bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrimination-level differences (DLD's) as a measure of the uniqueness of speech
Authors: Tobias Jerry V. , Kidd Gerald D.
Published: October 2005

The analysis of speech signals is often reported to be different from the analysis of nonspeech signals. From the premise that this difference is characteristic not of the speech/nonspeech nature of a sound, but of a meaningful/meaningless dichotomy, binaural masking tests were made on a hierarchy of six computer-generated approximations to speech, all with similar temporal patterns; they ranged from a nonsense syllable through a shaped noise and a tone burst. Two kinds of tests were run, one at and one above threshold. The at-threshold test was a simple masking-level-difference measurement that compared homophasic (N0S0) with antiphasic (N0Sπ) detection of each signal. The above-threshold test was comparable to an intelligibility-level-difference measurement (also comparing N0S0 with N0Sπ presentations); however, subjects were asked to discriminate the six types of sound rather than to recognize words. The result is a discrimination-level difference (DLD). In preparation for this identification experiment, listeners learned to discriminate the signals in the quiet and at favorable signal-to-noise ratios; practice continued long past the time when they could make 100% correct judgments. Apparently as a result of this overtraining, subjects gave DLD's for the speech signals that differ little if at all from the DLD's for the nonspeech signals—even for those at the other extreme of the hierarchy. This finding suggests that once a sound is identified as having a special communicative function, it is specially treated by the auditory system, much as many of us have always assumed that speech is specially treated. Additional data will be presented comparing detection performance with identification performance.
Sub-bottom profiling with hydroshock impulse source
Authors: Bouyoucos J. V. , McLaughlin J. K. , Nelson D. E.
Published: October 2005

Hydroshock is a form of impulse source in which a controlled, imploding flow is converted to an acoustic impulse without after shot clutter. Hydroshock III was used recently in an experiment with a short hydrophone line array to examine the sub-bottom returns from Seneca Lake. The source and receive array were towed near the surface over regions where the depth of the lake was approximately 500 ft. Sub-bottom structure to sub-bottom penetrations in excess of 600 ft was delineated. The experiment will be described, and the contributions of the source waveform to the resolution of sub-bottom structure will be discussed. This research has been supported by the Office of Naval Research, Code 222.
Crystal-controlled pump signal source for an experimental parametric acoustic receiving array
Authors: Olsen W. S. , Goldsberry T. G. , Reeves C. R. , Rohde D. F.
Published: October 2005

In the Parametric Acoustic Receiving Array (PARRAY), a locally generated, high-frequency carrier (or pump) wave is modulated in the water by a low-frequency acoustic wave. The information in the low-frequency signal appears as low-level modulation side bands of the pump wave; therefore, the side-band noise of the pump-signal source is an important PARRAY system parameter. Since commercial oscillators with adequate spectral purity were not available, a program was initiated to develop a 65-kHz crystal-controlled oscillator with sufficient spectral purity for use as the pump-signal source in an experimental PARRAY. Application of state-of-the-art techniques and components has enabled the design and construction of a crystal-controlled oscillator with spectral purity previously unattainable in this frequency region. Spectral purity of this oscillator is approximately four orders of magnitude better than commercially available oscillators in the 65-kHz frequency region. Measurements performed on the oscillator show that the spectrum level side-band noise referenced to the carrier level is better than −170 dB for frequencies greater than 100 Hz away from the carrier. The oscillator design is described in detail and side-band noise test data are presented and discussed. [This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Naval Electronics Systems Command under Contract NO0039-76-C-0231.]
Analysis for fill-time effects on cylindrical arrays
Authors: Stokes R. H.
Published: October 2005

When a plane wave impinges on a cylindrical array, the leading edge insonifies the first few elements of the array. As the wave front continues past the leading edge of the cylinder, more and more elements are insonified until all elements in the array are insonified. This time between the first and last element to be insonified is called array “fill time.” For a phase-shift beamformer, where the insonifying pulse length is long compared to the fill time, the resultant beam pattern is essentially the same as from a planar array of similar aperture or a cylindrical array with a delay line beamformer. When the pulse length and the fill time are approximately the same, there has been no detailed description of how the beam pattern is affected. Accordingly a thorough analysis of array fill time has been made of a cylindrical array, phase-shift beamformer in comparison to a delay line beamformer and to a planar array. The conclusion reached from this study is that there is little effect on the array beam pattern due to the fill time as long as the fill time is no greater than the pulse length. [Work supported by NCSL.]
Underwater acoustic television transmission via the parametric source
Authors: Konrad W. L.
Published: October 2005

The narrow-beam wide bandwidth characteristics of the parametric difference radiator are particularly advantageous when applied to wide-band, multipath sensitive transmissions such as graphics or television. The results of a television-transmission test conducted over a range of 4 km at the NUSC Seneca Lake facility are described. [Work supported by NUSC.]
Concert hall measurements during musical performances
Authors: Schroeder M. R. , Möller W. J.
Published: October 2005

