldstein Louis
Published: October 2005

Multidimensional scaling analyses of three types of English consonant confusions are reported: consonant substitutions in spontaneous speech errors, CV perceptual confusions, and VC perceptual confusions. Two data sets of each type are analyzed to assess reliability. Three reliable dimensions emerge in all data sets, corresponding to voicing, stop/fricative, and place of articulation. Representation of consonants in terms of categorical phonological features exhaustively describes what is common to the configurations of different data types, even though there is reliable detail within each data type that is not captured by categorical features. Such features can be viewed as groupings of speech sounds common to various perception and production processes.
Gaussian–Laguerre description of ultrasonic fields—Numerical example: Circular piston
Authors: Cavanagh E. , Cook B. D.
Published: October 2005

The sound field produced by plane baffled transducers of high ka can be described by treating the radiated space as a waveguide of infinite size. Under the Fresnel approximation for cylindrical geometries, the modes of this waveguide are known to be the Gaussian–Laguerre functions. The general Gaussian–Laguerre formulation for expanding acoustic fields is presented and numerical results are shown for the circular piston. The Gaussian–Laguerre expansion coefficients for this example are obtained analytically, thus providing a new solution in series form.
Amplitude distribution of pulses produced by shock waves due to cavitation bubbles
Authors: Gimenez G. , Kortnev A. A.
Published: October 2005

The authors study the amplitudes of the pulses delivered by a piezoelectric sensor immersed in a cavitation field. A 1024-channel analyzer shows that the amplitude distribution of these pulses includes peaks. They go on to show the pattern of evolution of this distribution as a function of the ultrasonic power and the distance between the piezoelectric sensor and the transducer.
Influence of data window shape on detectability of small cw signals in white noise
Authors: Robertson G. H.
Published: October 2005

The power spectrum of a white noise waveform modified by an arbitrary, real data window is derived. It is shown that the weight of a component at frequency f relative to the cumulative weights of all other components in estimates of the power density at this frequency is greatest when a rectangular data window is used. On this basis it is concluded that the detectability of a small cw signal in white noise is greatest if a rectangular data window is used. Some examples are worked out to show the estimated loss in detectability when various other windows are used.
Segmenting speech into words
Authors: Cole Ronald A. , Jakimik Jola , Cooper William E.
Published: October 2005

Four experiments employed a listening for mispronunciations task to determine how listeners perceive an ordered series of words from a continuous, phonetically ambiguous stimulus. In experiments 1, 2, and 3, listeners’ reaction times to detect mispronunciations were obtained in phonological sequences that could be perceived as either one or two words (e.g., ’’cargo’’ or ’’car go’’ mispronounced ’’carko’’). In experiment 1, segmentation of the acoustic signal as one or two words was guided by the theme of a short story. For example, the sentence ’’They saw the carko on the ferry’’ was spliced into two stories—one about a shipment of cargo, and one about a car about to go on a ferryboat. The results showed significantly faster reaction times—by about 300 ms—when the mispronunciation was perceived as occurring in the second syllable of a word. In experiment 2, alternate segmentations of the same acoustic signal were constrained by the grammatical nature of the first few words in a sentence. Subjects were presented with sentences such as ’’The doctor said that nosetrops will help the cold’’ or ’’The doctor said he knows trops will help the cold.’’ By means of tape splicing, the final portions of the two sentences in each pair were acoustically identical. Reaction times were again found to be faster—by about 150 ms—when the mispronunciation was perceived as occuring in the second or third syllable of a word, rather than at the beginning of a word. Experiment 3 replicated these results using naturally recorded sentences having normal prosody. The results of experiments 1–3 demonstrated that prior context determines how syllables are recognized as words and that a mispronounced second syllable is detected faster than a mispronounced word-initial syllable. It was argued that mispronunciations are detected more quickly in second syllables because the intended word has been accessed from its first syllable. This hypothesis was further supported in experiment 4. When subjects read each sentence before hearing it, so that all syllables were equally (and perfectly) predictable, mispronunciations were detected equally fast in first and second syllables.
Connection of acoustic beam displacement, cycle distances, and attenuations for rays and normal modes
Authors: Tindle C. T. , Weston D. E.
Published: October 2005

Several theoretical results linking ray and normal-mode quantities are derived by assuming Wentzel–Kramers–Brillouin (WKB) solutions for the depth dependence of the acoustic field in both water and bottom. Some of the results are not new but are extended here to the general case of reflection from a structured, lossy bottom: (1) Mode and ray cycle distances are equal if the ray cycle distance includes the beam displacement on reflection; (2) cycle distance is simply related to the normalization of the normal modes; (3) mode attenuation per cycle is equal to bottom loss per bounce of the equivalent ray; (4) a complete normal-mode solution for water may be obtained from the plane-wave reflection coefficient with no further knowledge of the bottom; and (5) the WKB solution for the bottom is equivalent to a calculation assuming interfering geometric ray paths.
Acoustic scattering from a submerged plate. I. One reinforcing rib
Authors: Woolley Barry Lee
Published: October 2005