Most acoustical measurements of concert halls are made in unoccupied halls. This paper describes how to use the music signal, recorded by microphones on the stage during a musical performance, as a test signal to measure reverberation time, early and late energies (“clarity”), modulation transfer functions, pronounced echoes and other perceptually important aspects of the hall's impulse response.
Perceptual factors of small room reverberation
Authors: McDermott Barbara , Allen Jont
Published: October 2005

Room reverberation has a well recognized characteristic quality which can be annoying in a conference telephony environment. The subjective factors of reverberent speech were studied by asking listeners to judge speech samples in which the short-term and long-term reverberation times the independent variables. Synthetic room impulse responses were generated on a digital computer based on an image model of a room. Four microphone-loudspeaker distances were combined with four wall adsorption coefficients, giving a total of 16 distinct room conditions. Speech samples consisting of ten sentences spoken by each of four talkers were reverberated by the 16 room conditions. All possible pairs of the 16 room conditions were presented to listeners for judgment. The subjects were asked to use a scale from zero to nine to report how different they thought the speech sounded in each pair of rooms. These data were analyzed by a scaling procedure that relates the difference judgments to a distance in a multidimensional perceptual space (INDSCAL). Our success in relating physically measured variables derived from the impulse responses to the factors of the perceptual space will be discussed.
Correlation between physical values and fullness of bass sound reproduced by a loudspeaker in a listening room
Authors: Sakai S. , Suzuki F. , Yamamoto T.
Published: October 2005

Variation of the fullness of bass sound according to the setting positions of a loudspeaker was studied in a dead- and a typical listening room. Subjective experiments were carried out on test sounds of a symphony, a piano sonata, and base strings by applying the paired comparison and the successive categories methods. Subjective values were expressed on a scale of five or seven points. The results were analyzed by means of the multidimensional and the Thurstion's Case V scaling methods. About 200 physical values calculated from steady-state frequency responses and transient characteristics were also selected. At first, physical values with high correlation to the subjective values were extracted by the varimax method, and the correlations between these values were analyzed. According to the results, the sensation of bass sound is correlated with the steady-state frequency response rather than the transient characteristic, and it has the highest correlation with the energy of the frequency range from 125 to 315 Hz. The correlation coefficient is more than 0.95.
Estimates of oceanic backscattering correlation time at 87.5 kHz
Authors: Pinkel Robert , Greenblatt Paul
Published: October 2005

Doppler sonar is becoming a powerful tool for the remote measurement of the upper ocean water velocity field. Theoretically, precision in the Doppler velocity estimate is limited by the signal to noise ratio of the return, and the ambiguity properties of the transmitted pulse. At fixed signal to noise, the actual precision can be degraded considerably if differences in relative motion of the scatterers in the scattering volume “decorrelate” the return, resulting in Doppler broadening. The return will be significantly decorrelated if scatterers change their relative positions on the order of a wavelength while the transmission is passing through the scattering volume. The limits to peak transmitted power, and typical backscatter strength and ambient noise level in the sea are well known. However, little information exists on the scattering correlation time for typical oceanic conditions. An experiment was conducted from FLIP during June 1977, using a narrow beam 87.5-kHz sonar. Pulses of duration 29–90 ms were transmitted horizontally, at 85-m depth. From the calculated autocorrelation functions, the importance of the relative motion of the scatterers can be determined.
Acoustic detection of neutrinos
Authors: Westervelt Peter J.
Published: October 2005

When high energy neutrinos interact with nucleons in the ocean a jet of hadrons is produced which deposits thermal energy. This thermal energy is expected to produce a sonic pulse which hopefully will be sufficiently intense and directional to enable the energy and direction of incidence of the primary neutrino to be determined [Antares Parvulescu, J. Acoust. Soc. Am. 61, 580(A) (1977)]. This paper discusses the physical mechanism whereby the energy of the neutrino is converted into a sound pulse. A simple model will be exploited to account for the signature expected from such an event. [Work supported in part by the U. S. Naval Ocean Research and Development Activity and by the U. S. Department of Energy.]
Acoustic signals from heavy nuclei in various liquids
Authors: Jones W. V. , Bowen T. , Bowler M. , Bradner H. , Camerini U. , Ellison B. , Hunter S. , Jones W. V. , Learned J. , Malbrough D. , March R. , Murphy D. , Parvulescu A. , Pifer A. , Snider R. , Wust C. , Zabouni N.
Published: October 2005

Measurements of acoustic pulses produced by relativistic heavy nuclei in various liquids have been made at Lawrence Berkeley Laboratory. The observations utilized iron nuclei of 600 and 1900 MeV kinetic energy per nucleon, traversing liquid argon, carbon tetrachloride, and mercury. The acoustic signals due to ionization of the medium and its subsequent heating and expansion were received by a cylindrical piezoelectric transducer coaxial with the particle beam (selecting tracks within 1 mm of the axis). Signals were amplified, filtered, digitized (at the rate of 50 ns per sample) and recorded via computer on digital tape. Analysis is in progress at this time (July 1978). Results will be presented.
A screening device utilizing quantified reflex latency parameters
Authors: Richards G. R. , Mitchell O. C. , Bethea J. W.
Published: October 2005

The latency time of the intra aural muscle reflex was measured by constructing a comparator circuit coupled to a high speed digital clock which collected acoustic contralateral stimulus data from an acoustic impedance bridge circuit. Forty-six fourth-grade children were divided into two groups according to audiometric and otological findings; one group consisted of 20 normal hearing Ss, i.e., 10 dB (ANSI 1969) or better; the second group had 26 Ss who failed either/or the otological or audiometric examination. A point-biserial coefficient correlation found latency times below 520 ms significantly correlated with normal hearing at the 0.001 level and times above 520 ms correlated with impaired auditory systems at the 0.05 level of confidence.
Decay of the acoustic reflex under impact and steady-state noise exposure
Authors: Hétu R. , Côté B.
Published: October 2005

Acoustic reflex (AR) activity of seven normal hearing young adults was monitored continuously during a 15 mn monaural exposure to impact or steady-state noises of identical spectra. The impact noise was a recording of the flattening mill in a large foundry; the crest factor varied from 14 to 23 dB and the repetition rate was approximately 80 impacts per second. Both noise conditions were presented at a rms SPL of 106 dB. AR activity was measured through changes in acoustic conductance at the eardrum using a 660-Hz probe tone. The AR decreased to 30% of its original value after a 15-mn exposure to either noise condition. In terms of absolute values, the steady state noise induced significantly higher amounts of AR activity, as measured at the onset and at the offset of the noise. The AR decay values for the two conditions were significantly correlated (spearman rho) despite the absence of any corresponding relationship between magnitudes of on or off responses.
Criteria and procedures for evaluating industrial audiometric test data
Authors: Royster L. H. , Lilley D. T. , Thomas W. G.
Published: October 2005

Hearing threshold level data representing an industrial population of twenty industries and 30 000 employees has been collected. Different test retest criteria and changes in hearing threshold levels have been utilized in attempting to develop guidelines for evaluating industrial audiometric test data. A summary of the findings to date will be presented that includes a discussion of the observed long term learning curve that is a characteristic of all industrial audiometric data bases, if an effective hearing conservation program exists. In addition, data will be presented that demonstrates the need for initially separating the population into black and white, male and female subpopulations before an evaluation of the programs effectiveness is undertaken.
Digital control of dynamic-response histories
Authors: Stroud R. C. , Hamma G. A. , Smith S.
Published: October 2005

This paper describes the technology of dynamic-response-history (waveform) control, its development, and its current status. The presentation begins with review of the history of the waveform control, which has occurred since 1965. The advent of the Fast Fourier Transform (FFT) algorithm and the emergence of low-cost minicomputer were milestones in the development of digital-control technology. Their impact on waveform control are discussed. The fundamental theory of history control is presented; i.e., the concept of iterative corrections made in the frequency domain. The extension to multiexciter methods by replacing histories and spectra with vectors and matrices whose elements are histories or spectra is described. Problem areas are identified and potential solutions are summarized along with current research efforts. Commercially available systems are reviewed. Finally, a projection of likely future applications of of history-control technology ranging from near-term planned or potential applications to more-distant possibilities is presented.
An experimental research on the vibration transmission paths and their dynamic behavior of engine structure vibration
Authors: Okamura Hideo
Published: October 2005

The vibration transmission paths of gas force, the most dominant excitation force in diesel engine, were identified by exciting the piston top and cylinder head surface and measuring the acceleration response at piston, connecting rod, crankshaft, main bearing caps, and cylinderblock surface under static condition. A four-cylinder in-line high speed diesel engine was used for the test. The transfer functions for the paths were also measured in examining the fluence of crank angle, coolant, lubricant, and journal bearing pressure. The vibration behavior of the engine structure was examined by changing the assembling conditions stepwisely. In order to examine the dynamic behavior of the engine structure vibration, test was also carried on under motoring condition, and the structure responses due to gas force, piston slap, and valve seating impact and so on could be identified separately.
Temporal organization and prosody—perceptual aspects
Authors: Lehiste I.
Published: October 2005

The paper presents a review of recent research dealing with the perceptual aspects of temporal organization of spoken language and its prosodic structure. Special emphasis will be placed on the prosodic characteristics of discourse: units of spoken language that consist of more than one sentence. Results of a recent experiment will be reported, in which listeners were presented with filtered and unfiltered versions of a naturally produced narrative monologue, and were requested to identify sentence and paragraph and boundaries. The performance of the listeners in identifying boundaries will be correlated with the prosodic cues available to them in the filtered version, and the additional syntactic and semantic cues present in the unfiltered version. Analysis of listener responses makes it possible to separate the perceptual role of prosodic cues from that of syntactic and semantic cues. The distinction between the acoustic manifestation of sentence boundaries and paragraph boundaries will be likewise discussed.
Production and perception of segmental durations in spoken Japanese
Authors: Higuchi Norio , Fujisaki Hiroya , Sekimoto Sōtarō
Published: October 2005