Theoretical calculations of the backscattering of a plane sound wave by a rib stiffened Timoshenko–Mindlin plate are presented. An exact solution is compared with two saddle point integral approximations. One saddle point integral approximation takes into account the near coalescence of the leaky wave pole and the saddle point. Mass loading of the rib and different rib constraints are discussed. The range of validity of the model is also given.
Acoustic scattering from a submerged plate. II. Finite number of reinforcing ribs
Authors: Woolley Barry Lee
Published: October 2005

Theoretical calculations of the backscattering of a plane sound wave by a rib stiffened Timoshenko–Mindlin plate are presented. Equations are derived for the calculation of the influence of N arbitrarily situated, arbitrarily loaded ribs on the amplitude of the reflected wave. Calculated results for two, nine, ten, and an infinite number of equally spaced ribs are given.
A simplified approach to optimum quadrature sampling
Authors: Brown J. L.
Published: October 2005

A deterministic bandpass signal x(t) bandlimited to ‖ ω ‖ ε I1≡(ω0−σ/2, ω0+σ/2) can be represented in the form x(t)=p1(t) cosω0′t−q1(t) sinω0′t, where p1, q1 are low-pass (the ’’in phase’’ and ’’quadrature’’) components bandlimited to ‖ ω ‖?σ/2+‖ ω0−ω0′ ‖ and ω0′ is an arbitrary frequency within the band I1. Quadrature sampling has as its aim the recovery of the low-pass components p1, q1 directly from samples of both the bandpass signal x(t) and its quarter-wavelength translation x(t−π/2ω0′), the samples being taken at a low-pass rate. Grace and Pitt [J. Acoust. Soc. Am. 44, 1453 (1968)] obtained a result for the case ω0′=ω0?σ requiring an overall or average sampling rate of (σ/π)(γ/[γ]) samples/s, where γ=ω0/σ and [⋅] denotes the greatest integer function. By reducing the problem to an application of the classical Shannon sampling theorem in a special case (2ω0/σ =integer) and then proceeding to the general case via an embedding technique, we arrive here at an improved average sampling rate of (2γ+1/[2γ+1])(σ/π) samples/s. The method, assuming only ω0?σ/2 and finite energy signals, provides a simpler and more accessible treatment of the quadrature sampling problem than the earlier techniques of Grace and Pitt, Kohlenberg [J. Appl. Phys. 24, 1432 (1953)], and the author [IEEE Trans. Aerosp. Electron. Syst. AES-15, 366 (1979)].
Five decades of research on cochlear mechanics
Authors: Zwislocki J. J.
Published: October 2005

A review of Békésy’s experiments on postmortem preparations shows the fundamental features of cochlear macromechanics. Early mathematical theory was able to explain Békésy’s observations in terms of the hydrodynamics of surface waves and to account for some experimental artifacts. More recent experiments in vivo have shown that the cochlear frequency analysis is sharper than observed by Békésy and may occur in two interacting stages. It is suggested that the second stage may result in part from a resonance of hair-cell stereocilia loaded by the mass of the tectorial membrane, and it is calculated that the damping is small enough to allow such a resonance. The resonance would make the basilar membrane with the organ of Corti appear as a fourth- rather than a second-order system.
Cochlear partition vibration—Recent views
Authors: Rhode William S.
Published: October 2005

Recent measurements obtained with a variety of techniques have extended von Békésy’s observations of cochlear-partition mechanics including the traveling-wave pattern and the frequency-place relation. Whereas the cochlear filter has been shown to be sharper than expected, on the basis of Békésy’s results, it apparently is not sharp enough to account for the frequency selectivity observed in auditory nerve fibers. The main remaining question is whether the vibration of the basilar membrane is linear or not. Steady-state nonlinearities that disappear rapidly upon death, transient nonlinear response, and two-tone suppression have been observed in the mid-frequency range in one animal species. Whether the linearity–nonlinearity controversy arises from a species difference or a frequency-place difference remains to be resolved.
Effects of ultrasound on catalase and malate dehydrogenase
Authors: Kashkooli H. Ali , Rooney James A. , Roxby Robert
Published: October 2005