As a step toward understanding the mechanisms by which segmental timing is determined, segmental durations are investigated both from the viewpoint of speech production and from that of speech perception using two-mora words consisting only of vowels. Assuming that the trajectories of formant frequencies can be approximated by step response functions of a critically damped second order system, the onset of articulatory control for the second vowel is estimated from the trajectories of formant frequencies, and is used as an index for the timing of the production of the second vowel. An analysis of the formant trajectories indicates considerable variability in the timing of production; the onset of the second vowel being earlier when articulatory differences between the first and second vowels are greater. On the other hand, the perceptual onset of the second vowel is determined by an identification test using truncated speech stimuli, and is used as an index for the timing of its perception. Results of the identification tests reveal comparatively small differences in perceptual timing, suggesting that the apparent diversity of timing at the level of speech production is induced to maintain the perceptual uniformity of segmental durations. [Work supported by Ministry of Education Grant-in-Aid for Scientific Research No. 31707.]
Maximum entropy source bearing estimation
Authors: Skinner D. P. , Hedlicka S. M. , Matthews A. D.
Published: October 2005

Results of a simulation study of the application of the complex one-dimensional maximum entropy spectral analysis algorithm to the problem of source bearing estimation using a linear array are reported. The rms error in the source bearing estimates was observed to increase with decreasing signal-to-noise ratio (SNR), when the model order (p) approached the number of array elements (N), and when the source of interest was not well resolved from adjacent sources. Typical rms errors observed (for p = N/2) were 0.1 λ/D at an SNR of 10 dB, 0.2 λ/D at 0 dB, and 0.5 λ/D at −6 dB. The statistical variability and number of spurious peaks in the array response were observed to increase rapidly as p approached N. At SNR less than 0 dB the array response, even when averaged over 50 independent data sets, indicated numerous spurious sources when the model order was large. The equivalent number of degrees of freedom (df) of the array response, estimated as twice the square of the average divided by the variance of the response, were calculated and compared with df = N/p as conjectured by Parzen. Parzen's conjecture was consistent with the observed results for p ≪ N, but was found to be very optimistic at high model orders.
Moving target indicator with two memories in which signals were stored in a pile
Authors: Ukigai M. , Miida Y.
Published: October 2005

In the acoustical engineering such as sonar technique, it is often necessary to take away periodic waves from reflecting signals. The designed moving target indicator can carry away periodic signals with simple curcuits. Only the signals of moving targets are taken out and especially would not disappear for a certain time after the stop of these movements. This time can be controlled by setting the value of a regulator of this circuits. This indicator has two memories in its circuits. The reflecting signals were stored repeatedly in these memories with particular ratios in a pile, respectively. The output of this indicator is taken out from the calculator in which the value of the function of a stored signal is successively divided by another one. Some experiments were performed in the air at the frequency of 40 kHz so as to verify the validity of the theory. In these experiments, the results qualitatively agree with the theory.
Coherence degradation in active sonar systems
Authors: Higgins R. C. , Francis J. T. , Kelly J. G.
Published: October 2005

This paper quantifies the degradation in performance of a quadrature receiver when the phase of the input target signal is time-varying and the background noise is additive Gaussian. The quadrature receiver, a conventional signal processor, consists of a replica-correlator followed by a quadratic detector. In active sonar systems with narrowband transmit signals, direct path and multipath returns from a distributed highlight target add at the receiver to produce a composite echo which has a time-varying phase over the signal duration. As a result, a mismatch in phase exists between the received signal and the replica (replica-correlator) causing a degradation in processor performance. This paper measures the amount of processor degradation using a general narrowband target signal model with random phase fluctuations which are characterized by a unimodal probability distribution and a known covariance function. The receiver degradation is presented functionally in terms of the output signal-to-noise ratio (SNR) and graphically in terms of the receiver operating characteristics (ROC) curves. When the phase is assumed to be piecewise constant from time interval-to-interval over the signal duration, it is shown that under certain conditions, the receiver output SNR diminishes by 3 dB for each doubling of the number of time intervals.
Detection of archaeological object by impulse sound
Authors: Matsuda M. , Ozawa K.
Published: October 2005

It is well known that the detecting system for an archaeological object, buried under the gound, is usually an excavation process. For the effective detecting, the scientific method such as magnetic or electric detection is occasionally used, but it cannot fill its function sufficiently. The authors have introduced the acoustical method. The fundamental detecting system is divided into three main parts: hammering source, sound detector, and signal processing to obtain the object image. The source generates an acoustic impulse of about 10 ms in duration. This impulse passes through the ground medium and is reflected by the object. The reflected impulse is observed by the BaTiO3 receiver set: 93 kHz of F0. Four receivers are fixed surrounding the source. The location of the object is computed by the data from the receivers through correlation and smoothing processes by using a digital computer. From the experimental results, it was found that this method is effective to determine the location of large scale object such as Key-Hole Tomb.
Velocity accuracy and performance characteristics of Janus acoustic Doppler navigator systems
Authors: Brigham G. , Nesto A.
Published: October 2005

The Janus radar Doppler navigator system has excellent velocity measuring accuracy which the analog underwater acoustic navigator system, using dual independent bottom and volume reverberation modes, cannot match. While considerable differences exist between aerospace and hydrospace vehicle dynamics, they can be largely mitigated using only millisecond delays in post time integration smoothing of the velocity-time history which results in small dynamic induced system errors. The transducer construction and installation errors are primarily random, small, and partially reducible in proportion to time and cost. The basic difference between the radar and acoustic system velocity accuracy is in the water reverberation mode which is necessary for the latter system in deep water. This error depends on ocean currents, upwelling, internal waves, etc., but most importantly on the water particle motion caused by the displacement of water as the hull moves. This paper is a review of the Janus acoustic system and the various intrinsic errors, including calculations of the limiting error due to water undergoing essentially incompressible flow around an ellipsoidal model of a submarine hull.
Program for integrated sonar modeling (PRISM)
Authors: Chaika E. D. , Granum R. M.
Published: October 2005

An interactive computer program has been written that evaluates sonar system performance. The PRISM system provides the sonar system designers a comprehensive set of tools to evaluate acoustic performance of sonar systems and the oceanographic environment in which their systems operate. The user is presented with a menu type format that helps him select parameters needed to calculate the acoustic field (transmission loss), interference field (noise and reverberation), and the system field (beam pattern and signal processing). All fields can be calculated using several models which allows the user to calculate his system performance to any degree of complexity. The system is configured to allow comparisons of calculated performance of the system or any of the component fields versus actual performance data and ascertain effects of the input parameters. Examples will be given of the performance of a line array using omni-noise field and a directional noise field and degredation of performance of the line array due to the loss of hydrophones. The effect of these different methods of hydrophone weights on system performance in different noise fields will also be demonstrated.
On the sizing of chambers for high-intensity sonic testing of space hardware
Authors: Lubman D.
Published: October 2005

Large, high-intensity sonic chambers are planned increasingly for preflight testing of space hardware. Since both capital and operating costs are closely tied to chamber size, planners have a strong incentive to select the smallest chamber size consistent with performance requirements. Current test codes and design practice appear to be inadequate for the determination of the minimum useable chamber size. This paper addresses the planner's unmet need by providing guidance for the choice of chamber size in terms of the performance penalties at low frequencies. These penalties include increased risk of undertest due to spectral voids, increased cost of sound generation due to inefficient acoustic coupling between source and chamber, and increased spatial variations of sound level due to low modal overlap. Assuming that limits are set on these parameters by program requirements, it will be shown that a planner may be guided to a reasonable and economic choice for chamber size.
Acoustics of large, enclosed audience spaces used as multipurpose auditoria
Authors: Lewitz J. A.
Published: October 2005

Many large, enclosed audience spaces (greater than 20 million cubic feet enclosed volume) which were primarily designed as sports stadia are used for a variety of programs ranging from band and orchestra performances and rock concerts to exhibit and personality shows. These spaces are truly multipurpose in use and possess unique acoustical and electronic sound-reinforcement characteristics. This paper describes several facilities along with various functions which have been accommodated. Acoustical and sound-reinforcement design solutions to the problems of successfully accommodating a wide range of events in an acoustically challenging environment are discussed.
Robust sequential detection using arrays
Authors: Dwyer Roger F.
Published: October 2005

A major problem in designing sequential detectors for array applications under varied temporally correlated noise distributions is the generalization of Wald's fundamental identity to include dependence. The approach taken is to first obtain a robust sequential detector structure for the array by partitioning the observations into known probability regions obtained from a learning sequency of independent samples from the unknown noise field. Assuming the sampling rate is increased so that the temporal samples are correlated, the data is accumulated in blocks of no samples. The block information is then processed sequentially. Using Wald's fundamental identity the probability of detection and the average sample size is obtained. It is shown that for weak signals the thresholds needed to insure the desired type I and type II errors depend upon the correlation function of the noise. However, once these thresholds are known improved performance in terms of reduced time to detection can be obtained. Data is presented which compares the performance of an array of M hydrophones for various correlation functions assuming Gaussian noise. [Work supported by Naval Material Command.]
Random and partially random acoustic arrays
Authors: Thorn J. V. , Booth N. O.
Published: October 2005