Catalase and malate dehydrogenase (MDH) were subjected to the sound field produced by a transversely oscillating wire driven at 20 kHz. Catalase was not inactivated under any conditions of sonication whereas MDH inactivation increased exponentially with the duration of sonication and depended upon the initial enzyme concentration. The inactivation was not the result of collapse cavitation or thermal inactivation and was probably related to the presence of acoustic microstreaming.
Reciprocity principle in duct acoustics
Authors: Cho Young-chung
Published: October 2005

Various reciprocity relations in duct acoustics have been derived on the basis of the spatial reciprocity principle implied in Green’s functions for linear waves. The derivation includes the reciprocity relations between mode conversion coefficients for reflection and transmission in nonuniform ducts, and the relation between the radiation of a mode from an arbitrarily terminated duct and the absorption of an externally incident plane wave by the duct. Such relations are well defined as long as the systems remain linear, regardless of acoustic properties of duct nonuniformities which cause the mode conversions.
Axisymmetric free vibration of a submerged spherical shell
Authors: Felippa Carlos A. , Geers Thomas L.
Published: October 2005

Previous studies of the title problem have produced only partial solutions for this classical configuration. The present study shows how complete solutions are readily obtained from simple polynomial expressions. Numerical results in graphical form are presented for a steel shell submerged in water as functions of a parameter related to the shell’s thickness-to-radius ratio. It is found that descriptions based upon added-mass and added-damping perturbations of the shell’s in vacuo free-vibration characteristics can be misleading.
Viscous attenuation of sound in suspensions and high-porosity marine sediments
Authors: Hovem Jens M.
Published: October 2005

The Biot theory for sound propagation in porous media has been specialized to suspensions of particles and compared with an earlier model based on scattering theory, for sound velocity and viscous attenuation in suspensions. It is shown that the Biot theory gives fairly correct predictions of attenuation as a function of concentration, whereas the suspension model fails when the concentration exceeds a few percent. The reason for this is discussed and a modification to the suspension theory is proposed. This theory has been applied to study viscous attenuation as a function of frequency and it is shown that viscous attenuation may have an almost linear dependence on frequency when account is taken of distributed grain sizes.
Autonomic system activity and performance on a psychomotor task in noise
Authors: Kryter Karl D. , Poza Fausto
Published: October 2005

Subjects were exposed to alternate conditions of quiet and noise (computer line printer noise at 100 dB, A-weighted) while performing a demanding, rapidly paced, psychomotor task. Heart rate, peripheral pulse amplitude, and peripheral blood volume were monitored throughout four 8-min test sessions. There appeared to be no increase in physiological stress or in errors in task performance during the noise as compared to the quiet test segments. An attempt is made to explain possible causes of differences between the results obtained in this study and those reported for a earlier, somewhat similar, study by Cohen et al. [’’Noise Effects, Arousal, and Human Information Processing Task Difficulty and Performance,’’ Department of Psychology and Industrial Engineering, North Carolina State University, Raleigh, NC (1973)].
An ultrasonic pulse-echo system that makes use of interaural localization
Authors: Ueda Mitsuhiro , Uda Koji
Published: October 2005

A new type of ultrasonic pulse-echo method that makes use of interaural localization is described in this Letter. The basic idea of this method is to receive pulse echoes reflected from an object with two receiving transducers and to hear the echo signals stereophonically after they are converted to audible frequencies. The principles of the system and some results of preliminary experiments that make use of an ultrasonic pulse of 500 kHz are presented.
Fan noise reduction by single- and double-wall barriers
Authors: Lohmann Dieter
Published: October 2005

In the case where the source of sound is a turbo-jet engine fan the solution of Fresnel–Kirchhoff’s diffraction integral contains an additional term. That term may be neglected when the source of sound is a single harmonic point source. Formulas, including this term, show that behind a barrier the fan noise is amplified instead of being reduced. The amplification effect occurs when the rim of the barrier is located in areas of high or rather maximum sound levels. It was found out that double-wall barriers prevent sound amplification. This additional abatement of sound in the shadow zone of the screen is partially caused by absorption of diffracted waves within the open double-wall ’’cavity.’’ A semi-empirical formula was developed to estimate this absorption. As basic configuration for experimental studies a DC-10 half model with a CF6-turbo fan engine was selected to be tested in model scale of 1 :10. All test runs were conducted in an anechoic chamber of the DFVLR, Department of Technical Acoustics, Germany. The agreement between theory and experiment is satisfactory.
The scattering of sound by turbulence in water
Authors: Korman M. S. , Beyer R. T.
Published: October 2005