J. C. Lockwood Computer Sciences Corporation, 2251 San Diego Avenue, San Diego, CA 92110 Statistical properties of the beampatterns of three-dimensional random arrays of arbitrary geometry are derived. The class of random arrays studied differs from those previously analyzed in that it includes partially random arrays. A partially random array is defined, for purposes of this paper, as an array in which the element positions are random variables subject to constraints that create some degree of either non-randomness or interdependence. An example of a partially random array is an array in which several hydrophones are suspended in each of a large number of vertical strings. The elements are all randomly positioned, but the elements in each string lack independence in their horizontal positions. A methodology for analyzing partially random arrays is developed in which the full array is decomposed into a number of subarrays. The subarrays are chosen so that the element positions of each are independent and have the same probability density function. The properties of the random subarrays are combined to yield expressions for the expected value and variance of the pattern function of the composite partially random array. The expected value of the directivity index is also given in terms of the pattern function statistics. [Work supported by the Naval Ocean Systems Center.]
Interarray noise correlation
Authors: Berkman E. F. , Nitsche J. R.
Published: October 2005

Small amounts of residual correlated noise may degrade the tracking performance of split arrays with high values of processing gain. In the absence of directional interference, it is usually assumed that the noise output of subarrays are uncorrelated if the subarray acoustic centers are far apart relative to an acoustic wavelength. This assumption is usually justified by the fact that the correlation length for an isotropic noise field is on the order of an acoustic wavelength. However, the correlation length of the noise field after being spatially filtered by each subarray is more nearly on the order of a subarray effective aperture. Thus, one wonders if subarray noise output will have small correlation coefficients only if the acoustic centers are very well separated relative to a subarray effective aperture. For usual split array configurations, the distance between acoustic centers is equal to or only slightly greater than the effective subarray aperture. Hence, typically the interarray noise correlation is determined by the close-in side lobe structure of the interarray correlation function. We find that corresponding sidelobe levels of the interarray correlation function are usually much smaller than those of the omniphone correlation function so that small interarray noise coherency may be anticipated, even though the array acoustic centers are only slightly further apart than the characteristic correlation length of the interarray noise correlation function. The interarray noise correlation function is shown to be convolution of a) the incident noise field or omniphone correlation function and b) the auto-correlation of the subarray shading function. The implications of this relationship are examined.
Side lobe level optimization and narrow beam design using spherical homogeneous liquid lens
Authors: Fife M. E.
Published: October 2005

The theory for the focusing characteristics for an ideal homogeneous liquid lens is presented by C. A. Boyles [J. Acoust. Soc. Am. 38, 393–405) (1965)]. This paper considers the focusing characters of a lens with a limited aperture size which is controlled by the critical angle of a stiff acoustic window material. In addition, computed and measured for field beam patterns are presented for finite receivers located on the inner surface of the lens. The cases considered have d/λ >> 1 and an index of refraction between 1.85 ⩽ η ⩽ 2.17. The focused pressure distributions were obtained by brute force numerical integration over the aperture surface and the receive patterns were obtained by integrating this distribution over the surface of the receiver. Measurements were made on a 15 cm diameter lens with an ABS window material on circular and rectangular PZT-5 receive elements. The results are presented along with normalized design curves for establishing the lens parameters for multiple narrow beam lens design. These curves show optimum index of refraction values and optimum receiver sizes and lens diameter for minimum side lobe levels for a given beam width and frequency.
On the theory of a multielement array of echosonde antennas
Authors: Adekola S. Adeniyi
Published: October 2005

There is an ever-increasing interest in the use of the multielement antenna array in acoustic-radar work particularly when a single element cannot provide adequate directivity, gain and control. Specifying the following parameters: number of elements, element-spacing, and amplitude-phase excitations previously discussed [S. A. Adekola et.al., Radio Sci. 12, 11–12 (1977)], we discuss the radiation characteristics of the array. Conditions for suppressing grating lobes and secondary lobes are outlined for both end-fire and broadside acoustic arrays. Transmitting-aperture diameters of practical interest are 1.84 and 2.44 m [S. A. Adekola, J. Acoust. Soc. Am. 62, 524–542 (1977)]. For nonoverlapping array elements with one-half wavelength separation between antenna-rims, the effective distances between centres of adjacent array-elements using 1.84-m-diam apertures are 1.9 and 1.89 m for 2- and 3-kHz carrier-frequencies respectively. The corresponding values for the 2.44-m-diam. apertures are 2.61 and 2.55 m for 1- and 1.5-kHz carrier-frequencies respectively. Improved directivity for n end-fire discrete-elements is achieved by increasing the phase-lag α = 2.94/(n−1) between sources [Hansen-Woodyard, IRE, 26(3), 333–345 (1938)]. For example, the 10- and 12-array elements considered here have increased phase lags of 19° and 15° for improved-directivity respectively. Other criteria treated include: conditions for overlapping and non-overlapping array-elements, and variations of 3-dB beamwidth with the number of elements and with effective separation between elements.
Experimental measurements with a large aperture PARRAY
Authors: Goldsberry T. G. , Reeves C. R. , Rohde D. F.
Published: October 2005

A parametric acoustic receiving array (PARRAY) is characterized as a continuous, virtual end-fire array of length equal to the separation between the pump and hydrophone. Therefore, the directivity index of a PARRAY is approximately equal to 10 log (4 L/λ) where L is the pump-hydrophone separation and λ is the wavelength of the acoustic signal. A PARRAY with a pump-hydrophone separation of 340 m has been installed in 45 m of water at the Lake Travis Test Station of Applied Research Laboratories, The University of Texas at Austin. Measurements over the frequency range from 40 to 800 Hz show spatial processing gains approximating the directivity index of the PARRAY. The geometry of the experiment will be described and data obtained with the 340 m PARRAY will be presented and discussed. [This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Naval Electronic Systems Command under Contract N00039-76-C-0231.]
Experiments in acoustic imaging with an isochronal convergence imaging method
Authors: Katakura K. , Kuroda M. , Takabayashi Y.
Published: October 2005

The method used in this study employs a multi-element transducer. Each transducer element transmits successive cylindrical sound waves at a predetermined interval. During the transmission intervals, all elements receive echos from targets. A digital processor then distributes the amplitude data of these echos on elliptic addresses located in a digital memory system. The relation between sound propagation time and element location determines these elliptic addresses. The resolving power is estimated to be the same as that of a cylindrical transducer measured at the focal point for pulse-echo mode operation. The results of numerical analyses agree well with the estimated values and indicate a high resolving power within the entire imaging plane. A prototype system utilizing this method, containing a 32-element transducer and a mini computer, is used to complete some experimental imaging of stationary targets and the obtained images are discussed.
A pilot study of context effect of judged annoyance of noise
Authors: Weiler Ernest M. , Davis James M. , Pavlakos Chris
Published: October 2005

It has sometime been suggested that the same noise source is judged annoying when it interferes with one's activities, but more often judged not annoying when it is related to one's livelihood or recreational interests. The present report concerns an attempt to determine whether specification of context will correspond to certain judgmental factors of annoyance that are not accounted for by acoustic properties of noise sources. Subjects were asked to recall a specified noise source, then asked to judge whether it would be desirable or undesirable in a certain situation. Tasks were specified which were recreational or occupational. The subject role was described as depending on the noise source, neutral, or interfered with by the noise source. There was no difference between recreational and occupational tasks in terms of the rated desirability of the noise sources. Analysis of variance revealed a significant difference depending on whether the noise source was part of or interfered with the subject's task. The test technique thus agrees with some observations of annoyance factors resulting from environmental noise sources.
Body response to infrasound
Authors: Okai O. , Saito M. , Taki M. , Mochizuki A. , Fujio N. , Nishiwaki N. , Mori T.
Published: October 2005

A trial was made to investigate cardiopulmonary response to infrasound (IFS) in man and dogs whose whole body were exposed to high level (110 dB SPL) of infrasound (8–50 Hz), produced by a powerful speaker system. Experiments on man revealed that heart rate and respiratory frequency decreased by the mean values of 10% and 20% respectively but no significant tendencies existed in blood pressure during 1-min IFS exposure. On the other hand, experiments on anesthetized dogs with spontaneous respiration showed that heart rate decreased while respiratory frequency decreased slightly at first and, later, increased by more than two times of control, together with an increase in pH and oxygen content in blood, associated with a decrease in bicarbonate content in blood during two hours IFS exposure. After cessation of IFS exposure these responses gradually disappeared, i.e., the values of physiological reaction to IFS were restored to the control ones. This suggested that infrasound considerably affected the respiratory system during long IFS exposure of the whole body.
The theory of resonance scattering in acoustics, nondestructive testing, and geophysics
Authors: Überall H.
Published: October 2005

This paper summarizes recent progress concerning modal and surface-wave resonances in scattering and reflection of acoustic waves from elastic (or viscoelastic) objects, and of elastic waves from cavities or solid inclusions. Experiments and normal-mode calculations have revealed a large, often confusing variety of resonance phenomena in both acoustic and elastic-wave scattering. In collaboration with L. Flax, L. R. Dragonette, G. C. Gaunaurd, and others, we have developed a systematic theory based on the Breit-Wigner formalism of nuclear resonance scattering, in which the observed resonances can be explained physically, and interpreted in terms of the modal eigenvibrations of the elastic targets. or the contents of the cavity, respectively. Modal scattering amplitudes consist of a nonresonant background with superimposed, and interfering, resonance contributions. The latter can be isolated by subtracting the background, both in the “rigid” and the “soft” limits and in the general intermediate case. The same resonances may be viewed differently, with the mode index being considered a complex variable. This permits interpreting the scattering amplitude in terms of surface waves (“creeping waves”) corresponding to the Regge Poles of Nuclear Physics. We unify the two viewpoints, demonstrating that the resonances of the modal target eigenvibrations correspond to “phase-matching” of the creeping waves, which occurs when the target's circumference measures an even (for cylinders) or odd (for spheres) integer number of half-wave lengths. [Supported by ONR Code 421.]
Rayleigh and Lamb wave resonances in an elastic plate
Authors: Fiorito R. , Madigosky W. , Überall H.
Published: October 2005