This paper describes experimental results on the scattering of sound by turbulence in water. The turbulence is created by a 1-in.-diam submerged water jet, nozzle velocity 648 cm/s. The sound frequency is 1 MHz. The spectral broadening of the monochromatic signal (due to the scattering of the sound by the turbulent eddies) is compared for different forward scattering angles in the case of incident plane and cylindrical waves. A theoretical model is presented to explain the plane-wave results. Results for the scattering of cylindrical waves are compared with experiments performed by Candel and Julienne [AIAA Paper No. 76-545, 3rd AIAA Aero-Acoustics Conference, Palo Alto, California (July 20–23, 1976)] in air with spherical wave sources.
Stability and identification of ocean acoustic multipaths
Authors: Spiesberger John L. , Spindel Robert C. , Metzger Kurt
Published: October 2005

A phase-coded signal with 64-ms resolution was transmitted at 10-min intervals for a 48-day period between an acoustic source moored at 2000-m depth and a bottom mounted receiver at ∠3000-m depth and at ∠900-km range. About 16 multipaths were resolved. They were stable in the presence of ocean fluctuations and could be identified (with some exceptions) from ray theory. The precision to which daily travel-time fluctuations along multipaths could be measured was better than 10 ms. The resolution, stability, identification, and precision is adequate for acoustic monitoring of mesoscale ocean variability by measuring travel-time variations along ray paths.
Uniform asymptotic evaluation of the continuous spectrum contribution for the Pekeris model
Authors: Stickler D. C. , Ammicht E.
Published: October 2005

The determination of the continuous spectral contribution to the transmission loss in ocean acoustics can be very difficult. While it is applicable to very general sound-speed profiles, a uniform asymptotic method, i.e., one that is valid as the proper modes pass through cutoff, is proposed and illustrated for the Pekeris model. The method exploits the fact that there are singularities near the integrand of an integral representation of continuous spectrum and that these singularities determine the asymptotic behavior of the continuous spectrum. Numerical examples illustrate the influence of the proper, real improper, and complex improper modes on the continuous spectrum. The technique avoids the sometimes costly numerical evaluation of the continuous spectral contribution; however, the improper eigenvalues must be found.
Acoustics of gas-bearing sediments. II. Measurements and models
Authors: Anderson Aubrey L. , Hampton Loyd D.
Published: October 2005

Acoustical properties of water saturated and gassy sediments are observed to be significantly different. The present state of knowledge of the acoustical properties of saturated sediments, gassy water, and gassy sediments is reviewed in a companion paper. The dynamics of bubbles in water and in various solid materials, including sediments, are experimentally examined here. Pulsation resonance is exhibited by the bubbles in all materials examined. Predictions of bubble resonance frequency and damping are shown to agree with the measurements. Equations for sound speed and attenuation, based on the model of resonating gas bubbles, are shown to agree with published measurements in gassy sediments. Parameters required for predicting gassy sediment acoustical properties are identified. Ranges of values of these parameters for various sediments are discussed.
Scattering by a smooth elastic obstacle
Authors: Boström Anders
Published: October 2005

In the present paper we adapt the transition matrix method to the case of a smooth elastic obstacle. The boundary conditions employed are discussed in some detail and are seen to be responsible for the fact that the rather complicated formal solution in many respects resembles that for an elastic obstacle in a fluid. Comparisons are made between the smooth and the usually employed welded obstacles, and for spheres approximate expressions are given for the transition matrices in the long wavelength limit. Numerical results (cross sections and surface stresses) are given for spheres and spheroids, and it is then seen that often the smooth and welded obstacles, at least qualitatively, show similar features.
Reflection and transmission of plane elastic waves at the boundary between piezoelectric materials and water
Authors: Noorbehesht Behzad , Wade Glen
Published: October 2005

Reflection and transmission coefficients for plane elastic waves obliquely incident on the boundary between two isotropic materials have been known for some time. The solution for anisotropic materials, however, has not been fully treated in the literature. Here we derive these coefficients for the case of a piezoelectric ceramic in contact with water. This problem is of significant practical interest, since in a variety of applications, piezoelectric ceramics, which are inherently anisotropic, are used as transducers to radiate acoustic energy into water. Due to the anisotropy, velocities of both compressional and shear waves are functions of the angle of incidence. Piezoelectric equations are solved to find the variations of compressional and shear wave velocities with the angle of incidence. Reflection and transmission coefficients are then obtained and numerical results are presented for four piezoelectric ceramics.
Frequency approach to nonlinear dispersive waves
Authors: Korpel A.
Published: October 2005

Coupled equations are derived which describe the evolution of harmonic content for quadratic nonlinearity in the presence of arbitrary attenuation and dispersion. The equations are shown to be in agreement with known results of nonlinear acoustics and to describe novel phase locking and parametric phenomena when applied to dispersive systems. They are well suited to a planned computer analysis concerning the existence of solitary waves in systems with topological dispersion.