Our preliminary analysis [R. Fiorito, W. Madigosky and H. Überall, J. Acoust. Soc. Am. 62, S83(A) (1977)] of the acoustic properties of fluid-loaded elastic plates employing a resonance theory commonly used in nuclear physics. and recently applied to acoustic scattering [see, e.g., L. Flax, L. R. Dragonette and H. Überall, J. Acoust. Soc. Am. 63, 723 (1978)] has been completed, and numerical results for the resonance positions and widths of Rayleigh and Lamb modes in the acoustic reflection and transmission coefficients of a steel plate immersed in water have been obtained as functions of frequency-thickness or angle of incidence. Using resonance formalism, we have been able to explain analytically the previous empirical findings of Pitts et al. [L. E. Pitts, T. J. Plona, and W. G. Mayer, J. Acoust. Soc. Am. 60, 374 (1976)], regarding the frequency dependence of the positions of the poles and zeros of the reflection coefficient in the complex angle plane. Our resonance formalism has the added advantage of employing purely real equations (even for the case of fluid loading) to calculate the real and imaginary parts of pole and zero positions, hence allowing a great computational simplification. [H. Ü. is also at Catholic University and is supported in part by ONR, 421.]
Selective elevation of cochlear whole-nerve thresholds for high frequencies recorded acutely in guinea pigs
Authors: Hawkins J. E. , Cazals Y. , Erre J.-P. , Aran J.-M.
Published: October 2005

Whole-nerve responses to filtered clicks were recorded in guinea pigs still under ketamine anesthesia after a wire electrode had been placed on the round-window membrane through a small drill-hole and the bulla re-sealed. Comparison with recordings made in waking animals several days after a similar operation [Aran and Erre, in Technological Bases of Auditory Investigation, edited by H. A. Beagley (Oxford, in press)] showed that in the anesthetized animals thresholds for the highest frequencies (16–40 kHz) had been elevated and latencies above 2 kHz increased. After recovery from anesthesia these responses returned to normal in about one week. When other animals already equipped with a round-window electrode were anesthetized, a similar but less-marked threshold shift sometimes occurred, without increase in latency. The observations emphasize the susceptibility of the most basal portion of Corti's organ to adverse conditions, including both anesthesia and operation. Thus acute recordings made under anesthesia may not reveal true neural thresholds for high frequencies. [Work supported by INSERM.]
Comparison of Impact noise and continuous noise on cochlear function
Authors: Salt A. N. , Konishi T. , Akay A. , Cook R.
Published: October 2005

Acute guinea pig preparations have been exposed to noise produced by a mechanical impact noise generator. Impacts were at a rate of 1/s and produced a peak sound pressure level of 130 dB at the preparation. Exposure periods of 20 min were used. Cochlear potentials in response to 6-kHz tone bursts were recorded from differential electrodes in the basal cochlear turn. The extent of suppression and the time courses of decline and recovery associated with exposure to impact noise were measured. These results were compared with those occurring after exposure to continuous broad band white noise at an intensity such that the same total energy was delivered to the preparation over a similar 20 min period. Tone induced responses were found to be suppressed to a greater extent by impact noise although the recovery from this exposure was more rapid. The dependence of response suppression on the rate of impacts or peak intensity has also been investigated.
Effects of exposure to noise on electrolyte transport in the guinea pig cochlea
Authors: Konishi Teruzo , Salt A. N. , Hamrick P. E.
Published: October 2005

Electrolyte transport (K+, Na+, and Cl−) across the endolymphperilymph barrier in guinea pigs exposed to broad band white noise was studied by perfusing the perilymphatic space with artificial perilymph containing K43, Na22, or Cl36 and measuring the uptake of these isotopes into the endolymph. Exposure to broadband white noise at 105 dBA for 7 days resulted in a substantial loss of cochlear microphonics sensitivity measured at 6 KHz, while the endocochlear potential was slightly higher than that obtained in control animals. The K+ and Na+ concentrations in the endolymph were 159.6 and 0.68 mM, respectively. These estimates were within the range normally observed. The Cl− concentration in the endolymph was 138.1 mM. Our data showed that the uptake of K43, Na22 and Cl36 into the endolymph could be represented by a single exponential curve dependent on the perfusion time, the rate constants after noise exposure at 105 dBA being 0.009, 0.019, and 0.011 min−1 for K+, Na+, and Cl−, respectively. Our results indicated that this noise exposure resulted in a decrease of the rate constant for K+ uptake.